Studies on the synthesis of anti-cholinergic drug...

Chapter V

O

O

OH

N .Br

Studies on the synthesis of

anti-cholinergic drug,

Glycopyrrolate

INTRODUCTION:

Glycopyrrolate is used in combination with other medications to treat ulcers. Glycopyrrolate is

in a class of medications called anticholinergics. It decreases stomach acid production by

blocking the activity of a certain natural substance in the body.

An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in

the central and the peripheral nervous system. Anticholinergics inhibit parasympathetic nerve

impulses by selectively blocking the binding of the neurotransmitter acetylcholine to its receptor

in nerve cells. The nerve fibers of the parasympathetic system are responsible for

the involuntary movement of smooth muscles present in the gastrointestinal tract, urinary

tract, lungs, etc. Anticholinergics are divided into three categories in accordance with their

specific targets in the central and/or peripheral nervous system: antimuscarinic agents,

ganglionic blockers and neuromuscular blockers.

Glycopyrronium bromide is a medication of the muscarinic anticholinergic group. It does not

cross the blood–brain barrier and consequently has no to few central effects. A synthetic

http://en.wikipedia.org/wiki/Neurotransmitter

http://en.wikipedia.org/wiki/Acetylcholine

http://en.wikipedia.org/wiki/Central_nervous_system

http://en.wikipedia.org/wiki/Peripheral_nervous_system

http://en.wikipedia.org/wiki/Parasympathetic

http://en.wikipedia.org/wiki/Nerve_cell

http://en.wikipedia.org/wiki/Nerve_fiber

http://en.wikipedia.org/wiki/Involuntary_motion

http://en.wikipedia.org/wiki/Gastrointestinal_tract

http://en.wikipedia.org/wiki/Urinary_tract

http://en.wikipedia.org/wiki/Urinary_tract

http://en.wikipedia.org/wiki/Lungs

http://en.wikipedia.org/wiki/Antimuscarinic

http://en.wikipedia.org/wiki/Ganglionic_blockers

http://en.wikipedia.org/wiki/Neuromuscular-blocking_drug

http://en.wikipedia.org/wiki/Medication

http://en.wikipedia.org/wiki/Muscarinic

http://en.wikipedia.org/wiki/Anticholinergic

http://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier

MD. UMAR KHAN Thesis

Studies on the synthesis of anti-cholinergic drug, Glycopyrrolate 361

Chapter - V

quaternary amine, it is available in oral and intravenous (I.V.) forms. It was developed by Sosei

and licensed to Novartis in 2005. The cation, which is the active moiety, is also known

as glycopyrrolate.[1]

Table-5.1

Adrenergics,

inhalants

Short acting β2-agonists (Salbutamol, Fenoterol, Terbutaline, Pirbuterol,

Procaterol, Bitolterol, Rimiterol, Carbuterol, Tulobuterol, Reproterol)

Long acting β2-agonists (Arformoterol, Bambuterol, Clenbuterol,

Formoterol, Salmeterol, Ultra LABA, Indacaterol)

Other (Epinephrine, Hexoprenaline, Isoprenaline, Orciprenaline)

Glucocorticoids Beclometasone, Budesonide, Ciclesonide, Fluticasone, Mometasone,

Flunisolide, Betamethasone, Triamcinolone

Anticholinergic

s/Muscarinic

antagonist

Aclidinium bromide, Glycopyrronium bromide, Ipratropium bromide,

Oxitropium bromide, Tiotropium bromide

Mast cell

stabilizers Cromoglicate, Nedocromil

Xanthines Doxofylline, Enprofylline, Theobromine, Theophylline/Aminophylline

Eicosanoid

inhibition

Leukotriene antagonists (Montelukast, Pranlukast, Zafirlukast)

Lipoxygenase inhibitor (Zileuton)

Thromboxane receptor antagonists (Ramatroban, Seratrodast)

Combination

products

Budesonide/formoterol, Fluticasone/salmeterol, Ipratropium

bromide/sulbutamol, Mometasone/formoterol

Glycopyrronium blocks muscarinic receptors,[2]

thus inhibiting cholinergic transmission.

In anesthesia, glycopyrronium injection can be used as a preoperative medication in order to

reduce salivary, tracheobronchial and pharyngeal secretions, as well as decreasing the acidity of

gastric secretion. It is also used in conjunction with neostigmine, a neuromuscular blocking

reversal agent, to prevent neostigmine's muscarinic effects such as bradycardia.

Glycopyrrolate is used for reducing secretions in the mouth, throat, airway and stomach before

surgery. It is used before and during surgery to block certain reflexes and to protect against

http://en.wikipedia.org/wiki/Amine

http://en.wikipedia.org/wiki/Novartis

http://en.wikipedia.org/wiki/Cation

http://en.wikipedia.org/wiki/Moiety_(chemistry)

http://en.wikipedia.org/wiki/Glycopyrronium_bromide#cite_note-pmid17459043-1

http://en.wikipedia.org/wiki/Muscarinic_receptor

http://en.wikipedia.org/wiki/Glycopyrronium_bromide#cite_note-pmid10385241-2

http://en.wikipedia.org/wiki/Cholinergic

http://en.wikipedia.org/wiki/Anesthesia

http://en.wikipedia.org/wiki/Injection_(medicine)

http://en.wikipedia.org/wiki/Saliva

http://en.wikipedia.org/wiki/Tracheobronchial

http://en.wikipedia.org/wiki/Acidity

http://en.wikipedia.org/wiki/Neostigmine



http://en.wikipedia.org/wiki/Bradycardia



Chapter - V

certain side effects of some medicines. It is also used along with other medicines to treat peptic

ulcers.

Table-5.2

Sr.

no.

Generic name

Systematic (IUPAC) name Structure

1

Glycopyrronium bromide (1)

3-(2-cyclopentyl-2-hydroxy-2-

phenylacetoxy)-1,1-

dimethylpyrrolidinium bromide

O

O

OH

N.Br

2

Aclidinium bromide (2)

[(8R)-1-(3-phenoxypropyl)-1-

azoniabicyclo[2.2.2]octan-8-yl] 2-

hydroxy-2,2-dithiophen-2-ylacetate

bromide O

NO

O

HO S

S .Br

3

Ipratropium bromide (3)

[8-methyl-8-(1-methylethyl)- 8-

azoniabicyclo[3.2.1] oct-3-yl] 3-hydroxy-

2-phenyl-propanoate bromide O

OH

.BrO

N

4

Oxitropium bromide (4)

(8r)-6β,7β-Epoxy-8-ethyl-3α-hydroxy-

1αH,5αH-tropanium bromide (-)-tropate

bromide O

O

N

O

OH

.Br

5

Tiotropium bromide (5)

(1α,2β,4β,7β)-7-[(hydroxidi-2-

thienylacetyl)-oxy]-9,9-dimethyl-3-oxa-9-

azoniatricyclo-[3.3.1.02,4

]nonane bromide

O

O

HOS

S .Br

N

O

It is also used to reduce excessive saliva (sialorrhea).[3-5]

It decreases acid secretion in

the stomach and so may be used for treating stomach ulcers, in combination with other

medications. Use in treating asthma[6-7]

and COPD[8]

has been described. It has been used

topically and orally to treat hyperhidrosis.[9-10]

http://en.wikipedia.org/wiki/Saliva

http://en.wikipedia.org/wiki/Sialorrhea

http://en.wikipedia.org/wiki/Acid

http://en.wikipedia.org/wiki/Secretion

http://en.wikipedia.org/wiki/Stomach

http://en.wikipedia.org/wiki/Peptic_ulcer

http://en.wikipedia.org/wiki/Asthma

http://en.wikipedia.org/wiki/Chronic_obstructive_pulmonary_disease

http://en.wikipedia.org/wiki/Chronic_obstructive_pulmonary_disease

http://en.wikipedia.org/wiki/Hyperhidrosis



Chapter - V

Glycopyrrolate is a quaternary ammonium salt with the following chemical name: 3-

[(cyclopentyl-hydroxyphenylacetyl)oxy]-1,1-dimethyl pyrrolidinium bromide. The molecular

formula is C19H28BrNO3 and the molecular weight is 398.33. Its structural formula is as follows:

O

O

OH

N.Br

As seen in the above structural formula, Glycopyrrolate molecule has two chiral centres and can

have four stereo isomers, that is two enantiomeric pairs of diastereoisomers. Glycopyrrolate is a

racemic mixture containing only one pair of enantiomers. Commercially available

Glycopyrrolate contains both the (R,S)-Glycopyrrolate and (S,R)-Glycopyrrolate enantiomers.

