Sodium borohydride → L-Proline 1,1-dimethylethyl ester

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Reaction Steps

0.55 g (0.93 mmol) of N-[[N-[N-(benzyloxycarbonyl)-L-glutaminyl]-L-phenylalanyl]methyl]-L-proline tert.butyl ester, prepared as described in Example 6, was reduced in 15 ml of isopropanol in the presence of 90 mg of sodium borohydride as described in Example 7. After working-up, the product was chromatographed on silica gel using 2% methanol in chloroform for the elution. There were obtained 60 mg of isomer 1 of N-[3(S)-[[N-(benzyloxy-carbonyl)-L-glutaminyl]amino]-2(R or S)-hydroxy-4-phenylbutyl]-L-proline tert.butyl ester in the form of a solid; Rf (System B): 0.37; MS: m/e 597 [M+H]+, and 65 mg of isomer 2 in the form of a solid; Rf (System B): 0.25; MS: m/e 597 [M+H]+.

Provenance & Evidence