Modern Methods for the Separation of Enantiomers - from...

Organic Process Research and Development

February 2014

Modern Methods for the

Separation of Enantiomers

- from Kilos to Tons -

- Over 80% of drug candidates contain at least one chiral center

- Increasingly complex molecules, requiring more advanced production methodologies -Three General Strategies -Chiral Pool -Asymmetric Synthesis -Resolution

Chirality in Drug Pipeline

• Is there an optimal approach to problem?

• No – each stage is driven by different imperatives, therefore choices are also different

Challenge

• Short-term Focus

–Speed is key

–Cost less of an issue

• Pragmatic approach

–Produce racemate then separate

–Less effort on asymmetric synthesis, chiral pool (only if quick and easy)

Pre-Clinical

• Long-term focused

– Scalability, cost, efficiency, robustness

• “Tool Box” Approach

– Cannot assume that any approach is invalid

– Test all, then run economic feasibility

Clinical

• Used at all stages

– Classical Resolution

– Chiral Chromatography

• Enabling Chiral Separations

– Developing efficient methods

– Small-scale runs (> 100kg)

– Technology Transfer for commercial

Chiral Separation

CHIRAL TECHNOLOGIES INC.

West Chester, PA.

23,000 sq ft Labs &

Offices

• Chromatography is considered to be:

– Last Resort

– Temporary Solution

– Inelegant

– Difficult to Use

Perceptions of Chromatography

• Chromatography is;

– Cost effective

– Reliable

– Scalable

Reality of Modern Chromatography

Scalable Technology

Photo courtesy of AMPAC

Methods are developed on analytical columns

Scalable Technology

Photo courtesy of AMPAC

Ampac Fine Chemicals

• Screen compound

– Chiral Stationary Phase (CSP)

– Mobile Phase

• Determine Optimum Combination

• Perform Loading Study

• Run Stability Tests

• Productivity = kg enantiomer/kg CSP/day

Chiral Chromatography Method Development

• Solubility characteristics

• Stability (chemical and stereo)

• Presence of other impurities

• API or intermediate

• Ability to racemize non-target enantiomer

Key Points to Consider

Chiral Stationary Phase

RO

O

OR

ORO n RO

O

OR

OR

O

n

Amylose-based Cellulose-based

-R Nature CSP -R Nature CSP

Immobilized CHIRALPAK IA

Immobilized CHIRALPAK IB

Immobilized CHIRALPAK IC

NH

O CH3

CH3

NH

O CH3

CH3

NH

O Cl

Cl

CHIRALPAK ID Immobilized NH

O Cl

Immobilized CHIRALPAK IE NH

O Cl

Cl

Screening Study a-Methyl-a-Phenylsuccinimide

EtOAc

THF/Hexane

MTBE

min 0 5 10 15 20 25 30 35

mAU

0

20

40

60

80

100

120

NH

OO

Multiple separation opportunities

Also separates with conventional

solvents. Note, zero THF

selectivity

CHCl3

ACN:IPA 85:15

CHIRALPAK IA, 250 x 4.6 mm

Flow rate 1 ml/min

UV detection 254 nm

3.9

8.3

0 1 2 3 4 5 6 7 8 9 10

Retention Time (min)

0.0

0.1

0.2

0.3

0.4

0.5

Absorbance (AU)

Analytical injection

Dichloromethane/THF 70:30 F = 1 mL/min, 25°C

(Column 25 x 0.46 cm, 5 µm CSP)

Solubility in mobile phase: 45 g/L

Chiral Separation of EMD-53986

N H

N

N H

O

S

EMD-53986

Precursor for Ca-sensitizing drug

3.9

8.3

0 1 2 3 4 5 6 7 8 9 10


0.0

0.1

0.2

0.3

0.4

0.5

Absorbance (AU)

loading

16mg

20mg

4mg

8mg

12mg




Loading Study for EMD-53986

3.9

8.3

0 1 2 3 4 5 6 7 8 9 10


0.0

0.1

0.2

0.3

0.4

0.5

Absorbance (AU)

loading

16mg

20mg

4mg

8mg

12mg



Estimated productivity:

2.8kg enantiomer/kg CSP/day


Loading Study for EMD-53986

Preparative chromatography

HPLC (batch) SMB (continuous)

