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Aymmetric synthesis of (R) - and (S)-citramalate in high enantiomeric purity

✍ Scribed by Stephen V. Frye; Ernest L. Eliel

Publisher
Elsevier Science
Year
1985
Tongue
French
Weight
239 KB
Volume
26
Category
Article
ISSN
0040-4039

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✦ Synopsis

Sumnary. An asymmetric synthesis of both isomers of dimethyl P-acetoxycitramalate in over 96% enantiomeric excess is described.

Citramalic

acid is a member of the 2-alkylmalic acid family and has been isolated from a variety of natural sources. Its structure was determined and a method for its preparation described in the late 19th century; 132 however, its absolute configuration was not determined until 1965 by correlation with mevalolactone. 3 Resolution4" and enzymatic synthesis6 have until recently been the only source of optically pure citramalic acid. A number of asymmetric chemical syntheses of either (RI-or (S)-citramalic acid have appeared in the last decade, 7-11 but only one group" has reported material of acceptable (85%) enantiomeric purity. The use of citramalic acid as a chiral synthon in prostaglandin synthesis 12 makes its preparation of particular interest. We describe here an asymmetric synthesis of dimethyl (RI-(+I-and (S)-(-j-2acetoxycitramalate in over 96% enantiomeric excess using a chiral 1,3-oxathiane adjuvant developed by our group. 13-16 The synthesis is summarized in Scheme 1.

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