1 bryostatins: selected syntheses biological activity, and analogue design hao peng beauchemin...
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1
Bryostatins: Selected SynthesesBiological Activity, and Analogue Design
Hao Peng
Beauchemin Research GroupDepartment of Chemistry
University of Ottawa
O
H3COOC
O
O
C
AB
HO
OH
O
O
OH
O
COOCH3
O
C
http://student.britannica.com/eb/art/print?id=86904&articleTypeId=0
2
Outline
• Introduction
Bryozoan and bryostatin Pharmaceutical applications Limited resources and possible solutions
• History of bryostatins total syntheses
• Trost’s Bryostatin-16 total synthesis (2008)
• Biological activities study and Wender’s analogue design
• Conclusion
3
The Marine Bioactive Product
Bryostatin was first discovered in Bugula neritina, a species of bryozoan, at the gulf of Mexico in 1968.
Bugula neritina
It was produced by Endobugula sertula, a symbiont bacteria of the bryozoan.
The compound was found to protect bryozoan larva from predation or infection.
Bryostatin has biomedical potential and can be used as an anti-cancer agent as well as memory enhancement agent.
http://www.uq.edu.au/meeg/images/bugula_neritina.jpg
4
California
Gulf of Mexico Gulf of Japan
5
Bryostatin Family
O
O
H3COOC
COOCH3
O
OH
OOH
O
OR1HO
1
5
79
30
1516 17
19
34
Bryostatin 1,2, 4-15, 18(10,11,13,18 only have C7 substituent)
R2O
OH
20
O
O
H3COOC
COOCH3
O
OH
OOH
O
OPivHO
1
5
79
30
1516 17
19
20
34
Bryostatin 16Bryostatin 17 (C21-C34 isomer)
O
O
H3COOC
O
OH
OOH
O
OR1HO
1
5
79
30
1516 17
19
34
OH
O
O
R2O 20
20 members of bryostatin have been isolated and characterized.
AB
C
AA
BB
C C
Bryostatin 3, 19, 20(Bryostatin 3, 19 only haveC20 substituent)
Hale; Hummersone; Manaviazar; Frigerio Nat. Prod. Rep. 2002, 19, 413Schaufelberger et al J. Nat. Prod. 1991, 54, 1265Pettit; Gao; Blumberg; Herald; Coll; Kamano; Lewin; Schmidt; Chapuis J. Nat. Prod. 1996, 59, 286
6
Bryo-1: Chemotherapeutic Object
In 1982, structure of the most abundant member, Bryostatin 1, was determined after the challenging
Isolation by Pettit, Clardy, and coworkers at the Arizona State Cancer Institute and Cornell University.
Pettit; Herald; Doubek; Herald; Arnold; Clardy J. Am. Chem. Soc. 1982, 104, 6846Smith; Smith; Pettit Biochem. Biophys. Res. Comm. 1985, 132, 939
O
H3COOC
O
OAc
C
HO
OH
O
O
OH
O
COOCH3
O
OH H
Bryostatin 1
On-Pr
7
Potent Chemotherapeutic Candidate
In National Cancer Institute (NCI):
38 clinical trials of bryostatin 1 were doneor being underway currently.
15 trials of bryostatin 1 combining with other chemotherapeutic agents are in Phase II as well.
Doses required in vivo are extremely low.
Condition Intervetion Phase
Kidney Cancer Drug: bryostatin 1
Phase II
Leukemia
Myelodysplastic Syndromes
Drug: bryostatin 1
Phase II
Multiple Myeloma and Plasma Cell Neoplasm
Drug: bryostatin 1
Phase II
Colorectal Cancer Drug: bryostatin 1
Phase II
Breast Cancer Drug: bryostatin 1
Phase II
Ovarian Cancer Drug: bryostatin 1
Phase II
Lymphoma Drug: bryostatin 1
Phase II
Head and Neck Cancer Drug: bryostatin 1
Phase II
http://clinicaltrials.gov/.
Sanjeev. B. et al. J. Nat. Prod. 2008, 71, 492
8
More recent research proved bryostatin is helpful to improve learning ability as well as memory retention.
Alzheimer’s disease was observed by Dr. Alois Alzheimer in 1901, and the main symptom was great memory loss.
According to Alzheimer’s disease statistics (USA, 2004) The 7th leading cause of death, causing mortality in 65,829 people; The third most expensively treated disease;
More than 5 million Americans are estimated to currently have it;
Projected that by 2050, that number will exceed 14 million
Memory Enhancement Agent
Jarin. H. and Daniel. L. A, PNAS, 2007, 104, 19571
In NCI, the clinical trail of Bryostatin 1 to Alzheimer’s disease is underway.
http://www.metromusictherapy.com/alz_stroke_park.asp
9
Limited Supply and Possible Solutions
Solutions:
1) Aquaculture: time-consuming
2) Biosynthesis: still underway
3) Total synthesis: can provide material on gram scale
Schaufelberger et al. J.Nat.Prod. 1991, 54, 1265Thakur; Jain; Natalio; Hamer; Thakur; Müller Biotech. Adv. 2008, 26, 233Sudek,S. et al. J. Nat. Prod. 2007, 70, 67Kerr; Lawry; Gush Tetrahedron Lett. 1996, 37, 8305
The production is expensive, and will cause ecological issue.
