Chiral vicinal diacylamines
Bamberger ring cleavage
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Ring cleavage of ethyl 3-[4(5)-imidazolyl]propanoate (1) with (-)-menthyl chloroformate introduces chiral carbamate substituents on the double bond which, upon hydrogenation, induces preferred formation of ethyl (4S)-4,5-bis[(-)-menthyl-oxycarbonylamino]pentanoate (5) (5:1 ratio of diastereomers). The ring cleavage benzoylation product of (S)-histidine methyl ester, with a chiral center in the side chain, gives rise to (2S,4R)/(2S,4S)-2,4,5-tribenzamidopentanoates (13, 14), in 2:1 ratio upon hydrogenation.
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