Glycopyrrolate occurs as a white, odorless crystalline powder. It is soluble in water and alcohol,

and practically insoluble in chloroform and ether.

REVIEW OF LITERATURE:

Number of methods has been developed for racemic and asymmetric synthesis of

Glycopyrrolate. The existing asymmetric synthesis of Glycopyrrolate involves use of Mandelic

acid as key raw material[11-12]

and chiral auxilary induced Grignard addition on

phenylglyoxalate.[13]

Process, in which racemic Glycopyrrolate is the product, (intermediates of

them) were prepared by making Grignard reagent of cyclopentadienyl magnesium bromide,[14-15]

or cyclopentyl magnesium bromide,[16-22]

and addition to methyphenylglyoxalate. Using an

inverse approach, the phenyl Grignard reagent is reacted with cyclopentyl-glyoxylic acid

ester.[23-24]

Glycopyrrolate can also be prepared by oxidation of intermediates[25-27]

and by trans

esterification with 1-methyl-3-pyrrolidinol[28-33]

and subsequently, quarternization with methyl

bromide.[34-40]



Chapter - V

O

O

OH

HON

O

O

OH

NO

O

OH

NH

O

O

OH

N.Br

1

Na / Heptane

3N HCl

NaOHCl

H3C Br

methyl ethyl ketone

24h / rt

crystallisation

methanol/butanone

1 (mixture RS/SR and RR/SS-diastereomers)

(RS/SR mixture)

6

7

8

9

8x

…..Scheme-5.1

Glycopyrrolate 1 was first synthesized by Lunsford in 1960.[28]

The key intermediate for its

synthesis was the ester 8 of cyclopentyl mandelic acid 6 with 1-methyl-3-pyrrolidinol 7.

Desmethyl Glycopyrrolate 8 was prepared by transesterification of methyl cyclopentyl-

mandelate 6 and 7 in the presence of metallic sodium or sodium hydride (Scheme-5.1). As a

tertiary amine, the Desmethyl Glycopyrrolate 8 can be purified by extraction of its salt 3x into

water to remove impurities followed by back extraction into an organic solvent.

The final step of the synthesis was N-methylation of 8 using methyl bromide 9 to form the solid

quarternary ammonium salt 1. As 1 is a mixture of two pairs of enantiomers which were

separated by final repeated recrystallization to get the desired RS / SR-diastereomer mixture of

1 with 16% overall yield starting from methyl cyclopentylmandelate 6.

Baxter et al[38]

followed the same synthetic scheme as reported by Lunsford. They developed a

method for the production of crystalline glycopyrronium bromide 1 (Scheme-5.2), which

comprises the reaction of glycopyrronium base with methyl bromide in a solvent, in which the

solvent was selected such that the diastereoisomeric ratio of the product favours the R,S and S,R



Chapter - V

diastereoisomers over the R,R, and S,S diastereoisomers, and separating the desired

diastereoisomers by one or more controlled crystallisation steps. This method gives a product

having a particle size of narrow distribution and 20% overall yield starting from cyclopentyl

mandelic acid 10.

10

O

O

OH

HON

O

O

OH

NNa / Heptane

6

7

8

OH

O

OH SOCl2 / MeOH

H3C Br 9(g)

acetone

1

(mixture RS/SR and

RR/SS-diastereomers)

MeOH / methyl ethyl ketone

O

O

OH

N.Br

1 (RS/SR mixture)

1st crystn.

2nd crystn.

3rd crystn.

…..Scheme-5.2

Bodor et al[32]

repeated the process (Scheme-5.3) and obtained desmethyl Glycopyrrolate 8 in

16% overall yield from phenylglyoxylic acid 11.

11 1210

O

O

OH

HON

O

O

OH

NNa / Heptane

6

7

8

OH

O

OHOH

O

O

MgBrEt2O, 0°C

24h / rt+

CH3I,

K2CO3, DMF

2h / rt

…..Scheme-5.3

Thomas et al[14]

described that the use of cyclopentyl Grignard reagents gives poor yields of the

desired methyl cyclopentyl mandelate 6. Their invention relates to a novel method for the

production of methyl cyclopentyl mandelate 6 employing the use of cyclopentadienyl or lower



Chapter - V

alkyl substituted cyclopentadienyl Grignard reagents and hydrogenation techniques (Scheme-

5.4). The cyclopentadienyl Grignard reagent used in the first stage of applicants process was a

well known reagent. Reported yield of this single step was 86%, with 98% HPLC purity.

13 14

250-300°C

Exothermic

ethyl magnesium bromide

diethyl ether, toluene

90-100°C

MgBr

O

O

O MgBr

+

Toluene-ether

acid / base

MeOH-AcOH

10% Pd-C / H2

O

O

OH

6

1415

16 15

…..Scheme-5.4

Biel et al[41]

prepared 10 by reacting methyl phenylglyoxalate 16 and cyclopentyl magnesium

bromide 12 to form the ester 6 which was hydrolyzed and purified (Scheme-5.5) with 28%

overall yield.

O

O

O

+Toluene-ether

O

O

OH

616 12

MgBr

10

OH

O

OH

…..Scheme-5.5

Blumbergs et al[26]

used cyclopentyl phenyl ketone 18 and DCM which were reacted at very low

temperature with n-Butyl lithium. Obtained dichloro compound 19 was converted to 10 by

hydrolysis and successive oxidation as given in Scheme-5.6 in 16% overall yield.



Chapter - V

17 18 19

20

OCl

O

OH

Cl

Cl

OH

O

H

10

OH

O

OH

AlCl3, Benzene

1h / reflux THF, n-BuLi

-100°C, H2SO4

K2CO3,

IPA:water (1:1)

19h / rt

Dioxane,

KMnO4, water

CH2Cl2

…..Scheme-5.6

Adam et al[27]

reacted cyclopentyl phenyl acetic acid 21 with n-Butyl lithium at -40°C and then

with oxygen results 10 (Scheme-5.7).

21

OH

O

HOLi

O

Li

OH

O

OH

1022

n-BuLi, THF, -40°C O2, rt

…..Scheme-5.7

Grover et al[12]

reported a diastereoselective synthesis of cyclopentyl mandelic acid 28.

Mandelic acid 23 was protected with pivalaldehyde in pentane. Obtained chiral dioxolane 24

reacted at very low temperature with cyclopentenone in THF in presence of LHMDS, followed

by elimination, hydrolysis and reduction yields 28 in 60% overall yield with 99.9% ee.

OH

O

OH

O

O

O

O

O

O

HO

O

O

OOH

O

OHOH

O

OH

23

24 25

26 2728

Pivalaldehyde, pentane

Tf-MSA, 5.5h / reflux

NaHCO3

THF, LHMDS

-78°C, 1h

cyclopentanone

THF, 0°C,

SOCl2, pyridine

KOH, water / methanol

heptane / reflux

methanol

10% Pd / C

1 atm, 18h

heptane

…..Scheme-5.8



Chapter - V

PRESENT WORK:

The object of the present work was to uncover and overcome the many disadvantages of the

prior art. This work deals with 4-step preparation of Glycopyrrolate, having process control via

Barbier reaction for the preparation of 6, hydrolysis, esterification, trans-esterification and

finally quaternization of amine for the large scale synthesis of 1 (Scheme-5.9). Present work

details the journey towards development of a simple, safe, productive, eco-friendly and easy to

handle commercial process for preparing Glycopyrrolate. Hence, we have developed and

optimized the process, impurities formed in the process were identified, prepared and

characterized. Additionally, force degradation study of Glycopyrrolate was also investigated. A

mechanistic rationale for the formation of the various process impurities and degradation

products has been provided.