14 Tonnes
Isolation completed in 10 months
18 grams
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
HO
O
On-Pr
OH
Bryostatin 1Bugula neritina
10
Outline
• Introduction
Bryozoan and bryostatin Pharmaceutical applications Limited resources and possible solutions
• History of bryostatins total syntheses
• Trost’s Bryostatin-16 total synthesis (2008)
• Biological activities study and Wender’s analogue design
• Conclusion
11
The History of Total Synthesis
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
HO
AcO
Bryostatin 7
O O
H3COOCOH
O
COOCH3
O
OH
OOH
HO
O
O
Bryostatin 2
O O
H3COOCOAc
O O
O OH
OOH
HO
O
OOBryostatin 3
All the 3 total syntheses required more than 70 steps and over 40-step longest linear sequences. Therefore, they are inefficient methods for material supply.
Kageyama; Tamura; Nantz; Roberts; Somfai; Whritenour; Masamune J. Am. Chem. Soc. 1990, 112, 7407Evans; Carter; Carreira; Charette; Prunet; Lautens J. Am. Chem. Soc. 1999, 121,7540Ohmori; Ogawa; Obitsu; Ishikawa; Nishiyama; Yamamura Angew. Chem. Int. Ed. 2000, 39, 2290
After bryostatin was founded in 1968, only 3 total syntheses were reported in 32 years.
1990 Masamune 1999 Evans 2000 Nishiyama and Yamamura
n-Pr n-Pr
12
Main Synthetic Challenges
Main challenges in bryostatin synthesis:
1) Three heavily substituted
tetrahydropyran rings
2) The congested E-alkene of C16-17
3) Two base/acid sensitive exo-cyclic
enoates
4) A numerous Oxygen-containing
functionalities on the macro-lactone.
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
HO
O
O
OH
Bryostatin 1
B A
C
1617
n-Pr
13
Strategies In Common
O O
H3COOCOR2
O
COOCH3
O
OH
OOH
HO
R1O
Bryostatin 2: R1= COC7H11, R2=H
Julia-olefination(2) Yamaguchi
macrolactonization (1)OH
O
RO
LG
OH
B13
10
16
(+)
(+)
O
PhO2SMe Me
OR
OR
CO2H
A9
(-) O
C20
OR
Me OR
H
Me
SO2Ph
Me 17(-)
Evans; Carter; Carreira; Charette; Prunet; Lautens J. Am. Chem. Soc. 1999, 121,7540
171
25
16
Evans 1999 :
AB
C
14
Yamaguchi Macrolactonization
O
HO
HO
n
+ Cl
Cl
Cl
COCl
NEt3 (1.1 eq)THF, r.t, 2h
hydroxy acid 2,4,6-trichlorobenzoylchloride (1.1 eq)
Cl Cl
Cl O
O
O
HO
n
mixed anhydride
solvent, DMAP
O
O
n
Medium- or large- ring lactone
Laszlo K et Barbara Czako, in Strategic applications of named reactions in organic synthesis, p500Evans; Carter; Carreira; Charette; Prunet; Lautens J. Am. Chem. Soc. 1999, 121,7540
Main advantages:
1) Operational simplicity
2) High reacting rate
3) Lack of by-products
O O
H3COOCOR2
O
COOCH3
O
OH
OOH
HO
R1O
Bryostatin 2: R1= COC7H11, R2=H
OH
15
Julia Olefination
Main features:
1) High (E)-stereoselectivity
2) The (E)-selectivity is increased with increasing chain branching of R1,R2 and R3.