Glutethimide

Productivity: > 11 kg enantiomer/kg CSP/day

0 1 2 3 4 5 6 7 8

min

9 10 11

54 mg

42 mg

36 mg

30 mg

15 mg

Ethyl acetate 100% F = 1 mL/min, 25°C



Productivity demonstrated

under SMB conditions

• Two Clinical Development Projects

1) Continuous Enantio-Enrichment

2) Stage-Appropriate Technology

Case Studies

• Biogen Idec Alzheimer’s Drug

- BIIB042

- Two chiral centers

- Continuous process developed

1) Continuous Enantio-Enrichment

BIIB042 Structure

*

*

OH

BIM-651

N

F

OH

N

F

OTf

N

F

CF3

BIO-20377

N

F

CF3

Chiralseparation

+NH CHO

F

+

Mannich Triflation

Suzuki Hydrolysis

N

F

CF3

BIIB042

90%

60-80% 100%15-18%

70-80%

MeO

O MeO

O

MeO

O

MeO

O

HO

O

OH

O

BIM 702

Initial Drug Discovery Approach

The Mannich reaction established the framework for BIIB042 in the first step producing BIM-702, and chiral chromatography was employed to separate the four stereoisomers.

toluene, 110 oCOH

N

CO2Me

F

BIM-702

OH

CO2Me

NH

OHC

F

+

*

RX Heptane 70-75%

diastereomeric salts andenzymatic approacheswere not successful

SMB, 100%

OH

N

CO2Me

F

BIM-752

Formation of First Chiral Center

• Screened against matrix of chiral stationary phases/solvents

- Best method; AD CSP with Hexane/IPA

• Determined optimum process parameters

- Yield, %ee

Chiral SMB Approach

Continuous SMB Process

Racemic BIM702

Chiral SMB

90 kg


Racemic BIM702

Chiral SMB

BIM752

>99.5%ee

90 kg


Racemic BIM702

Chiral SMB

BIM752 Non-Target Enantiomer

>99.5%ee

90 kg


Racemic BIM702

Chiral SMB

BIM752 Non-Target Enantiomer

Racemization

>99.5%ee

90 kg

Lab Scale SMB

Second Chiral Center

>95% ee via catalytic hydrogenation (Ru)

N

C O 2 H

C F 3

F

R u ( B I N A P ) , H 2

4 0 a t m e n a n t i o s e l e c t i v e

*

* N

C O 2 M e

F

B I M - 7 5 7

C F 3

N

C O 2 H

F

B I M - 7 9 5

*

C F 3

B I I B 0 4 2

S o d i u m t r i m e t h y l s i l o n a t e

*

• Development of Armodafinil

• Cephalon (Teva)

2) Stage-Appropriate Technology

S

O O

NH2

Stage-Appropriate Technology

• Modafinil (Provigil)

– Approved for treatment of apnea, narcolepsy, shift work disorder

– Racemic API

• Armodafinil (Nuvigil)

– (R)-Enantiomer

– Second generation therapy

S

O O

NH2

Pre-Clinical Phase

aq. NaOH

aq. HCl, acetone

Na2CO3, Me2SO4

aq. acetone

NH3, MeOH

DMSAM Modafinil Modafinic Acid

- Modafinic Acid was the best candidate for classical resolution

- Easily converted to R-Modafinil

• 85 kgs prepared via crystallization

- ~98% ee

- Conversion to R-Modafinil

- Non-ideal system due to

● Product degradation

● Cost inputs

● High labor component

Pre-Clinical Phase

S

O O

NH2

Clinical Phase

• Chiral HPLC/SMB study on Modafinil

– Screened CSPs

– HPLC and SMB methods developed

• 60kg of Phase I material produced

– Single column HPLC

– >99.0%ee

S

O O

NH2HPLC

• 550kg Phase II/III material produced - Chiral SMB

- Optical purity >99.2%

- Chemical purity >99.7%

• Over 10 MT of racemate processed via SMB - Novasep operation

- Process ran on 300mm and 450mm systems

- Stabile, robust process

Clinical Phase

• Asymmetric Oxidation Results

- 75% isolated yield

- >99.5% optical purity

• Significantly longer development than chromatography

• Favorable economics

• Launch of Armodafinil was accelerated due to stage-appropriate technologies

Commercial Launch

• Three different methods employed

• Pre-Clinical – Classical Resolution

• Clinical Trials – Chiral SMB

• Commercial Launch – Asymmetric Synthesis

• Result – Speed to Market

Development of Armodafinil

• Chiral Chromatography can offer advantages

– Effective from mgs to MTs

– Predictable scale factors

– Ability to “dial in” desired %ee

Conclusions

• Biogen Idec

• Teva (Cephalon)

• Novasep

Acknowledgements Thank You Partners

Chiral Technologies

48

Modern Methods for the Separation of Enantiomers - from...

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