O

O

O

+

16

BrMg, I2, THF

O

O

OH

6 10

OH

O

OHHydrolysis MeOH, HCl

O

O

OH

6

12

HON

NaOMe

Heptane

7O

O

OH

N

8

H3C Br 9

IPA, MTBE

O

O

OH

N.Br

1 (RS/SR mixture)

AcOH, water Toluene

…..Scheme-5.9

RESULTS AND DISCUSSION:

Preparation Of Glycopyrrolate Hydroxy Acid: We have selected Methyl phenyl glyoxylate

(Methyl 2-oxo-2-phenylethanoate), 16 as the starting material in the preparation of

Glycopyrrolate hydroxy ester, 6 which was the key intermediate to prepare Glycopyrrolate.

This starting material was commercially available and can be procured easily.



Chapter - V

Preparation of 6 by Grignard reaction has been described in literature,[41]

wherein Grignard

reagent of 12 has been prepared first and then added to 16. Thereafter, obtained product was

purified by column chromatography, which was a tedious process on large scale.

As a part of process development, we have also started work by preparing Grignard reagent of

12. To prepare 6, the Grignard reagent of 12 (1.2 m. eq.) was prepared as usual by reacting it

with magnesium in tetrahydrofuran / diethyl ether. It was added to 16 (1 m. eq.) in

tetrahydrofuran and the reaction was monitored by qualitative HPLC, which showed 23.10% of

the unreacted methyl phenyl glyoxylate 16 and several other impurities. In the same reaction

25% more Grignard reagent (total 1.55 m. eq.) was added, the starting material left unreacted

was 3.31%. However, formation of product 6 was only 36.5% by qualitative HPLC.

Subsequent to this experiment, one more experiment was repeated wherein 1.2 m. eq. of

Grignard reagent of 12 and 1.2 m. eq. of tetrabutyl ammonium bromide was used. In this

reaction, 16 left unreacted was 0.81% but again a large no. of impurities were seen in HPLC

chromatogram. Formation of the 6 was only 36.19% by qualitative HPLC.

Thereafter, 1.2 m. eq. of Grignard reagent of 12 was prepared in tetrahydrofuran-toluene and

added to 16 diluted in toluene at 25-30°C. This reaction again resulted in formation of only

30.56% of 6 after isolation. Another experiment was carried out using 1.2 m. eq. Grignard

reagent, prepared in diethyl ether and added to 16 taken in 2-methyltetrahydrofuran at 20-25°C

in 1 h. This reaction resulted in a unreacted methyl phenyl glyoxylate 16, 25.86% with 23.63%

product during reaction monitoring. In all the above experiments, two major impurities were

formed and later identified as methyl mandelate and Bismethyl mandelate as shown below.

O

O

OHHO

O

HO

O

O

OH

29

30



Chapter - V

The plausible mechanism for the formation of these impurities are shown in Scheme-5.10 and

Scheme-5.11.

31

O

O

O

+

16

MgBr

12

H

O

O

OMgBrH

+

O

O

OHH

29

O

O

HO

O

O

OH

30

…..Scheme-5.10

O

O

OMgBrH

O

O

OMgBr

O

O

O

31

-

O

O

HO

O

O

OH

30

O

O

OHH

29

…..Scheme-5.11

Based on the above study, it seems that these impurities were inevitable to form in Grignard

reaction due to the formation of unstable Grignard reagent. Therefore, to minimize the reaction

steps/time, which was the main cause for these impurities formation, we have taken methyl

phenyl glyoxylate and cyclopentyl bromide in one pot and reacted with magnesium turnings at

35-40°C to make Glycopyrrolate hydroxy ester (Barbier Reaction),[42]

which was thereafter

hydrolyzed to its acid derivative for purification. By this way got the Glycopyrrolate hydroxy

acid having a purity of 90% by qualitative HPLC analysis. Practically, there was no loss of

product during hydrolysis reaction simultaneously. By the above process it was clear that there

was no need to make Grignard reagent separately.



Chapter - V

The compound of formula 16 and cyclopentyl bromide were reacted with magnesium under

Barbier conditions in an inert organic solvent to give compound of Formula 6. The inert

organic solvents were selected from tetrahydrofuran, n-hexane, n-heptane, toluene or

mixture thereof, preferably tetrahydrofuran. After completion of the reaction, reaction

mixture was diluted with water and extracted with toluene, concentrated to give a residue

containing the compound of Formula 6 as an oily mass. This oily mass was treated with

aqueous base in an organic solvent to give compound of Formula 10. The aqueous base can

be selected from sodium hydroxide, potassium hydroxide, preferably sodium hydroxide.

The organic solvent employed was selected from methanol, ethanol, isopropyl alcohol,

preferably methanol. The pH of the aqueous layer was adjusted to 1.8-2.2 with HCI to

precipitate the product. Finally, the product obtained was filtered and further purified by re-

crystallization from acetonitrile. The compound of Formula 6 is insitu hydrolysed to give

compound of Formula 10.

Some Barbier reaction experiments have been carried out using 1.2 m. eq. of 12 and magnesium

1.5 m. eq. per mole of methyl phenyl glyoxylate 16 and emphasis was on that to minimize the

starting material. Second, by hydrolysis of 6 to 10 routinely eliminate the impurities given

above (29 and 30), as these were highly soluble in water. This way, we succeed to obtain the 10

having more than 90% HPLC chromatographic purity (Table-5.3).

Table-5.3

BATCH NO. CHROMATOGRAPHIC

PURITY ASSAY (By titrimetry)

SRK(660)57 93.62% 96.8%

MK(657)96 93.16% 96.6%

MK(657)98 94.04% 96.8%



Chapter - V

Detection and origin of impurities during preparation of 10: Eight process impurities were

detected by LCMS with a mass of 150, 122, 218, 164, 220, 234, 152 and 288. The structures 11,

32, 33, 16, 35, 6, 23 and 36 were proposed for these compounds (Table-5.4). Origin of these

impurities is briefly described in Scheme-5.12.

Table-5.4

11

OH

O

O

32

O

OH

33

OH

O

OH

O

O

O

16

35

OH

O

OH

O

O

OH

6

OH

O

OH

23 36

OH

O

OH

Impurity 11 thought to arise due to hydrolysis of unreacted 16 during preparation of 10.

Mandelic acid, 23 originates due to reduction of 16 during Barbier reaction as shown in

Scheme-5.10, whereas, 35 may form by reacting Grignard adduct with 12 (Scheme-5.12).

Mechanism for the formation of 32 are not clear as it may involve complex free radical

mechanism.[21]

O

O

O

+

16

BrMg, I2, THF

O

O

OH

6 10

OH

O

OHHydrolysis

12

AcOH, water

11

OH

O

O

hydrolysisO

O

OMgBrH

reduction

12

35

OH

O

OHhydrolysis

hydrolysis

OH

O

OH

23

…..Scheme-5.12



Chapter - V

Impurity 33, may originate due to dehydrohalogenation of cyclopentyl bromide, 12 followed by

bromination through free radical reaction to obtain a 3-bromocyclopent-1-ene and which may

carry further reaction with 16 in presence of magnesium turnings to form alkene glycopyrrolate

hydroxy ester 37. The reaction sequence shown in Scheme-5.13.