3) Strong basic reaction condition
O O
H3COOCOR2
O
COOCH3
O
OH
OOH
HO
R1O
Bryostatin 2: R1= COC7H11, R2=H
OH
S R1Ph
OO Base
R2 R3
O
S R1Ph
OO
R3 OR2
R4 LG
O
S R1Ph
OO
R3 OR2 O
R4
Na (Hg), EtOHR2 R3
R1H
(E)- Alkene
R1= H, alkyl, aryl; R2, R3= H,alkyl, aryl, alkenyl; R4=alkyl, aryl; LG= Cl, Br, COOR
Laszlo K et Barbara Czako, in Strategic applications of named reactions in organic synthesis, p230
16
Julia Olefination
Mechanism:
SO2
R1
Ph
H
H OR2
O
R4
Na(Hg), MeOH
Na
S R1
Ph
R2 H
OO
Na(Hg)
SETS R1
Ph
R2 H
OO Na NaO2SPh
R1
R2 H
R1
H R2Na(Hg)
SET
R1
R2 HMeOH
R1
R2 H
H(E)- AlkeneVinyl anionVinyl radicals
Vinyl sulfoneOMe
Acyloxy sulfone
Laszlo K et Barbara Czako, in Strategic applications of named reactions in organic synthesis, p230
17
Drawback of Julia-Olefination
O
RO
LG
OH
B13
10
16
OC
20
OR
Me OR
H
Me
SO2Ph
Me 17
O O
H3COOCOH
O
COOCH3
O
OH
OOH
HO
O
On-Pr
OH
Bryostatin 2
7B A
C
O O
RO OR
O O
OR
OOR
MeO
7B A
C
(+)
(+)
(-)
O
PhO2SMe Me
OR
OR
CO2H
A9
(-)
O
LG
OH
B13
10
16
O
C20
OR
Me OR
H
Me
SO2Ph
Me 17
(+)
(+)
(-)
O
PhO2SMe Me
OR
OR
CO2H
A9
(-)MeO2C
CO2CH3
transform 1
transform 2
×
Numerous protecting groups for introduction of exo-cyclic enoate.
Bryostatin 2 synthesis (Evans et al, 1999)
18
Two Solutions
Function-Oriented Synthesis (FOS): maintaining biological activities but simplifying structure (analogue design).
Wender; Verma; Paxton; Pillow Acc. Chem. Res. 2008, 41, 40
19
Outline
• Introduction
Bryozoan and bryostatin Pharmaceutical applications Limited resources and possible solutions
• History of bryostatins total syntheses
• Trost’s Bryostatin-16 total synthesis (2008)
• Biological activities study and Wender’s analogue design
• Conclusion
20
O
O
H3COOC B
C
COOCH3
O
OH
OOH
O
OPivHO
A
1
5
79
30
1516
1719
20
34
Bryostatin 16
Ru- catalyzed coupling
Pd-catalyzed coupling
The Revolutionary Step in Bryostatin Total Synthesis
In 2008, Barry M. Trost and Guangbin Dong reported a total synthesis of bryostatin 16.
Barry M. Trost
Main features:
1) Instead of Julia-olefination, E-alkene on C16-17 was stored in precursor in advance
2) Application of ruthenium-catalysed ene-yne coupling for B ring formation
3) Application of palladium-catalysed yne-yne coupling for C ring formation
4) Much shorter synthesis route (39 total, 26 linear)
Trost and Dong Nature 2008, 456, 485
21
Metathesis Approach to Bryostatins
O O
OO
OBn
H
H
MeO
OSEMO
OMe
H
HGrubbs 225-30%
O O
OO
OBn
H
H
MeO
OSEMO
OMe
H
H
O O
OO
OBn
H
H
MeO
OSEMO
OMe
H
H
MeMe
O O
OO
OBn
H
H
MeO
OSEMO
OMe
H
H
MeMe
18 18
×
In 2006, Thomas E. J. :
Ball; Bradshaw; Dumeunier; Gregson; MacCormick; Omori; Thomas Tetra Lett 2006 47 2223
When a geminal dimethyl group is on Carbon 18, the reaction did not work because of steric hinderance.
( E:Z=1:1)
22
A Ring-Expanded Analogue Design
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
HO
O
On-Pr
OH
Bryostatin 1
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
H3CO
AcO
OH
16
1732
28
29
30 31Ring closingmetathesis
B A
C
O O
H3COOCOAcH3CO
B A
COOH
OTES
O
COOCH3
OH
OTESAcO
OH
C
H+
TMS
OPMBHO OO
OTBS
O OPMB
+
O
COOCH3
O
OAcO
O
C
H
TBSO
Ru-catalyzed tandemTetrahydropyran formation
CH3
H3CO2C OO
OH
+ OTBS
Pd(II)-catalyzed tandemDihydropyran formation
O
COOCH3
O
OC
H
TBSO
Trost; Yang; Thiel; Frontier; Brindle J.Am.Chem.Soc 2007 129, 2206
Barry M. Trost (2007):
23
R2
O
HO
TMS
R1
+
Ene-Yne couplingOH
R2
O
R1
TMS
hydroxyenone intermediate
Michael addition
O
R2
O
R1
TMS
[CpRu(CH3CN)3]PF6
O
H
HH
HHH R1
TMS
trans-isomer
(3 eq)
(1 eq)Ru
OH
TMS O
R2
O
OH3COOC B
C
COOCH3
O
OH
OOH
O
OPivHO
A
1
5
79
30
1516
1719
20
34
Bryostatin 16
homopropargylicalcohol
,-enone
OR2
R1
Main features:
1) Mild reaction condition: alkyne ([0.5M]), catalyst (10 mol%), acetone, rt,40h;
2) Isolated yield: 39-80% (10 entries);
3) cis/trans ratios ranged from 5/1 to 8/1;
4) Complete chemoselectivity.
