(4S, 3S)-4-Amino-3-hydroxy-6-methylheptanoic acid (AHMHA) の不斉合成に関する研究

概要

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An asymmetric synthesis of 4-amino-3-hydroxy-6-methylheptanoic acid (AHMHA, 9), an amine moiety of pepstatins, from L-leucine has been studied. The reaction of N-phthalyl-L-leucyl chloride (3) with ethyl tert-butyl malonate (4b) and (-)-menthyl-tert-butyl malonate (4c) afforded the corresponding 5b and 5c, which were easily derived to 7b and 7c, respectively, by decarboxylation under mild conditions without racemization of the chiral center (C-4). Reduction of 7b with sodium borohydride gave the mixture of two diastereomers (8b1 and 8b2; 67:33), which were hydrolyzed with 4 N-hydrochloric acid to afford the corresponding diastereomer 9 (4S, 3S)and 10 (4S, 3R), respectively. These compounds were separated by ion-exchange resine (H+ form) chromatography. Similarly, the reaction of 7c to 8c1 and 8c2 (58:42), and subsequent hydrolysis afforded the mixture of 9 and 10. The extent of asymmetric reduction was examined by the GLC analysis of the TMS derivatives of 8b and 8c.
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