31

Br

12 Br

MgBr

O

O

O

16 O

O

OH

37 33

OH

O

OHHydrolysis MeOH, HCl

Toluene

O

O

OH

37

HON

NaOMe

Heptane

7O

O

OH

N

41

H3C Br 9

IPA, MTBE

O

O

OH

N.Br

45 (RS/SR mixture)

DehydrohalogenationBromination through

free radical Mg

…..Scheme-5.13

As reduction and enolization are the common byproducts of Grignard reaction, reduction leads

to 23 and 35. Enolization, as described in scheme-5.14, may result in 36. Preparation of these

impurities are given in experimental section.

O

O

O

+

16

BrMg, I2, THF

12

O

O

O

MgBr

O

O

H

OMgBr

O

O

OHO

O

O

BrMg, I2, THF

12

+ OH

O

OH

36

…..Scheme-5.14



Chapter - V

Preparation Of Glycopyrrolate Hydroxy Ester: Esterification of Glycopyrrolate hydroxy acid is

a facile reaction. Esterification can be carried out by using thionyl chloride/methanol,

methanolic hydrochloric acid etc. The compound of Formula 10 was esterified by using

methanolic HCI in inert organic solvent selected from toluene, xylene, hexane, cyclohexane,

preferably toluene to give a compound of Formula 6. The Glycopyrrolate hydroxy acid of

Formula 10 was dissolved in toluene and subjected to esterification using methanolic HC1 at

ambient temperature. After completion of the reaction, reaction mixture was cooled to 20-25°C

and product was extracted into toluene. The toluene extract was washed with sodium

bicarbonate and concentrated under reduced pressure to give compound of Formula 6. Normally

in the prior art process thionyl chloride was used for esterification. However, in the present

process methanolic HC1 was used. The tedious job of distilling off excess thionyl chloride was

avoided thereby making the process less hazardous.

Esterification in laboratory was carried out using 18.22% w/w freshly prepared hydrogen

chloride solution in methanol at 55-60°C and reaction was over in ~8 h to produce

Glycopyrrolate hydroxy ester. By using hydrogen chloride in methanol, the tedious job of

distilling excess of thionyl chloride was avoided here by making the process less hazardous. In

the HPLC Chromatogram, no major impurity formation was observed during this esterification

reaction. After completion of reaction, reaction mass was washed with 5% w/w aqueous

sodium bicarbonate solution to remove un-reacted Glycopyrrolate hydroxy acid and obtained

toluene layer was concentrated to yield product, Glycopyrrolate hydroxy ester. Glycopyrrolate

hydroxy ester, thus obtained usually has HPLC Chromatographic purity 94%, assay ~98%

w/w, analyzed with ~2% in toluene.

Detection and origin of impurities during preparation of 6: In this stage, four potent impurities

were observed (Table-5.5). 16 was the carryover raw material, whereas 10 was unreacted stage-

I product. 37 and 39 are again carryover impurities of 33 and 36. Preparation of these impurities

are given in experimental section.



Chapter - V

Table-5.5

O

O

O

16 10

OH

O

OH

37

O

O

OH

39

O

O

OH

Preparation Of Desmethyl Glycopyrrolate: Number of methods are reported to make

substituted phenylglycolate. Here, it was not possible to react free acid with 3-chloro-1-

alkylpyrrolidine in 2-propanol due to the surprising stability of 3-chloro-1-alkylpyrrolidine.[43]

Therefore, transesterification was the simplest way to prepare Desmethyl Glycopyrrolate 8.

Methyl ester of Glycopyrrolate hydroxy acid 6 was preferred to react with 1-methyl-3-

pyrrolidinol 7 in presence of sodium methoxide, in this reaction methanol was formed as by-

product. So, it was important to remove methanol from the reaction to push the reaction in

forward direction.

Based on information, we tried toluene as a solvent in transesterification reaction. This reaction

was carried out using 1.3 m. eq. of 1-methyl-3-pyrrolidinol, 7 and 0.15 m. eq. sodium

methoxide per mole of Glycopyrrolate hydroxy ester 6. After 3 h of reaction, 8 was formed

only 28.44% while starting material 6 was 42.32%. Formation of Glycopyrrolate hydroxy acid

10 was ~20%, as observed in this experiment, which can be due to hydrolysis of product in

basic environment.

Another experiment of transesterification was carried out by using freshly prepared sodium

methoxide in methanol (0.15 m. eq.), n-heptane as a solvent and 1-methyl-3-pyrrolidinol

1.3 m. eq. per mole of Glycopyrrolate hydroxy ester. This reaction does not proceeded in

forward direction after some time, may be due to excess of methanol.

Methanol, having excellent azeotropic data with n-Heptane was preferred as a solvent for trans-

esterification reaction. For that, simultaneous addition of n-heptane was must to maintain the



Chapter - V

volume of reaction mass. In other experiment, 1.2 m. eq. of 1-methyl-3-pyrrolidinol and 0.10 m.

eq. of sodium methoxide per mole of Glycopyrrolate hydroxy ester 6 was used in transes-

terification reaction. But after attaining unreacted starting material i.e. Glycopyrrolate hydroxy

ester 7.68%, the reaction does not processed further. The product, Desmethyl Glycopyrrolate in

the reaction was 71.63%. After workup the yield obtained was 0.82 w/w based on input. Based

on these observations, attempts were made to push forward transesterification reaction until

Glycopyrrolate hydroxy ester was ≤ 5.0%. To achieve this, the obvious choice was to increase

the molar quantity of 1-methyl-3-pyrrolidinol reactant. A transesterification reaction was

carried out using 1.3 m.eq. 1-methyl-3-pyrrolidinol and 0.15 m. eq. Sodium methoxide. This

reaction has taken one hour to attain unreacted Glycopyrrolate hydroxy ester 4.60%.

Another transesterification reaction was repeated using 1.5 m. eq. of 1-methyl-3-pyrrolidinol

and 0.15 m. eq. of sodium methoxide. This reaction also resulted 3.32% unreacted

Glycopyrrolate hydroxy ester in 2 h of reaction. The two major impurities were observed during

reaction monitoring, which were later identified as:

18

O

10

OH

O

OH

Glycopyrrolate hydroxy acid can be formed due to alkaline hydrolysis of Desmethyl

Glycopyrrolate 8 or Glycopyrrolate hydroxy ester 6, while cyclopentyl phenyl ketone impurity

can be formed as shown in Scheme-5.15.

40

O

O

OH

N

8 18

O + CO2 +N

…..Scheme-5.15



Chapter - V

This impurity increases after attaining unreacted Glycopyrrolate hydroxy ester 5% in reaction

monitoring when heating of the reaction mass was continued thereafter.

Having understood the nature of major impurities present in reaction mass, a work-up procedure

was followed wherein Desmethyl Glycopyrrolate having basic amino group in its structure was

extracted into water as hydrochloride salt. This practice would routinely remove cyclopentyl

phenyl ketone, Glycopyrrolate hydroxy acid and Glycopyrrolate hydroxy ester impurities as

these were unable to make hydrochloride salt because of absence of amino group in their

structure and would remain in organic layer.

It was observed that impurities present at RRT ~0.76 and RRT~0.83 did not decrease in work-

up and thereafter carried forward in the next step i.e. in the formation of Glycopyrrolate. Later

these impurities (diastereomeric mixture) were also identified having the following structure:

41

O

O

OH

N

The compound of Formula 6 was transesterified with a compound of Formula 7 by using a base

like sodium methoxide in presence of inert organic solvent selected from toluene, xylene,

heptane, preferably n-heptane to give 8 and a diastereomeric mixture of compounds of Formula

41. After completion of the reaction, reaction mass was diluted with aqueous hydrochloric acid,

washed with toluene and adjusted pH of the aqueous layer to 9.0-9.2 with aqueous ammonia.