5) Convergent further functionalization of TMS group.× No equilibrium
Trost; Yang; Wuitschik, Org Lett 2005, 7, 4761Miller Angew. Chem. Int. Ed. 2009, 48, 2
Tandem Ru-Catalyzed Alkyne-Enone Coupling / Michael Addition
main product thermodynamic control
24
TMSOPMB
HO
+
O
OPMB
10 mol% [CpRu(CH3CN)3]PF6
acetone, r.t. 40 h, 69%O
O
OPMBTMS
OPMB
TMSOPMB
HO
+
O 10 mol% [CpRu(CH3CN)3]PF6
acetone, r.t. 40 h, 39%
OO
OPMBTMS
OPMB
OPMB
O
OH3COOC B
C
COOCH3
O
OH
OOH
O
OPivHO
A
1
5
79
30
1516
1719
20
34
Bryostatin 16
The reaction tolerated branching
The reaction showed complete chemoslectivity between different alkenes.
No cross-coupling product
Trost; Yang; Wuitschik Org Lett 2005, 7, 4761Trost; Machacek; Schnaderbeck Org Lett 2000, 2, 1761Trost et al Chem Rev 2001, 101, 2070
25
Further Functionalization of Vinylsilane
O
R2
O
R1
TMS
R1=methyl, R2= n-C6H13
TFA, toluene, 0°C to rt, 89%O
R2
O
R1
1) NIS, CH3CN, 90%
2) PdCl2(PhCN)2, dppf, MeOH, CO,97% O
R2
O
R1
MeO2C
1) mCPBA, Li2CO3, DCM,72% (3/1 dr)
2) aq. HBr, MeOH, - 78°C3) BF3.OEt2, DCM, -50°C to 10°C 97% over two steps
O
R2
O
R1
BrO
R2
O
R1
MeO2CPd(PPh3)4, DMF
MeOH, CO
85°C, quant
OO
R2
O
R1
OHO
R2
O
R1
Bryostatins
cleavage reduction
A good handle for functional group inter-conversion
Trost; Yang; Wuitschik Org Lett 2005, 7, 4761Trost and Machacek Angew. Chem. Int. Ed. 2000, 41, 4693Trost; Machacek; Schnaderbeck Org Lett 2000, 2, 1761Chou; Kuo; Wang; Tsai; Sun J. Org. Chem. 1989, 54, 868Qing and Yue Tetra. Lett. 1997, 38, 8067
26
Tandem Palladium-catalyzed terminal alkyne-ynoate coupling/cyclization
R1
O2CH3COH
+
Pd(OAc) , TDMPP,r.t., solvent
24 h
terminal alkyne
alkynoate
H3CO2CR2
R2
O
R1
H3CO2CR2
OH
R1
60 h
OO
R2
R1
O
R1
H3CO2CR2
O
OH3COOC B
C
COOCH3
O
OH
OOHO
OPivHO
A
1
5
79
30
1516 17
19
2034
Bryostatin 16
5-exo-dig cyclization lactonization
Main features:
1) Mild reaction conditions;
2) High regio- and chemo-selectivity
3) Moderate isolated yield for 2 steps (42~62%);
4) Pd(OAc)2 is the catalyst for both the 2 steps;
5) Geometry of exo-cyclic enoate is mechnism dependant
Trost and Frontier J.Am.Chem.Soc. 2000, 122, 11727Trost; Matsubara; Caringi J.Am.Chem.Soc. 1989, 111, 8745Trost and McIntosh J.Am.Chem.Soc. 1995, 117, 7255
6-endo-dig cyclizationStep 1 Step 2
Only favored whenboth inductive and steric effect on terminal alkyne (R1)
Only favored at high T
2
27
O
O
H3COOC B
C
COOCH3
O
OH
OOH
O
OPivHO
A
1
5
79
30
1516
1719
20
34
Bryostatin 16
HO
O
H3COOC B
O
OTBS
OOTES
O
OHH3CO
A
1617
3
H3COOC
O
H3COOC
CO2H
O
OPMBH3CO
PMBO OH
OTBS
H3COOC
+
OTES
4
5
O
TMS
O
OTBS
OO
OTBDPS
OPMB
O OO
OTBDPS
OPMB
6
OHOTBS
TMS
O
TBSO
78
2
Retrosynthesis of Bryostatin 16
E-alkene functionalitywas stored in precursor 8.
