New Strigolactone Analogues, Design, Synthesis and … · 11th WCPP, June 7-12 , 2011 1 Radboud...
Transcript of New Strigolactone Analogues, Design, Synthesis and … · 11th WCPP, June 7-12 , 2011 1 Radboud...
11th WCPP, June 7-12 , 2011 1
Radboud University Nijmegen Department of Organic Chemistry
New New StrigolactoneStrigolactone Analogues, Design, Synthesis Analogues, Design, Synthesis
and Bioactivityand Bioactivity
Binne Zwanenburg,
Heetika Malik, A.Simon Mwakaboko and Floris P.J.T. Rutjes
Radboud University Nijmegen
The Netherlands
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Radboud University Nijmegen Department of Organic Chemistry
Parasitic Weeds:Parasitic Weeds:
Beautiful flowers but a real pestBeautiful flowers but a real pest
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Radboud University Nijmegen Department of Organic Chemistry
StrigaStriga seed germinationseed germination
Seed germinationGermination test of stimulants
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Radboud University Nijmegen Department of Organic Chemistry
Interaction between host and parasitic weedInteraction between host and parasitic weed
simplified schemesimplified scheme
Hostreleases Chemical signal =
germination stimulant
interaction
Seeds of the parasiteAttachment on
host roots
detrimental effect
induction of
germination
Occurrence of Striga spp: tropical and subtropical areas in Africa and Azia (India).
Food crops: maize, sorghum, millet and rice; yield losses 50-90%; 100 million African people suffer.
Occurrence of Orobanche spp: mediterranean area, Eastern Europe and Middle East.
Food crops: legumes (tomato, fava beans), sunflower and tabacco; damage severe.
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Radboud University Nijmegen Department of Organic Chemistry
� isolated from cotton(Cook et al., 1966)
� absolute configuration (Brooks et al., 1985)
� isolated from maize (Siame et al., 1993)
� activity 10-7-10-12 M
� isolated from sorghum(Hauck et al., 1992)
� absolute configuration: confirmed by total synthesis (Zwanenburg et al., 1997)
� activity 10-9-10-12 M
� isolated from cowpea(Müller et al., 1992)
� exact structure: unknown� absolute configuration:
unknown� activity 10-12 M?
Strigol Sorgolactone Alectrol Orobanchol
� isolated from red clover(Yokota et al., 1999)
� absolute configuration:confirmed by total synthesis (Mori et al., 1999)
� activity
OOO
O O
OH
A B
D
C
OOO
O O
A B
D
C
OOO
O OOH
A B
D
C
OOO
O O
OH
A B
D
C
NaturallyNaturally occurringoccurring germinationgermination stimulantsstimulants
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Radboud University Nijmegen Department of Organic Chemistry
Tentative Molecular MechanismTentative Molecular Mechanism
Characteristics of the proposed mechanism:
� Addition/Elimination of nucleophilic site of the receptor
� Nucleophilic site e.g.: HS(-), H2N
(-)
� D-ring serves as a good leaving group
E.M. Mangnus, B. Zwanenburg; J.Agric.Food Chem., 1992, 40, 1066-1070.
OOO
O O
D
CNu
- O O
Nu
+-O
OO
OOO
O O
Nu
-
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Radboud University Nijmegen Department of Organic Chemistry
Relevant Structural FeaturesRelevant Structural Features
OOO
O O
A B
D
CR
*
*
*
Stereochemistry
is very important
A-ring modifications
don’t reduce activity
α,β-unsaturated systemand D-ring are essential
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Radboud University Nijmegen Department of Organic Chemistry
� Best chance for selectivity
� Best way to design active compounds, especially when the bioactiphore can be identified
� Low concentration (environmental issue)
� Best chance of decomposition in the soil (this is a prerequisite for the natural stimulant)
� Molecular fine tuning is based on a model
� No time consuming random search for a lead
Natural Stimulants as a lead for Weed Control,Natural Stimulants as a lead for Weed Control,
Why??Why??
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Radboud University Nijmegen Department of Organic Chemistry
NijmegenNijmegen--11
ED50: 10-7 M Striga hermonthica10-6 M Orobanche crenata
OOO
N
O
O
O
O
Nijmegen-1
Nefkens, G.H.L., Thuring, J.W.J.F., Beenakkers, M.F.M., Zwanenburg, B.
