Use of catalytic antibodies for synthesizing epothilone

Details Use of catalytic antibodies for synthesizing epothilone Use of catalytic antibodies for synthesizing epothilone

1999-10-08

2001-09-25

Patterson, Jr., Charles L. (Department: 1652)

Chemistry: molecular biology and microbiology

Process of utilizing an enzyme or micro-organism to destroy...

Resolution of optical isomers or purification of organic...

C435S188500

Reexamination Certificate

active

06294374

ABSTRACT:

FIELD OF INVENTION
The invention relates to catalytic antibodies having aldolase activity. More particularly the invention relates to a process for enantioselectively purifying a racemic mixture of aldol synthons by means of an antibody catalyzed retro-aldol reaction.
BACKGROUND
Reactive immunization provides a unique opportunity to generate catalytic antibodies that are efficient yet broad in scope (Shultz, P. G., et al.,
Science
1995, 269, 1835; Keinan, E., et al.
Israel J. Chem.
1996, 36, 113; and Reymond, J.-L.
Top. Curr. Chem.
1999, 200, 59). Recently, two aldolase antibodies 33F12 and 38C2 were generated against a &bgr;-diketone hapten, 6-(4-glutaramidophenyl)-hexane-2,4-dione, using reactive immunization (Wagner, J., et al.,
Science
1995, 270, 1797). These antibody catalysts were found to be useful synthetic catalysts in that they catalyze a wide range of aldol- and retro-aldol reactions, typically with a very high degree of enantioselectivity (Zhong, G., et al.,
J. Am. Chem. Soc.
1997, 119, 8131; List, B., et al.,
Chem. Eur. J.
1998, 4, 881; Hoffmann, T., et al.,
J. Am. Chem. Soc.
1998, 120, 2768; Barbas, C. F, et al.,
Science
1998, 278, 2085; Zhong, G., et al.
Angew. Chem. Int. Ed. Engl.
1998, 37, 2481; and List, B., et al.,
J. Am. Chem. Soc.
1999, 121, 7283).
Epothilones A-E, 2-6, are sixteen-membered macrolides isolated from myxobacteria, i.e.,
Sorangium cellulosum
strain 90 (Bollag, D. M., et al.,
Cancer Res.
1995, 55, 2325; Gerth, K., et al.,
J. Antibiot.
1996, 49, 560; Hofle, G., et al.,
Angew. Chem. Int. Ed. Engl.
1996, 35, 1567; and Nicolaou, K. C., et al.,
Angew. Chem. Int. Ed. Engl.
1998, 37, 2014). Several total syntheses of epothilones A-E as well as their analogs have been achieved. For the first total syntheses of epothilones A-D, see: (a) Balog, A., et al.,
Angew. Chem. Int. Ed. Engl.
1996, 35, 2801; Su, D.-S., et al.,
Angew. Chem. Int. Ed. Eng.
1997, 36, 757. Syntheses of epothilones A and C were simultaneously reported by Nicolaou and Schinzer groups (Schinzer, D., et al.,
Angew. Chem. Int. Ed. Engl.
1997, 36, 523; and Nicolaou, K. C., et al.,
Angew. Chem. Int. Ed. Eng.
1997, 36, 525). For the synthesis of epothilone E, see: Nicolaou, K. C., et al.,
Angew. Chem. Int. Edn. Eng.
1998, 37, 84. For the recent total synthesis of other epothilones see: May, S. A., et al.,
Chem. Commun.
1998, 1597; Mulzer, J., et al.
Tetrahedron Lett.
1998, 39, 8633; Harris, C. R., et al.
Tetrahedron Lett.
1999, 40, 2263; Nicolaou, K. C., et al.,
Chem. Commun.
1999, 519; Nicolaou, K. C., et al.,
Bioorg. Med. Chem.
1999, 7, 665; and White, J. D., et al.,
J. Org. Chem.
1999, 64, 684. The biological properties of epothilones A-E and their analogs have also been recorded (Chou, T.-C., et al.,
Proc. Natl. Acad. Sci. USA
1998, 95, 9642 and references cited therein). Recently, a synthesis of the naturally occurring epothilones A-D, 2 and 4, starting from aldol products obtained either by an antibody 38C2-catalyzed aldol addition of acetone to the aldehyde 10 or by an enantioselective resolution of a racemic aldol product using antibody 38C2 (Sinha, S. C., et al.,
Proc. Natl. Acad. Sci. USA
1998, 95, 14603).
SUMMARY
It is disclosed herein that catalytic antibodies 84G3, 85H6 and 93F3 have antipodal reactivity with regard to catalytic antibody 38C2 and that these antibodies are effective with regard to the catalytic resolution of the thiazole aldols 9a-k on a preparative scale. It is further disclosed that this antibody-based synthon approach provides an attractive synthetic route to natural epothilones and their 13-alkyl derivatives as exemplified here with syntheses of epothilone E, 6, 13-alkyl epothilone C, 7 and their trans isomers.
Catalytic antibodies 84G3, 85H6 and 93F3 were generated against hapten 1 and have been deposited with the ATCC. Like 33F12 and 38C2, these antibodies also catalyze aldol reactions with a wide variety of aldehydes and ketones via an enamine mechanism. However, the aldol products prepared with these new antibodies are antipodal as compared to those obtained by catalysis with the antibodies 33F12 and 38C2. Two of the new catalysts, 84G3 and 93F3, operate with the highest catalytic proficiencies yet observed with antibodies, (k
cat
/K
m
)k
un
>10
13
M
−1
. These new catalysts present significant advantages with regard to the synthesis of epothilones and their analogs.
One aspect of the invention is directed to a process for enantioselectively resolving a racemic mixture of an aldol synthon. The racemic mixture includes a first and a second enantiomer of the aldol synthon. The racemic mixture need not be a 50/50 mixture of the two enantiomers. In the first step of the process, the first enantiomer of the aldol synthon is enantioselectively converted to form an aldehyde product by means of a retro-aldol reaction catalyzed by a catalytic antibody. The second enantiomer of the aldol synthon is left unmodified in this process. The aldehyde product is then separated from the unmodified second aldol synthon to achieve an enantioselective resolution of the aldol synthon. Preferred catalytic antibodies include 84G3, 85H6, and 93F3. In a preferred mode, the synthons and the retro-aldol reaction are represented as follows:
Preferred substituents for R
1
include Me, CH
2
OH, SMe, and OMe. Preferred substituents for R include Me, Et, n-Pr, n-Bu, n-Pentyl, and n-Bu-1-en-4-yl.