B A
28
O
TBSO
2
1) (-)-(Ipc)2B(allyl), Et2O, -90°C,67%, 94% e.e.2)PMB-Br, NaH,DMF, 90%
OPMB
TBSO
OsO4 (2 mol%), 2,6-lutidine,NaIO4, dioxane/water (3:1), 87%
PMBO
TBSOCO2CH3
OH
5 3
OPMB
TBSO O
OTMSOTMS
OCH3
Ti(O-i-Pr)2Cl2, toluene,-78 °C, 69% over 2 steps, ~ 10:1 dr at C(5)
PMBO
TBSO
O
CO2CH3
OH
5 3 Me4NBH(OAc)3, AcOH/CH3CN,- 35 °C, 96%,15:1 dr at C(3)
OH
( S )-
( S )-
Synthesis of A Ring Precursor
Evans; Chapman; Carreira J. Am. Chem. Soc. 1988, 110, 3560Brown and Jadhav J. Am. Chem. Soc. 1983, 105, 2092Brownbridge; Chan; Brook; Kang Can. J. Chem. 1983, 61, 688Evans; Carter; Carreira; Prunet; Charette; Lautens Angew. Chem. Int. Ed. 1988, 37, 2354
29
Synthesis of A Ring Precursor
10 mol% of Otera's catalyst,hexane,reflux
TBSO 5
O
OH
O
3
TBSO 5
O
OTBDPS
O
3TBDPSCl, imidazole,DMF, 50 °C, quantitative
Bu2Sn
NCS SnBu2
O
O
Bu2Sn
SnBu2
SCN
SCN
SCN (Otera's catalyst)
AcOH/H2O (4:1), 69%
HO 5
O
OTBDPS
O
3 1) DMP oxidation2) allyl iodide, In, DMFrt, 66% over 2 steps3) DMP oxidation, 85%
5
O
OTBDPS
O
3
OPMBO
7
PMBO
PMBO
PMBO
PMBO
TBSOCO2CH3
OH
5 3
OH
Otera; Yano; Kawabata; Nozaki Tetrahedron Lett. 1986, 27, 2383
30
O
OTBS
2
Br
H OCH2CH3
H
t-BuLi, (CH3)2Zn, then 2, ether, -78°C; then Na2SO4, r.t.97%
O OTBS OTBS
OHTMSTMSBr
indium powder, InF3 (10 mol%)THF, 65°C , 68%
OTBS
OHTMS1) DMP, NaHCO3, DCM
2) (S)-2-methyl-CBS-oxazaborolidine (5 mol%),catecholborane, DCM, -78°C, 90%, 90% e.e. over 2 steps
(R)-8
O
OHO
H3COOC
Cu(OTf)2 (3 mol%), toluene, -10 °C
NH
H3CO
O
OPMBO
H3COOC
PPTS, CH3OH,
93% over 2 steps OH
OHPMBO
H3COOC
TBSOTf, 2,6-lutidine,DCM, -78 °C, 71% OTBS
OHPMBO
H3COOC4
OO
n-BuLi, methyl propiolate,BF3.OEt2, THF, -78 degree, 92%
O
D-Glactonic Acid1,4-Lactone
6 steps
CCl3
OO O
OH
OH
OH
OH
Synthesis of B and C Ring Precursors
Lin; Loh J. Am. Chem. Soc. 2003, 125, 13042Dess; Martin J. Am. Chem. Soc. 1991, 113 , 7277Corey; Helal Angew. Chem. Int. Ed. 1998, 37, 1986Trost; Yang; Thiel; Frontier; Brindle J.Am.Chem.Soc 2007 129, 2206
31
5
O
OTBDPS
O
3
OPMBO
7
(1.2 eq)
+
OTBS
OHTMS
(R)-8
1) CpRu(CH3CN)3PF6 (13 mol%),DCM, 34% (80% b.r.s.m.)2) NBS, DMF, 98%
O
Br
OTBS
O OPMB OO
OTBDPS
CSA (10 mol%), MeOH
0 °C, 93-96%
O
Br
OH
O
OPMB
OTBDPS
COOCH3
A
B
B
H3COPdCl2(CH3CN)2 (10 mol%), dppf (30 mol%),CO (1 atm), MeOH,TEA, DMF, 80 °C,83% (90% b.r.s.m.)
O
H3COOC
OH
O
OPMB
OTBDPS
COOCH3
AB
H3CO
1) DMP oxidation, NaHCO3, DCM, 88%2) Ohira-Bestmann reagent, K2CO3, MeOH, 97%3) TBAF, HOAc, THF, 90% (96% b.r.s.m.)