J. Agric. Food Chem., 1997, 45, 2273-2277.
Easy synthesis; potential candidate for use in suicidal germination
The essential features of the bioactiphore are connected to a simple scaffold, i.e. phthalimide
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Radboud University Nijmegen Department of Organic Chemistry
Field test Suicidal Germination, Field test Suicidal Germination, O. O. ramosaramosa
tobacco field treated with Nijmegen-1 untreated tobacco field
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Radboud University Nijmegen Department of Organic Chemistry
Relevant Structural Features, Model for Design of new Relevant Structural Features, Model for Design of new StrigolactonesStrigolactones
OOO
O O
A B
D
CR
*
*
*
Stereochemistry
is (very)
important
A-ring modifications
don’t reduce activity
α,β-unsaturated systemand D-ring are essential
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Radboud University Nijmegen Department of Organic Chemistry
Strategy: *Incorporate essential structural feature, using simplStrategy: *Incorporate essential structural feature, using simple e
scaffolds. *Obey the molecular mechanism. *Use simple scaffolds. *Obey the molecular mechanism. *Use simple
starting materials. *Dstarting materials. *D--ring must be presentring must be present
Two step synthesis, one pot.Two step synthesis, one pot.
New New StrigolactonesStrigolactones from simple from simple KetonesKetones
O OX
7, X = Cl
O O
OO O
B. HCO2Et, t -BuOK, THF;
7, DMF, sequential
10, n = 18, n = 19, n = 2
A. HCO2Me, Na, DMF, 7,sequential ( )n( )n
11, n = 2
halo butenolide
C. HCO2Me, t-BuOK; 7, t-BuOK, two steps
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Radboud University Nijmegen Department of Organic Chemistry
Bioassays of new Strigolactone Analogues from Ketones
0
20
40
60
80
100
indanone tetralone GR 24
% g
erm
ination
S. hermontica
0
20
40
60
80
100
indanone tetralone GR 24
% g
erm
ination
O.crenata1 ppm0.1 ppm0.01 ppm
O
O
O
O
Tetralone analogueAs good as GR 24!!
O
O
OO
Indanone analogue
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Radboud University Nijmegen Department of Organic Chemistry
New New StrigolactoneStrigolactone Analogues from simple Analogues from simple KetonesKetones
All are active as germination stimulants, best are those from carvone (30) and pulegone (31)
Mwakaboko, Zwanenburg, Plant & Cell Physiol. 52, 699-715 (2011)
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Radboud University Nijmegen Department of Organic Chemistry
New New StrigolactoneStrigolactone Analogues from Analogues from KetoKeto EnolsEnols in a single Stepin a single Step
O O
OH
14
15
O O
OO
O
K2CO3, DMF
OCl O
8
O
O
O
O
O
O
DMF, 8
K2CO3
RR R
R
R = H 16
R = Me 18R = H 17
R = Me 19
R=H; R=Me
OX= OH=start.mat.
activity: ** *** **** ****** ****
OX=
stimulantO
O
HO
OX
O
OOX O O
OX
O O
OX
O
OXRR
O OO
O
OX
*
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Radboud University Nijmegen Department of Organic Chemistry
O
O
O
O
from triacetic acid lactone
O
O
O
OO
from 4-hydroxy coumarin
O
O
O
O
from dimedone
Excellent performance for analogues from dimedoneand hydroxy coumarin
S. hermonthica 0.1 mg/L: 57% germination 0.01 mg/L: 63%
O. cernua 0.1 mg/L: 79% germination 0.1 mg/L: 80%
S. hermonthica 0.1 mg/L: 62% germination
O. cernua 0.1 mg/L: 76% germinationSubmitted for publication
New New StrigolactonesStrigolactones for Suicidal Germination derived from for Suicidal Germination derived from KetoKeto
EnolsEnols in a single Stepin a single Step
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Radboud University Nijmegen Department of Organic Chemistry
StrigolactoneStrigolactone Analogue derived from SaccharineAnalogue derived from Saccharine
S
N K
O
S
N
OO
SN
OO
HO
ClCH2COCH3 (i) HCO2CH3, Na
(ii) H+
SN
OO
O
O
O
KOBut
DMF, 10
DMF, RefluxO O O O O O
O O
12 1617
18
10 is chloro-butenolide
Highly active germination stimulant for
S. hermonthica and O. cernua at 0.1 mg/L
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Radboud University Nijmegen Department of Organic Chemistry
A major obstacle is the A major obstacle is the
preparation of the Dpreparation of the D--ring! The CHring! The CH33--
group is absolutely necessarygroup is absolutely necessary
See Synthesis, 2010, 3271See Synthesis, 2010, 3271--32733273
O O
COOHO
COOH
2) p-TsOH, benzene, ∆
1) NaBH4
O O
H2, Pd/Cglyoxylic acid
benzene / anisole, ∆
O O
O OO
OCl O
1) Na or KOtBU, ethyl formate
2)
, THF
GR 24
Synthesis of GR 24Synthesis of GR 24
Zwanenburg et al : J. Agr. Food Chem. 47, 1705-1710 (1999);idem 40, 1230-1235 (1992);
New synthesis of GR24:Tetrahedron
66, 7198-7203 (2010)
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Radboud University Nijmegen Department of Organic Chemistry
Synthesis of Aromatic Synthesis of Aromatic OrobancholOrobanchol, introduction of OH in B, introduction of OH in B--ringring
O O
+
O O O O
O O
i ii
O OH
OH
iii, iv
(3%)
82 %9a
9b
Reagents and conditions: (i) FeCl3 (2 mol %), aq tBuOOH (70%, 3 equiv)
pyridine, 82 ºC, 24 h, (ii) NaBH4, CeCl3.7H2O, EtOH, (iii) PPh3,
PhCO2H, EtO2CN=NCO2Et, toluene, (iv) K2CO3, MeOH.
