Yamakawa Chemical Industry Co., Ltd.

Koji Ohsaka

Kenichi Sakai

Hisamichi Murakami

Hirofumi Noda

Disclosed are a novel process for preparing D-alloisoleucine and an improved process for epimerizing L-isoleucine to prepare D-alloisoleucine. In the former process, (2S, 3S)-tartaric acid derivative of formula I below; wherein R stands for a hydrogen atom, a C,-C,lower alkyl group, lower alkoxy group, chlorine atom, bromine atom and nitro group; and &ldquo;n&rdquo; is a number of 0, 1 and 2; is combined with an epimer mixture of L-isoleucine and D-alloisoleucine in a reaction medium to form a complex of D-alloisoleucine and the compound of formula I. The precipitated complex is decomposed by putting it in an alcohol to isolate D-alloisoleucine. In the latter process, L-isoleucine is suspended in an inert solvent which does not substantially dissolve amino acids, and epimerized in the presence of C,-C,saturated lower fatty acid and salicylaldehyde.

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Tokyo, Japan

Koji Ohsaka