O
H3COOC
O
OPMB
OH
COOCH3
AB
H3CO
1) (CH3)3SnOH, DCE, 80 °C, 84%;2) TESOTf, 2,6-lutidine, DCM, -78 °C, 71%
Laszlo K et Barbara Czako, in Strategic applications of named reactions in organic synthesis, p402Roth; Liepold; Müller; Bestmann Synthesis 2004,1, 59 Nicolaou; Estrada; Zak; Lee; Safina Angew. Chem. Int. Ed. 2005, 44, 1378
32
O
H3COOC
O
OPMB
OTES
COOH
AB
H3CO
OTBS
OHPMBO
H3COOC4
+
1) 2,4,6- trichlorobenzoyl chloride,TEA, toluene, then 4, DMAP,92%2) DDQ,pH 7.0 buffer, DCM,46%
O
H3COOC
O
OH
C
AB
H3CO
OTES
O
O
OTBS
HO
H3COOC
Pd(OAc)2 (12 mol%), TDMPP (15 mol%),toluene, 56%
O
H3COOC
O
OH
C
AB
H3CO
OTES
O
O
OTBS
HO
COOCH3
O
H3COOC
O
O
C
AB
HO
OTES
O
O
OTBS
O
COOCH3
O
C
TBAF, THF, ~52%O
H3COOC
O
O
C
AB
HO
OH
O
O
OH
O
COOCH3
O
C
39 steps from aldehyde 2 26-step longest linear sequence
Bryostatin 16
1) AuCl(PPh3) (20 mol%), AgSbF6 (20 mol%),NaHCO3, DCM/MeCN, 0 °C to r.t. 73%;2) Piv2O, DMAP, DCM, 50 °C, 62%
Liu; Song; Song; Liu; Yan Org. Lett. 2005, 7, 5409
33
Comparison
O
H3COOC
O
O
C
AB
HO
OH
O
O
OH
O
COOCH3
O
C
# of Steps Bryostatin 2 Bryostatin 16
Formation of rings
(A,B and C)
40 22
Macrolactonization 16 10
FGI for exo-cyclic enoate moiety
9 3
Bryostatin 16
O
H3COOC
O
OH
C
AB
HO
OH
O
O
OH
O
COOCH3
O
On-Pr
OH
C
H
Bryostatin 2
34
Outline
• Introduction
Bryozoan and bryostatin Pharmaceutical applications Limited resources and possible solutions
• History of bryostatins total syntheses
• Trost’s Bryostatin-16 total synthesis (2008)
• Biological activities study and Wender’s analogue design
• Conclusion
35
Function Oriented Synthesis Strategy
The majority (57%: 23% ND + 30% S +4% S*) were derived from natural products, or were designed based on a natural product pharmacophore.
only 5% introduced over this period werenatural products themselves.
Newman J. Nat. Prod., 2007, 70, 461
From 1981 to June 2006, in 1184 New chemical entities (NCEs)
ND: Nature product with semisynthetic modification
N: Nature product
S: Totally synthetic drug with modification of an existing agent.S*: Made by total synthesis, but the pharmacophore Is/was from a natural product.
36
PKC and DAG Binding Activation
Quaternary structure of PKC
Castagna M et al, J. Bio. Chem, 1982, 257, 7847Caponigro F et al, Anti-Cancer Drugs, 1997, 8, 26Mackay and Twelves Endocrine-Pelated Cancer, 2003, 10, 389
PIP2: phosphatidyl inositol-bisphosphate
IP3: inositol triphosphate
DAG: diacylglycerol
Protein kinase C (PKC) is a family of serine/ threonine kinases which affects growth factors, hormones, and neurotransmitters.
PKC is the target of both tumour promoter and inhibitor
Phospholipase C catalyzes PIP2 cleavage to IP3 and DAG
PKC binds with DAG and translocates from the cytosol to plasma membrane
O
O
OH
OR
R
O12
DAG
Plasma membrane
cytosol
37
Tumour promoter / inhibitor
Phorbol esters bind to PKC and result in a tumour promotion.
The tumour inhibiting activities of bryostatin- 1 is also related to its strong affinity to PKC.
Competition: phorbol esters and bryostatin-1 bind to the same sites on PKC.
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
HO
O
On-Pr
OH
Bryostatin 1
OH
O
HO
H
HO
OR
OR
20
4
1312
9
Phorbol ester
PKC
Nishizuka.Y. Nature, 1984,308, 693Taylor and Andzelm Curr. Chem. Bio. 1997, 1, 219Newton, Chem. Rev. 2001, 101, 2353
38
Pharmacophoric Model
Wender et al, Proc. Natl. Acad. Sci. USA 1998, 95, 6624Wender et al, Proc. Natl. Acad. Sci. USA 1988, 85, 7197
In 1988, the groups of Wender, Blumberg, and Pettit reported that a proposed pharmacophoric model to explain competitive binding between the three structure-different PKC activators to the same site on PKC.
Paul.A. Wender
Wender started structure-activity studies of bryostatins in 1986 27 publications on bryologue design, synthesis, biological evaluation.
39
Research findings:
The binding of the bryostatins is only modestly affected by changes in the C4–C16 domainbut diminished significantly by alterations in the C19–C26 domain.
Wender et al. Proc Natl Acad Sci USA, 1988, 85, 7197Pettit et al. Anti-Cancer Drug Design, 1992, 7,101.
40
OO
H3COOC
OAc
O
COOCH3
O
OH
OOH
HO
O
O
n-Pr
OH
AB
C19
26
1
Space domain
Pharmacophoric atoms
Structure-Activity Studies
The groups on C1, C19, and C26 affect PKC binding greatly while A and B rings remotely control the orientationand mobility of the groups in recognition domain.
Recognition domain
41
The region containing the putative pharmacophore was retained in an effort to begin simplifying the structure of these molecules without losing their activity completely.
