Yamakawa Chemical Industry Co., Ltd.

Hisamichi Murakami

Hiroyuki Nohira

Kenichi Sakai

Koji Ohsaka

Shoko Satoh

Tadashi Tobiyama

Hirofumi Noda

Ken'ichi Sakai

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.

Process for preparing D-alloisoleucine and intermediates for preparation

Process for preparing optically active 2-piperazine-carboxylic acid derivatives, particularly S-enantiomer thereof, in high yield and high optical purity on industrial scale. As the optical resolving agents, easily accessible sulfonamides derived from selected optically active amino acids, such as N-tosyl-L-phenylalanine, N-tosyl-D-phenylglycine, N-tosyl-L-alanine or N-tosyl-L-valine, give excellent results. These resolving agents are stable and easily recovered from the reaction mixture and reused. Resolved 2-piperazinecarboxylic acid derivatives are preferably isolated as 4-t-butoxycarbonyl (Boc) derivatives. Diastereomeric salts (an example being shown below) formed as the intermediates of resolution are novel. ##STR1## �In the formula 'Ar' stands for a phenyl or naphthyl group which may be substituted with one to three C1-C6 alkyl groups, halogen atoms, nitro or alkoxy groups; and n=0 or 1.!

Process for preparing optically active piperazine derivatives and

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Tokyo, Japan

Hisamichi Murakami