The product was extracted into toluene and thereafter toluene was evaporated to give 8 and a

diastereomeric mixture of compounds of Formula 41. This condensation was performed using

sodium methoxide in place of strong bases like Na metal or sodium hydride, which were

hazardous to handle.

During the above mentioned condensation of compound of Formula 6 with compound of

Formula 7, a mixture of two products 8 and 41 formed. The compounds 41 was by product and

difficult to remove by crystallization. In order to solve this problem, we thought that instead of



Chapter - V

eliminating this compound by purification methods that were difficult, it was all the more

advantageous to convert that impurity back to compound of Formula 8. So the same solution of

Formula 41 was hydrogenated using a catalyst in a solvent selected from C1-6 alcohols, CI-6 alkyl

acetates or mixtures thereof. The C1-C6 alcohol was selected from the group consisting of

methanol, ethanol, propanol and isopropanol, preferably in methanol at 20-30°C with a pressure

of 40-60 psi. The catalyst was selected from palladium, platinum, rhodium, ruthenium and raney

nickel, preferably palladium on carbon. After completion of the reaction, the catalyst was

removed by filtration and filtrate was concentrated under reduced pressure to yield compound of

Formula 8 in quantitative yield.

Presence of Alkene Desmethyl Glycopyrrolate 41 in Desmethyl Glycopyrrolate 8 and in

Glycopyrrolate 1 are given in Table-5.6.

Table-5.6

DESMETHYL

GLYCOPYRROLATE

GLYCOPYRROLATE

(CRUDE)

GLYCOPYRROLATE

BATCH NO. RRT

0.76

RRT

0.83 BATCH NO.

RRT

0.60

RRT

0.70 BATCH NO.

RRT

0.60

RRT

0.70

MK(657)102 0.26 0.16 SRK(660)75 0.17 0.15 SRK(660)78 0.11 0.14

MK(657)104 0.39 0.24 SRK(660)80 0.23 0.24 SRK(660)84 0.10 0.21

MK(657)106 0.42 0.27 SRK(660)82 0.31 0.27 SRK(660)83 0.15 0.23

This was very clear that this Alkene Desmethyl Glycopyrrolate was not eliminating in mother

liquor even after its quarternization reaction with methylbromide. So, there was a need to

eliminate this impurity in this step only. We have developed a process, wherein this Alkene

Desmethyl Glycopyrrolate has been converted to Desmethyl Glycopyrrolate. This process

comprises hydrogenation of Desmethyl Glycopyrrolate having Alkene Desmethyl

Glycopyrrolate with palladium on charcoal. Results of some batches are given in Table-5.7.



Chapter - V

Table-5.7

BEFORE HYDROGENATION AFTER HYDROGENATION

BATCH NO. RRT ~0.70 RRT ~0.83 BATCH NO. RRT ~0.70 RRT ~0.83

MK(657)137 0.55 0.29 MK(657)137 Not detected Not detected



Detection and origin of impurities during preparation of 8: Glycopyrrolate hydroxy acid 10

can be formed due to alkaline hydrolysis of Desmethyl Glycopyrrolate 8 or Glycopyrrolate

hydroxy ester 6. 23, 43 and 44 were carried over impurities from 23, 35 and 39.

Table-5.8

OH

O

OH

23 43

O

O

OH

N

10

OH

O

OH

44

O

O

OH

N

Preparation Of Glycopyrrolate: The compound of Formula 8 was further quarternized to its

bromide salt using methyl bromide, a class 3 solvent, to yield Glycopyrrolate having majority of

(S,R and R,S) diastereoisomer. The compound of Formula 8 a was dissolved in isopropyl

alcohol and treated with a solution of methyl bromide. After completion of the reaction, the

reaction mass was stirred to complete the crystallization. The precipitated product was filtered

and washed with isopropyl alcohol and dried under reduced pressure to obtain

Glycopyrrolidinium bromide.

In prior art procedures the quarternization of compound 8, usually takes about nine days.

However, in the present process of the invention quarternization was usually completed in 4-5

hrs. The crude methyl bromide quarternary salt was further purified by dissolving in methanol at



Chapter - V

60°C. To this hot solution, methyl ethyl ketone was slowly added and the reaction temperature

was cooled to 30°C and stirred for 3 hrs to complete crystallization. Filtration and drying

yielded the pure product.

This quaternisation reaction does not involve any complexity and proceeds smoothly.

Desmethyl Glycopyrrolate input with the requisite impurity profile was required to obtain

Glycopyrrolate having more than 99.5% purity. In this process, phenyl glyoxylic acid (11),

mandelic acid (23), methyl phenyl glyoxylate (16) and Glycopyrrolate hydroxy ester (6), having

no basic amino group in their structure, would not quarternies and would remain in mother

liquor. While Desmethyl Glycopyrrolate (8), we were controlling in reaction monitoring by

limiting this 0.5% by HPLC.

It was observed that Alkene Glycopyrrolate 45; formed in this step (from alkene desmethyl

Glycopyrrolate, 41) does not eliminate in mother liquor therefore we were controlling this, in

previous step by hydrogenation of this impurity and to convert back into Desmethyl

Glycopyrrolate 8.

Glycopyrrolate after isolation having 5-10% unwanted diastereoisomers (R,R and S,S), was

subjected to purification on using methanol and ethyl methyl ketone to brought it ≤ 1% by

HPLC and Chromatographic purity 99.5%.

CONCLUSION:

Hence, we have developed a 4-step preparation process for Glycopyrrolate, having process

control via Barbier reaction for the preparation of 6, hydrolysis, esterification, trans-

esterification and finally quaternization of amine for the large scale synthesis of Glycopyrrolate.

Present work detailed the journey towards development of a simple, safe, productive, eco-

friendly and easy to handle commercial process for preparing Glycopyrrolate. Hence, we have

developed and optimized the process, impurities formed in the process were identified, prepared

and characterized. Additionally, force degradation study of Glycopyrrolate was also



Chapter - V

investigated. A mechanistic rationale for the formation of the various process impurities and

degradation products has been provided.

EXPERIMENTAL SECTION:

(2RS)-2-Cyclopentyl-2-hydroxy-2-phenylacetic acid (Glycopyrrolate hydroxy acid, 10)

Magnesium turnings (110g, 4.58 mol) were suspended in dry tetrahydrofuran (150 ml) under

nitrogen atmosphere and heated the contents to 35-40°C. Catalytic amount of iodine (~1 g) was

added followed by a portion of solution (30 ml) from a mixture of methyl phenyl glyoxylate, 16

(500g, 3.05 mol) and cyclopentylbromide, 12 (545 g, 3.67 mol) in dry tetrahydrofuran (2850

ml). After initiation, remaining quantity of reactants mixture was added at 35-40°C in 90 min.

Reaction was monitored by qualitative HPLC. After completion of reaction, reaction mass was

added slowly to chilled water and thereafter neutralized the reaction mass with acetic acid.

Product was extracted into toluene and then concentrated. The concentrated mass thus obtained

was dissolved in methanol (500 ml) and 15% w/w aqueous sodium hydroxide solution (1000

ml) was added to it. Reaction mass was stirred at 20-25°C and monitored by qualitative HPLC

analysis. After completion of reaction, reaction mass was diluted with DM water (3000 ml) and

washed with toluene. Thereafter, pH of the aqueous layer was adjusted to 1.8 to 2.2 with

concentrated hydrochloric acid at 20-30°C to precipitate the product. The product was filtered

and washed with DM water. Filtered product (wet) was added to acetonitrile (850 ml) and

heated to 70-75°C to obtain a clear solution. DM water (3000 ml) was added to the above

solution at 70-75°C. Reaction mass was cooled slowly to 20-25°C and stirred for 2 hrs. Product

was filtered and washed with DM water (2x500 ml) and dried at 60-65°C under reduced

pressure (~20mm Hg) till water content was < 0.5% w/w (by KF). Yield: 260 g.;

Chromatographic purity: 95.68%.; water content: 0.24% w/w by KF titration.; Melting range:

135-142°C. Molecular Formula: C13H16O3; Molecular Weight: 220; Mass (ESI, in -ve ion

mode): 219.3 [(MH)-]; IR (KBr, cm

-1): 3418, 3060, 2958, 2872, 2631, 1721, 1600, 1489, 1451,

1364, 1328, 1312, 1297, 1234, 1199, 1186, 1168, 1116, 1080, 1028, 1000, 967, 926, 889, 760.