Selected Bryologues Design
O
OO
C
COOCH3
O
OH
O
OA
1
15
OH
O
C7H15 O
26
H
H
HO
H
B
1998
Ki= 3.4 nM
2002
O
OO
C
COOCH3
O
OH
O
OA
1
15
OH
O
C7H15 O
26
H
H
HO
H
B
Ki= 0.25 nM
O
OO
C
COOCH3
O
OH
O
R
OA
1
15
OH
O
C7H15 O
26
HO
B
2005
R= Ph, Ki= 2.3 nM
R=
9
Br
Ki= 1.9 nMWender et al J. Am. Chem. Soc. 1998, 120, 4534Wender et al J. Am. Chem. Soc. 2002, 124, 13648Wender; Koehler; Sendzik Org. Lett. 2003, 5, 4549Stone et al J. Med. Chem. 2004, 47, 6638
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
HO
O
On-Pr
OH
Bryostatin 1
= nM
42
O
OO
C
COOCH3
O
OH
O
OA
1
15
OH
O
C7H15 O
26
H
H
HO
H
B
O
CHO
C
COOCH3
OH
OTBS
OH
O
C7H15 O
OO
CO2H
OA
H
H
H
OTBDPS
B
Key Strategy of Macrolactonization in Wender’s Analogues
14
43Wender et al J. Am. Chem. Soc. 1998, 120, 4534Wender et al J. Am. Chem. Soc. 2002, 124, 13648Wender; Koehler; Sendzik Org. Lett. 2003, 5, 4549
O
OO
C
COOCH3
O
OH
O
OA
1
15
OH
O
C7H15 O
26
H
H
HO
H
B
Ki= 0.25 nM
O
CHO
C
COOCH3
OH
OBn
OH
O
C7H15 O
OO
CO2H
OA
H
H
H
B
OTES
O
OO
C
COOCH3
O
OH
O
OA
1
15
OH
O
C7H15 O
26
H
H
HO
H
B
1998
Ki= 3.4 nM
reconition domain
+
space domain
24 steps, yield 0.02%
2002
O
CHO
C
COOCH3
OH
OTBS
OH
O
C7H15 O
OO
CO2H
OA
H
H
H
B
OTES
reconition domain
+
space domain
17 steps, yield > 3%
O
CHO
C
COOCH3
OH
OTBS
OH
O
C7H15 O
OO
CO2H
OA
H
H
H
OTBDPS
reconition domain
+
space domain
17 steps, yield > 3%
2003
B
11 steps, yield 11%
Harada; Shintani; Oku J. Am. Chem. Soc 1995, 117, 12346Wender; Mayweg; Vandeusen Org. Lett. 2003, 5, 277
44
O
O
H3COOC B
C
COOCH3
O
OH
OOH
O
OPivHO
A
1
5
79
30
1516
1719
20
34
O
OO
C
COOCH3
O
OH
O
OA
1
15
OH
O
C7H15 O
26
H
H
HO
H
B
Bryologue
Conclusion
Bryostatin 16
Complementary approaches:
1) New methodologies provide more efficient routes
2) Simpler targets allow faster synthesis and retaining biological activities.
45
Acknowledgement
Prof. Andre Beauchemin
Joseph MoranIsabelle DionJean-Gregoire RovedaFrancis LoiseauJennifer PfeifferToni RizkAshley HuntPeter NgChristian ClavetteLei ZhangJ-P Wan Fook Chen
46
Comment
O
CHO
C
COOCH3
OH
OTBS
OH
O
C7H15 O
OO
CO2H
OA
H
H
H
OTBDPS
B
P. A. Wender. 1998
O
OTBDPS
OOPMBO
OTBS
OHTMS
B. M. Trost. 2006
47Bryostatins 3, 19
O O
H3COOCOPiv
O O
OH
OOH
HO
O
O
OH
O O
H3COOCOR1
O O
OH
OOH
HO
O
O
R2O
OH
Bryostatin 20
--------------------------------------------------------------------------------------------------------------------------------
O O
H3COOCOPiv
O
COOCH3
O
OH
OOH
HO
B A
C
1
5
79
30
15
1719
20
34
Bryostatin 16Bryostatiin 17 (C21-C34 isomer)
O O
H3COOCOR1
O
COOCH3
O
OH
OOH
HO
OH
R2O
Bryostatins 1, 2, 4-9, 12, 14, 15
O O
H3COOCOR1
O
COOCH3
O
OH
OOH
HO
OH
Bryostatins 10, 11, 13, 18
Oxidation of C19-C20 alkene Hydration of C19-C20 alkene
Possible synthetic-conversion from Bryostatin 16
Bryostatin 16 can be used insemi-syntheses of others bryostatins.
