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The syntheses of optically pure 4,4‐dimethyl‐L‐glutamic acid as well as (2S,4R)‐ and (2S,4S)‐4‐hydroxy‐4‐methylglutamic acids have been achieved by transamination of the corresponding 2‐oxo‐4,4‐dimethyl‐ and rac‐2‐oxo‐4‐hydroxy‐4‐methylglutaric acids using glutamic oxalacetic transaminase (GOT).

A New Access to Alkyl-α-ketoglutaric Acids, Precursors of Glutamic Acid Analogues by Enzymatic Transamination. Application to the Synthesis of (2S,4R)-4-Propyl-glutamic Acid.-The new ketoglutarate (V) is easily available by a novel route via Claisen-Johnson rearrangement of ester (I) with orthoester (II), followed by oxidation of the ethylidene group and hydrolysis of the ester groups. Transamination of propylketoglutarate (V) with only 0.33 equivalents of cysteine sulfinic acid (ACS) as amino group donor catalyzed by glutamic oxalacetic transaminase yields the glutamic acid derivative (VI) in 98% purity. In the presence of excess ACS a 75:25 diastereomeric mixture of (VI) and its (2S,4S)-isomer is obtained. -(HELAINE, VIRGIL; ROSSI, JOEL; BOLTE, JEAN; Tetrahedron Lett. 40 (1999) 36, 6577-6580; Dep. Chim., Univ. Blaise Pascal, F-63177 Aubiere, Fr.; EN)