Chapter - V

1HNMR (DMSO-d6, 300 MHz, δ ppm): 1.16-1.58 (m, 8H, 4CH2); 2.82 (m, 1H, CH); 5.30 (brs,

1H, OH); 7.20-7.61 (m, 5H, Ar-H); 12.90 (brs, 1H, COOH).

Methyl (2RS)-2-Cyclopentyl-2-hydroxy-2-phenylacetate (Glycopyrrolate hydroxy ester, 6)

Glycopyrrolate hydroxy acid, 10 (200g, 0.91 mole) was suspended in toluene (1000 ml) and

added hydrogen chloride solution in methanol (500 ml, 18-22% w/w) at 20-25°C. Thereafter,

reaction mass was heated to 55°C and stirred at 55-60°C and monitored by qualitative HPLC

analysis. After completion of reaction, reaction mass was cooled to 20-25°C and transferred

slowly into chilled water. Product was extracted into toluene (2x600m1) and washed with 5%

w/w aqueous sodium bicarbonate solution (1x400m1) followed by DM water (400 ml) at 20-

25°C. The washed toluene layer was concentrated at 50-65°C under reduced pressure varying

from 200 mm to 20 mm of Hg to obtain the title compound as pale brown colour liquid. Yield:

204 g.; Chromatographic purity: 96.45 %.; Molecular Formula: C14H18O3; Molecular Weight:

234; Mass (ESI, in +ve ion mode): 235.3 [(MH)+]; IR (neat, cm

-1): 3515, 3090, 3061, 3026,

2954, 2869, 1956, 1892, 1727, 1600, 1496, 1448, 1436, 1368, 1316, 1255, 1194, 1173, 1106,

1072, 1035, 979, 952, 872, 847, 732. 1HNMR (DMSO-d6, 300 MHz, δ ppm): 1.15-1.57 (m, 8H,

4CH2); 2.82 (m, 1H, CH); 3.62 (s, 3H, CH3); 5.71 (s, 1H, OH); 7.18-7.57 (m, 5H, Ar-H).

(3RS)-3-[(2RS)-(2-Cyclopenty1-2-hydroxy-2-phenylacetyl)oxy]-1-methylpyrrolidine

(Desmethyl glycopyrrolate, 8)

Glycopyrrolate hydroxy ester, 6 (185g, 0.79mo1) and 1-methyl-3-pyrrolidinol, 7 (103.80g, 1.02

mole) were added to n-heptane (3000m1). Subsequently, ~1000m1 of n-heptane was removed

by distillation at atmospheric pressure to remove traces of moisture. After cooling to 30-35°C,

sodium methoxide (6.50g, 0.12mol) was added under nitrogen atmosphere and then heated the

contents to boiling while distilling out the azeotrope. The amount of solvent distilling out was

replaced by simultaneous addition of n-heptane to maintain the volume of the reaction mass and

monitored trans-esterification by qualitative HPLC. After completion of reaction, reaction mass

was cooled to 10-15°C and ~10% w/w aqueous hydrochloric acid solution (370m1) was added

to it. Reaction mass was washed with toluene (2 X 350m1). Toluene (750m1) was added to



Chapter - V

washed aqueous layer and pH was adjusted to 9.0-9.2 at 15- 20°C, with aqueous ammonia

solution. Product was extracted into toluene and the combined toluene extracts were washed

with DM water, and concentrated at 40-50°C under reduced pressure varying from 200mm to

20mm of Hg to get title product. Yield: 166.5g; Chromatographic purity: 95.89%; Assay (%

w/w, by titrimetry): 96.41.

Desmethyl glycopyrrolate, 8 (165g, 0.54mole) having alkene desmethyl glycopyrrolate, 41 was

dissolved in methanol (1000m1) and hydrogenated using palladium on carbon (8.0g) at 20-

30°C/ 40-60 psi. After completion, catalyst was removed by filtration and filtrate was

concentrated under reduced pressure to get the title compound as brown colour viscous liquid.

Yield: 164g; Chromatographic purity: 97.35%; Assay (% w/w, by titrimetry): 98.0. Molecular

Formula: C18H25NO3; Molecular Weight: 303; Mass (ESI, in +ve ion mode): 303.9 [(MH)+]; IR

(neat, cm-1

): 3512, 3089, 3061, 3025, 2951, 2867, 2788, 2697, 1728, 1600, 1495, 1478, 1448,

1421, 1376, 1329, 1250, 1192, 1173, 1122, 1088, 1072, 1037, 988, 973, 940, 886, 863, 731.

1HNMR (DMSO-d6, 300 MHz, δ ppm): 1.14-1.56 (m, 8H, 4CH2); 1.56 & 1.95 (2m, 2H, CH2);

2.19 (d, 3H, CH3); 2.26 (m, 1H, CH); 2.41 & 2.59 (2m, 2H, CH2); 2.61 & 2.84 (2m, 2H, CH2);

5.04 (m, 1H, CH); 5.61 (s, 1H, OH); 7.14-7.58 (m, 5H, Ar-H).

(3RS)-3-1(2RS)-(2-Cyclopentyl-2-hydroxy-2-phenyincetyl)oxy]-1,1-dimethylpyrrolidinium

bromide (glycopyrrolate, 1)

A solution of Desmethyl glycopyrrolate, 8 (150g, 0.49mole) in isopropyl alcohol (750m1) was

treated with a solution of methyl bromide in t-butyl methyl ether (25% w/w, 470g) at 25- 30°C.

After completion of reaction (monitored by HPLC), the reaction mass was stirred for 4h to

complete the crystallization. The product was filtered under nitrogen atmosphere and washed

with isopropyl alcohol (2x75m1). Thereafter, the product was dried at 40-50°C, under reduced

pressure (-20mm Hg). Yield: 78g; Chromatographic purity: 99.61%; Glycopyrrolate

diastereoisomer content: 9.03%.



Chapter - V

Purification

Glycopyrrolate crude (75g,) was heated in methanol (60 ml) at 50-60°C to obtain a clear

solution. Ethyl methylketone (750 m1) was added slowly maintaining temperature between 50-

60°C. Thereafter, the contents were cooled slowly to 25-30°C and stirred for 3h to complete the

crystallization. The product was filtered and washed with ethyl methylketone (2x75 m1).

Finally the product was dried to constant weight at 50-55°C under reduced pressure (-20mm

Hg). Yield: 60g; Chromatographic purity: 99.92%; Glycopyrrolate diastereoisomer content:

0.27%. Molecular Formula: C19H28BrNO3; Molecular Weight: 398.34; Mass (ESI, in +ve ion

mode): 317.9 [(M-Br)+]; IR (KBr, cm

-1): 3334, 3065, 3051, 3033, 3001, 2989, 2963, 2912,

2870, 1740, 1698, 1598, 1481, 1446, 1372, 1333, 1298, 1284, 1271, 1229, 1197, 1182, 1168,

1140, 1119, 1109, 1094, 1076, 1068, 1032, 956, 942, 918. 1HNMR (DMSO-d6, 300 MHz, δ

ppm): 1.18-1.59 (m, 8H, 4CH2); 2.05 & 2.70 (2m, 2H, CH2); 2.91 (m, 1H, CH); 3.10 & 3.18 (2s,

6H, 2CH3); 3.52 & 3.71 (2m, 2H, CH2); 3.66 & 3.87 (2m, 2H, CH2); 5.37 (brs, 1H, CH); 5.83 (s,

1H, OH); 7.24-7.60 (m, 5H, Ar-H). 13

C NMR(DMSO-d6) (proton decoupled) in δppm: 26.5,

26.9, 26.9, 27.5, 30.5, 47.5, 52.8, 53.4, 64.7, 70.0, 73.6, 80.1, 126.5, 128.1, 128.8, 143.0, 174.3.