48
The classes of PKC
pseudosubstrate occupied the substrate-bindingcavity of protein kinase C, thus maintaining theenzyme in an inactive conformation (inhibitor)
The PKC family comprises at least 12 isozymes and can be divided the three classes : (1) Conventional; (2) Novel; (3) Atypical
References: 1) Nishizuka.Y. Nature 1984,308, 6932) Newton.A.C. Journal of Biological Chemistry 1995, 270,28495
49
Analogue modeling and design
Crystal structure research (X-ray)
synthesis NMR analysis Biological test
Crystal structure research:
1) Using molecular mechanics calculations to find out lowest energy structures;
2) Then comparing their conformation with known solid state and solution structures of the bryostatins to find out most structurally similar structure.
Blue: bryostatin 1Yellow: designed analogueReference: Paul. A.W. et al, Proc.Natl. Acad. Sci. USA, 1998, 95, 6624
50
Biological evaluation
Reference: Tanaka Y et al. J Biochem 1986;99:257
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
HO
O
On-Pr
OH
Bryostatin 1
=
Significant activity was observedagainst all cell lines studied. Notably, preliminary experiments indicate that in several cell lines, designed bryostatin analogues have superior activity to bryostatin 1 itself.
51
Synthesis of A Ring Precursor
O
TBSO
2
1) (-)-(Ipc)2B(allyl), Et2O, -90 degree,67%, 94% e.e.
2)PMB-Br, NaH,DMF, 90% OPMB
TBSOOsO4 (2 mol%), 2,6-lutidine,NaIO4, dioxane/water (3:1), 87%
OPMB
TBSO O
OTMSOTMS
OCH3
Ti(O-i-Pr)2Cl2, toluene,-78 degree, 69% over 2 steps, ~ 10:1 dr at C(5)
OPMB
TBSO
O
CO2CH3OH
5 3
Me4NBH(OAc)3, AcOH/CH3CN,- 35 degree, 96%,15:1 dr at C(3) OPMB
TBSOCO2CH3
OH
5 OH
3
10 mol% of Otera's catalyst,hexane,reflux
TBSO 5
PMBO O
OH
O
3 TBSO 5
PMBO O
OTBDPS
O
3TBDPSCl, imidazole,DMF, 50 degree, quantitative
Bu2Sn
NCS SnBu2
O
O
Bu2Sn
SnBu2
SCN
SCN
SCN (Otera's catalyst)
AcOH/H2O (4:1), 69% HO 5
PMBO O
OTBDPS
O
3 1) DMP oxidation2) allyl iodide, In, DMFrt, 66% over 2 steps3) DMP oxidation, 85%
5
O
OTBDPS
O
3
OPMBO
7
Reference: Barry. M. T. et al, JACs 2007, 129, 2206-2207
52
Mechanism:
53
Ring Closing Metathesis and Grubbs Catalyst
In all the three total syntheses (bryostatin 2, 3, and 7), the E-alkene of C16-17 was introduced by Julia-olefination. However, the late introduction of the two exo-cyclic enoates extended synthesis route.
Ring closing metathesis (RCM)
+ CH2=CHR
(Grubbs 2)
Mechanism:
RCM has a poor E-selectivity.
Laszlo K et Barbara Czako, Strategic applications of named reactions in organic synthesis, p12
54
Latest analogue design 2008 and clinical trial
Show most recently synthesis. Show rountes and explain how concise it was .
macrotransacetalization
55
DAG analogues
Research also showed that bryostatin 1 and phorbol esters bind to the same sites on PKC
Why the structure-different compounds can have correlative activities?
O O
H3COOCOAc
O
COOCH3
O
OH
OOH
HO
O
On-Pr
OH
Bryostatin 1
O
O
OH
OR
R
O12
OH
O
HO
H
HO
OR
OR
20
4
1312
9
Phorbol esterDAG
Bryostatin 1 is a potential DAG analogue to compete against phorbol ester, but it is a tumor inhibitor.
Reference: Paul. A. Wender , et al. Proc Natl Acad Sci USA 1986;83:4214
56
PKC Activation: DAG Binding
Before binding with DAG, inactive PKC is in cytosol.
Phospholipase C catalyzes PIP2 cleavage to IP3 and DAG, and initiates intracellular calcium release and PKC activation.
PKC binds with DAG and translocates from the cytosol to plasma membrane.
Then phosporylation of PKC will activate a range of kinases.
PIP2: phosphatidyl inositol-bisphosphate
IP3: inositol triphosphate
DAG: diacylglycerol
H. J. Mackay and C. J. Twelves, Endocrine-related Cancer, 2003, 10, 389
cytosol
Plasma membrane
O
O
OH
OR
R
O12
DAG
57
Phorbol Ester: Potent Tumor Promoter
http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=arev&part=A998&rendertype=figure&id=A1006
Phorbol esters showed a correlation between abilities of tumours promotion and PKC activation.
Phorbol ester directly activate PKC (without detectable Calcium mobilization).
Phorbol esters can substitute for DAG at extremely low concentrations.
Nishizuka.Y. Nature, 1984,308, 693
Competition: phorbol esters and DAG bind to the same sites on PKC