Page 155 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

142 hydrolysis, oxidation and reduction

and 128.0, 128.3 and 128.4, and 136.3 and 136.5, 154.4 and 154.8, 169.8 and
170.0 (resonances are doubled due to hindered rotation).
Rotation was recorded on a JASCO-DIP-370 instrument: [a] 26 ‡ 21:87
D
(c 1.996, CH 2 Cl 2 ).

Conclusions
The reduction of b-keto esters by bakers' yeast is a convenient method for
establishing multiple chiral centres in a single step. The procedure is very simple
and can be carried out on a large scale. Isolation of the product is often
problematic if one uses the yeast directly. The procedure using immobilized
[7]
yeast allows for easy work up and higher chemical yield . The present work is
a modification of the procedure for the reduction of N-BOC-3-ketoproline ethyl
ester originally reported by Knight et al. [8] The product hydroxyproline has
served as a starting material in the synthesis of the indolizidine alkaloid slafra-
[9]
mine .

REFERENCES
1. Bertschy, H., Chenault, H.K., Whitesides, G.M. Enzyme Catalysis in Organic Syn-
thesis; VCH: Weinheim, New York, 1995; Vol. II.
2. Servi, S. Synthesis 1990, 1.
3. Csuk, R., Gla Ènzer, B.I. Chemical Reviews 1991, 91, 49.
4. Roberts, S.M. Preparative Biotransformations Wiley, Chichester, 1997.
5. Any supermarket variety is applicable.
6. Cooper, J., Gallagher, P.T., Knight, D.W. J. Chem. Soc., Chem. Commun., 1988, 509.
7. Nakamura, K., Kawai, Y., Oka, S., Ohno, A. Tetrahedron Lett., 1989, 30, 2245 and
references therein.
8. This procedure utilizes N-BOC-3-ketoproline ethyl ester as the substrate: Knight,
D.W., Sibley, A.W. J. Chem. Soc., Perkin Trans. 1, 1997, 2179.
9. (a) Sibi, M.P., Christensen, J.W., Li, B., Renhowe, P. J. Org. Chem., 1992, 57, 4329.
(b) Sibi, M.P., Christensen, J.W. J. Org. Chem., 1999, 64, 6434.