The reduction of (5S)-5-alkyl-2,4-dioxopyrrolidines, so-called tetramic acids, by NaBH4 gives only partial diastereofacial selectivity in the case of the N-substituted analogues 9f-i, unlike the carbamate derivatives 9a-3 which give the reduced cis-pyrrolidinones 10betaa-e. Increasing the steric hindrance of either the N- or C-5-substituents enhances the re-face selectivity. On the other hand, reduction of the heterobicyclic compound 9n leads to a dramatic reversal of the stereoselectivity. Preliminary calculations show that the N-atom of the ring is slightly pyramidalized; the direction of hydride addition could be a consequence of this finding.
Syntheses of 1.BETA.-Methylcarbapenems Bearing 5-Methyl-4-hydroxypyrrolidinone.
作者:Do Kyu Pyun、Bong Jin Kim、Hee Jung Jung、Jae Hak Kim、Jin Soo Lee、Won Koo Lee、Cheol Hae Lee
DOI:10.1248/cpb.50.415
日期:——
A new series of 1β-methylcarbapenems 1a—d bearing 5-methyl-4-mercaptopyrrolidinone rings has been prepared and evaluated for in vitro antibacterial activity and pharmacokinetic parameters. Most compounds showed excellent antibacterial activity and high stability to dehydropeptidase-1. We have synthesized optically active 5-methyl-4-hydroxypyrrolidinones from enantiomerically pure aziridine esters.