REFERENCES:
patent: 5733757 (1998-03-01), Barbas et al.
Barbas, C.F., et al. (1997) Science 278, 2085-2092.*
List, B., et al. (1999) J. Am. Chem. Soc. 121(32), 7283-7291.*
Hoffmann, T., et al. (1998) J. Am. Chem. Soc. 120(12), 2768-2779.*
Shulman, H., et al. (1999) Bioorg. Med. Chem. Lett. 9, 1745-1750.*
Sinha, S. C., et al. (1998) Proc. Natl. Acad. Sci, USA 95, 14603-14608.*
Schultz, et al., “From Molecular Diversity to Catalysis: Lessons from the Immune System”,Science 269: 1835-1842 (1995).
Wagner, et al., “Efficient Aldolase Catalytic Antibodies That Use the Enamine Mechanism of Natural Enzymes”,Science 270: 1797-1800 (1995).
Keinan, et al., “The First Decade of Antibody Catalysis: Perspective and Prospects”,Israel J. Chem. 36: 113-119 (1996).
Zhong, et al., “Antibody-Catalyzed Enantioselective Robinson Annulation”,J. Am. Chem. Soc. 119: 8131-8132 (1997).
List, et al., “Enantioselective Total Synthesis of Some Brevicomins Using Aldolase Antibody 38C2”,Chem. Eur. J. 4: 881-885 (1998).
Zhong, et al., “Catalytic Enantioselective Retro-Aldol Reactions: Kinetic Resolution of &bgr;-Hydroxyketones with Aldolase Antibodies”,Angew. Chem. Int. Ed. Engl. 37: 2481-2484 (1998).
Reymond, “Catalytic Antibodies for Organic Synthesis”,Top. Curr. Chem. 200: 59-93 (1999).

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