SYNTHESIS OF 11:

A solution of methyl phenyl glyoxalate, 16 (30g, 0.18 mole) in methanol (120 m1) was treated

with a solution of 4N sodium hydroxide (60 ml) at 25-30°C for 2h followed by 1h maintenance

at 50°C. After completion of reaction (monitored by HPLC), the reaction mass was concentrated

at 45-50°C under reduced pressure. Reaction mass was acidified with 3N hydrochloric acid

solution (~70 ml) and product was extracted in methylene chloride (3x100 ml). This was

concentrated under reduced pressure and obtained gummy mass was stirred with cyclohexane

(100 ml). Stirred for 2h to complete the crystallization, obtained product was filtered and

washed with cyclohexane (2x20 m1). Thereafter, the product was dried at 40-50°C, under

reduced pressure (-20mm Hg) to get off-white crystalline powder. Yield: 22.10g;

Chromatographic purity: 99.58%. Molecular Formula: C8H6O3; Molecular Weight: 150; Mass



Chapter - V

(ESI, in -ve ion mode): 149.0 [(M-H)-]; IR (KBr, cm

-1): 3675, 3647, 3356, 3066, 2558, 2346,

1971, 1736, 1686, 1597, 1579, 1561, 1494, 1452, 1398, 1318, 1217, 1180, 1101, 1002, 980,

939, 739. 1HNMR (DMSO-d6, 300 MHz, δ ppm): 7.56 (dd, 2H, Ar-H); 7.69 (dd, 1H, Ar-H);

7.90 (d, 2H, Ar-H).

SYNTHESIS OF 16:

This is the key raw material, we have procured from outside. A clear pale yellow liquid.

Molecular Formula: C9H8O3; Molecular Weight: 164; Mass (GC-MS(QP-5050A))-EI : 164; IR

(neat, cm-1

): 3357, 3160, 3066, 3033, 3008, 2956, 2901, 2847, 1916, 1736, 1719, 1690, 1648,

1596, 1579, 1560, 1538, 1491, 1451, 1437, 1398, 1367, 1325, 1208, 1175, 1005, 939, 911, 847.

1HNMR (DMSO-d6, 300 MHz, δ ppm): 3.96 (s, 3H, OCH3); 7.61-7.66 (dd, 2H, Ar-H); 7.77-

7.83 (dd, 1H, Ar-H); 7.98 (d, 2H, Ar-H).

SYNTHESIS OF 18:

Magnesium turnings (9.09 g, 0.38 mol) were suspended in dry tetrahydrofuran (20 ml) under

nitrogen atmosphere and heated the contents to 60-62°C. Catalytic amount of iodine (~0.1 g)

was added followed by 3-5 drops of cyclopentyl bromide, 12. After initiation of reaction, added

remaining quantity of 12 (37.61 g, 0.25 mol) diluted with THF (250 ml) at such a rate that

temperature maintained between 55-60°C during addition. After completion of reaction,

reaction mass was heated to reflux for further 1h. Thereafter, reaction mass was cooled to 25-

30°C and benzonitrile (20 g, 0.19 mol) diluted with THF (50 ml) was added and refluxed for 2h.

After completion of reaction, reaction mass was added slowly to chilled water and thereafter

neutralized the reaction mass with acetic acid. Reaction mass was concentrated to remove THF

under reduced pressure, concentrated mass thus obtained was dissolved in toluene (100 ml) and

basified with aqueous ammonia solution to pH 9.5. Toluene layer was separated and product

was extracted in toluene (2x100 ml). This was concentrated under reduced pressure and

obtained oily mass was distilled at 2-0.5 mmHg and collected different fractions. Yield: 10.28

g.; Chromatographic purity: 95.68%. Molecular Formula: C12H14O; Molecular Weight: 174;



Chapter - V

Mass (ESI, in +ve ion mode): 174.3 [(MH)+];

1HNMR (DMSO-d6, 300 MHz, δ ppm): 1.58-1.90

(m, 8H, 4CH2); 3.80 & 3.86 (m, 1H, CH); 7.50-7.99 (m, 5H, Ar-H).

SYNTHESIS OF 21:

Benzyl cyanide (20g, 0.17 mole) was added in dry THF (200 ml) under nitrogen atmosphere

and cooled to -30 to -35°C. After addition of n-BuLi (117 ml, 0.19 mol) at -35±5°C, reaction

mass was further cooled to -65±5°C and stirred for 15 min. Cyclopentyl bromide (24.47 g, 0.17

mol) diluted in THF (50 ml) was added in 2h duration at -65±5°C and stirred for 1h. After

completion of reaction, raised temperature to 25°C and added methanol:THF (1:1, 50 ml)

followed by DM water (50 ml). Organic layer was separated and extracted product in methylene

chloride (2x50 ml). Combined organic layer was dried on sodium sulphate and concentrated

under reduced pressure. Obtained crude product was distilled to collect different boiling

fractions, and the fraction distilling at 120-125°C/~1 mmHg was collected as pure α-cyclopentyl

phenyl acetonitrile (20 g).

50% w/w aqueous sodium hydroxide solution was added to obtained pure fraction of α-

cyclopentyl phenyl acetonitrile and heated to reflux for 20h. Extracted unreacted compound in

methylene chloride, diluted aqueous layer with DM water, acidified and maintained stirring for

15h. Obtained crystalline product was filtered, washed with DM water and dried under reduced

pressure. Molecular Formula: C13H16O2; Molecular Weight: 204.26; Mass (ESI, in -ve ion

mode): 203.3 [(M-H)-];

1HNMR (DMSO-d6, 300 MHz, δ ppm): 0.99-1.94 (m, 8H, 4CH2); 2.56

(m, 1H, CH); 3.27 (d, 1H, CH); 7.23-7.35 (m, 5H, Ar-H).

SYNTHESIS OF 23:

This is (±)-mandelic acid, we have procured from outside. Molecular Formula: C8H8O3;

Molecular Weight: 152; Mass (ESI, in -ve ion mode): 151.1 [(M-H)-]; IR (neat, cm

-1): 3449,

3066, 3037, 2909, 2659, 1725, 1496, 1456, 1308, 1287, 1248, 1193, 1097, 1080, 1064, 1026,

933, 863. 1HNMR (DMSO-d6, 300 MHz, δ ppm): 5.03 (s, 1H, CH); 5.85 (brs, 1H, OH); 7.25-

7.43 (m, 5H, Ar-H); 12.59 (brs, 1H, CO2H).



Chapter - V

SYNTHESIS OF 33:

Magnesium turnings (22g, 0.91 mol) were suspended in dry tetrahydrofuran (50 ml) under

nitrogen atmosphere and heated the contents to 35-40°C. Catalytic amount of iodine (~0.3 g)

was added followed by a portion of solution (10 ml) from a mixture of methyl phenyl

glyoxylate, 16 (100g, 0.61 mol) and 3-bromocyclopentene (107.6 g, 0.73 mol) in dry

tetrahydrofuran (450 ml). After initiation, remaining quantity of reactants mixture was added at

35-40°C in 90 min. Reaction was monitored by qualitative HPLC. After completion of reaction,

reaction mass was added slowly to chilled water and thereafter neutralized the reaction mass

with acetic acid. Product was extracted into toluene and then concentrated. The concentrated

mass thus obtained was dissolved in methanol (100 ml) and 15% w/w aqueous sodium

hydroxide solution (250 ml) was added to it. Reaction mass was stirred at 20-25°C and

monitored by qualitative HPLC analysis. After completion of reaction, reaction mass was

diluted with DM water (600 ml) and washed with toluene. Thereafter, pH of the aqueous layer

was adjusted to 0.6 with concentrated hydrochloric acid at 20-30°C to precipitate the product.