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Radboud University Nijmegen Department of Organic Chemistry
Synthesis of Aromatic Synthesis of Aromatic OrobancholOrobanchol, introduction of D, introduction of D--ring, OH ring, OH
down, no protection neededdown, no protection needed
O
O
O
O O
+
O
O
O
O OOH OH
9b
11aαααα 11aββββ
O OBr
10
i
O
O
O
O O
+
O
O
O
O OOAc OAc
12aαααα ((((99995555%%%%)))) 12aββββ ((((99995555%%%%))))
ii
Reagents and conditions:
HCO2Me, t-BuOK, THF, then butenolide 10, DME (ii) Ac2O, pyridine, CH2Cl2.Malik, Kohlen, Jamil, Rutjes, Zwanenburg, Org. Biomol. Chem. 9, 2286-2293 (2011)
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Radboud University Nijmegen Department of Organic Chemistry
Aromatic Aromatic OrobancholOrobanchol, introduction D, introduction D--ring ,OH up, protection neededring ,OH up, protection needed
O
O
O
O O
+
O
O
O
O OOH OH
O O
iii
O
O
O
O O
9a
OMOM
16bαααα
13b: PG = MOM15b: PG = SEM
OPG
16bββββ
iv
v
O
O
O
O O
+
O
O
O
O OOAc OAc
17bαααα ((((99993333%%%%)))) 17bββββ ((((99994444%%%%))))
i or ii
14biii for15b
Reagents and conditions: (i) MOM chloride, DIPEA, CH2Cl2, rt, 16 h, (ii) DIPEA, SEMCl, CH2Cl2,
22 h, (iii) HCO2Me, t-BuOK, THF, then butenolide 10, DME, workup with 1 M HCl
(iv) ZnBr2, CH2Cl2, 25 °C, (v) Ac2O, pyridine, CH2Cl2.
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Radboud University Nijmegen Department of Organic Chemistry
Bioassay: germination activity towards seeds of Bioassay: germination activity towards seeds of O. O. ramosaramosa
11aα OH down, D-ring down (natural); 11aβ OH down D-ring up
16bα OAc up, D-ring down;16bβ OAc up; D-ring up
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Radboud University Nijmegen Department of Organic Chemistry
Bioassay: germination activity towards seeds of Bioassay: germination activity towards seeds of O. O. ramosaramosa
12aα: OH down, D-ring down (natural); 12aβ: OH down, D-ring up17bα: OAc up, D-ring down; 17bβ: OAc up, D-ring up
18α: oxo, D-ring down (remarkably active); 18β: oxo, D-ring up
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Radboud University Nijmegen Department of Organic Chemistry
OO
O O O
A 5-Deoxy-strigol has been isolated and identified as a branching factor for arbuscular
Mycorrhizal Fungi. Akiyama et al. Nature, 453, 824 (2005); Parniste, Nature, 435, 750 (2005).
Strigol, sorgolactone and GR24 are also highly active!
••StrigolactonesStrigolactones apparently have symbiotic functionsapparently have symbiotic functions
••Weeds thrive best in soil of low fertilityWeeds thrive best in soil of low fertility
••N and P deficiency promote stimulant productionN and P deficiency promote stimulant production
••AM fungi improve P level in the soilAM fungi improve P level in the soil
BB StrigolactonesStrigolactones as new hormone class in regulating above ground plant architectas new hormone class in regulating above ground plant architectureure
••Active as inhibitor for Active as inhibitor for shoot shoot branching branching andand bud outgrowthbud outgrowth
•• UmeharaUmehara et alet al, Nature, 2008; Gomez, Nature, 2008; Gomez--RoldanRoldan et al,et al, Nature, 2008Nature, 2008
C QuestionC Question: structure activity relationship, : structure activity relationship, bioactiphorebioactiphore, receptor protein, , receptor protein,
same as for germination?same as for germination?
Newly discovered functions of Newly discovered functions of strigolactonesstrigolactones
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Radboud University Nijmegen Department of Organic Chemistry
The Huygens Building ; Radboud University NijmegenThe Huygens Building ; Radboud University Nijmegen
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Radboud University Nijmegen Department of Organic Chemistry
New New StrigolactoneStrigolactone Analogues, Design, Synthesis Analogues, Design, Synthesis
and Bioactivityand Bioactivity
� Thank you for your attention