No crystallization occurred. Extracted product in toluene (1x300 ml, 1x100 ml) at 25-30°C and

was concentrated at 50-60°C under reduced pressure varying from 200 mm to 20 mm of Hg to

obtain the title compound 33 as pale brown colour liquid. Water content : 0.26% w/w (by KF).

Yield: 61.5 g.; Chromatographic purity: 88.32%.; Molecular Formula: C13H14O3; Molecular

Weight: 218; Mass (ESI, in -ve ion mode): 217.1 [(M-H)-];

1HNMR (DMSO-d6, 300 MHz, δ

ppm): 1.48 (m, 1H, CH2); 1.88 (2m, 1H, CH2); 2.20 (m, 2H, CH2); 3.67 (m, 1H, CH); 5.11 &

5.55 (dd, 1H, CH); 5.62 & 5.85 (dd, 1H, CH); 7.38 (m, 2H, Ar-H); 7.64 (m, 2H, Ar-H); 7.94 (m,

1H, Ar-H); 12.90 (brs, 1H, COOH).

SYNTHESIS OF 37:

33 (60g, 0.28 mole) was suspended in toluene (300 ml) and added hydrogen chloride solution in

methanol (150 ml, 18-22% w/w) at 20-25°C. Thereafter, reaction mass was heated to 55°C and

stirred at 55-60°C and monitored by qualitative HPLC analysis. After completion of reaction,

reaction mass was cooled to 20-25°C and transferred slowly into chilled water. Product was



Chapter - V

extracted into toluene (3x180m1) and washed with 5% w/w aqueous sodium bicarbonate

solution (1x60m1) followed by DM water (60 ml) at 20-25°C. The washed toluene layer was

concentrated at 50-65°C under reduced pressure varying from 200 mm to 20 mm of Hg to

obtain the title compound 37 as pale brown colour liquid. Yield: 62.7 g.; Chromatographic

purity: 58.42 %.; Molecular Formula: C14H16O3; Molecular Weight: 232; Mass (ESI, in +ve ion

mode): 233.2 [(MH)+];

1HNMR (DMSO-d6, 300 MHz, δ ppm): 1.48 (m, 1H, CH2); 1.88 (2m,

1H, CH2); 2.19 (m, 2H, CH2); 3.14 (s, 1H, CH); 3.63 (s, 3H, CH3); 5.11 & 5.55 (dd, 1H, CH);

5.62 & 5.82 (dd, 1H, CH); 5.56 &5.73 (s, 1H, OH); 7.38 (m, 2H, Ar-H); 7.64 (m, 2H, Ar-H);

7.94 (m, 1H, Ar-H)

SYNTHESIS OF 41:

37 (60g, 0.26 mo1) and 1-methyl-3-pyrrolidinol, 7 (34g, 0.34 mole) were added to n-heptane

(1600m1). Subsequently, ~1000m1 of n-heptane was removed by distillation at atmospheric

pressure to remove traces of moisture. After cooling to 30-35°C, sodium methoxide (2.25g,

0.08mol) was added under nitrogen atmosphere and then heated the contents to boiling while

distilling out the azeotrope. The amount of solvent distilling out was replaced by simultaneous

addition of n-heptane to maintain the volume of the reaction mass and monitored trans-

esterification by qualitative HPLC. After completion of reaction, reaction mass was cooled to

10-15°C and ~10% w/w aqueous hydrochloric acid solution (120m1) was added to it. Reaction

mass was washed with toluene (2 X 120m1). Toluene (240m1) was added to washed aqueous

layer and pH was adjusted to 9.0-9.2 at 15- 20°C, with aqueous ammonia solution. Product was

extracted into toluene and the combined toluene extracts were washed with DM water, and

concentrated under reduced pressure to get the title compound 41 as brown colour viscous

liquid. Yield: 40g; Chromatographic purity: 97.96%; Molecular Formula: C18H23NO3;

Molecular Weight: 301; Mass (ESI, in +ve ion mode): 302.1 [(MH)+]; IR (neat, cm

-1): 3059,

2946, 2847, 2790, 1732, 1601, 1479, 1449, 1354, 1238, 1164, 1114, 1072, 1036, 895, 742, 701.

1HNMR (DMSO-d6, 300 MHz, δ ppm): 1.42-1.68 (2m, 2H, CH2); 1.71-1.89 (2m, 2H, CH2);



Chapter - V

2.14 & 2.65 (2m, 4H, 2CH2); 2.22 (m, 3H, CH3); 2.51 (m, 2H, CH2); 3.61 (m, 1H, CH); 5.04 (m,

1H, CH); 5.06 & 5.45 (2m, 1H, CH); 5.63 & 5.81 (2m, 1H, CH); 7.29-7.58 (m, 5H, Ar-H).

SYNTHESIS OF 45:

A solution of 41 (10g, 0.03mole) in acetone (100m1) was treated with a solution of methyl

bromide in t-butyl methyl ether (25% w/w, 37g, 0.08mole) at 25- 30°C. After completion of

reaction (monitored by HPLC), the reaction mass was concentrated under reduced pressure at

45-50°C. Methyl ethyl ketone (200 ml ) was added the title compound was stirred for 4h to

complete the crystallization. The product was filtered under nitrogen atmosphere and washed

with Methyl ethyl ketone (2x10m1). Thereafter, the product was dried at 40-50°C, under

reduced pressure (~20mm Hg). Yield: 6g; Chromatographic purity: 29.88 & 57.49% at 0.58 &

0.62 RRT. Molecular Formula: C19H26BrNO3; Molecular Weight: 396.34; Mass (ESI, in +ve

ion mode): 316.1 [(M-Br)+];

1HNMR (DMSO-d6, 300 MHz, δ ppm): 1.75-1.91 (2m, 2H, CH2);

2.24-2.27 (m, 2H, CH2); 2.14 & 2.65 (2m, 2H, CH2); 3.09-3.18 (2m, 6H, 2CH3); 3.51 (m, 1H,

CH); 3.54 & 3.68 (m, 2H, CH2); 3.63 & 3.82 (2m, 2H, CH2); 5.15 (m, 1H, CH); 5.39 (m, 1H,

CH); 5.72 (dd, 1H, CH); 7.29-7.58 (m, 5H, Ar-H).

SYNTHESIS OF 47:

This impurity was isolated from preparative HPLC. Molecular Formula: C24H36NO3; Molecular

Weight: 386.27; Mass (ESI, in +ve ion mode): 386.3 [(M)+];

1HNMR (DMSO-d6, 300 MHz, δ

ppm): 1.21-1.76 (m, 16H, 8CH2); 2.05 & 2.70 (2m, 2H, CH2); 2.91 (m, 2H, CH); 3.08 & 3.15

(2s, 6H, 2CH3); 3.52 & 3.71 (2m, 2H, CH2); 3.66 & 3.87 (2m, 2H, CH2); 5.34 (brs, 1H, CH);

7.12-7.60 (m, 5H, Ar-H).



Chapter - V

SPECTRA:

…..IR, 1H NMR AND MASS SPECTRUM OF COMPOUND 10



Chapter - V




Chapter - V

…..IR, 1H NMR,

13C NMR AND MASS SPECTRUM OF COMPOUND 1



Chapter - V




Chapter - V

…..1H NMR AND MASS SPECTRUM OF COMPOUND 16

…..1H NMR SPECTRUM OF COMPOUND 18



Chapter - V

…..MASS SPECTRUM OF COMPOUND 18




Chapter - V




Chapter - V

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Studies on the synthesis of anti-cholinergic drug...

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