Diastereofacial selectivity in reduction of chiral tetramic acids
摘要:
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.
An improved process for the preparation of statine, the phenyl analog of statine, the cyclohexyl analog of statine and derivatives thereof is described, as well as other valuable intermediates used in the process.
A novel Wittig reaction of oxazolidinones: Stereospecific synthesis of N-BOC-(3S,4S)-Statine and N-BOC-(3S,4S)-AHPPA
作者:G.Vidyasagar Reddy、G.Venkat Rao、D.S. Iyengar
DOI:10.1016/s0040-4039(98)02409-5
日期:1999.1
Stereospecific synthesis of N-BOC-(3S,4S)-Statine and N-BOC-(3S,4S)-AHPPA is achieved via a novelWittigreaction of oxazolidinones in an efficient manner.
An improved process for the preparation of statine, the phenyl analog of statine, the cyclohexyl analog of statine and derivatives thereof is described, as well as other valuable intermediates used in the process.
The Stereoselective Synthesis of<i>threo</i>-3-Hydroxy-4-amino Acids
作者:Tsutomu Katsuki、Masaru Yamaguchi
DOI:10.1246/bcsj.49.3287
日期:1976.11
Two threo-3-hydroxy-4-amino acids, dl-4-amino-3-hydroxy-6-methylheptanoic acid (1) and dl-4-amino-3-hydroxy-2-methyl-5-(3-pyridyl)pentanoic acid (2), the optically active forms of which had been isolated by the acid hydrolysis of some antibiotics, were synthesized stereoselectively from l-leucine and Dl-3-(3-pyridyl)alanine respectively through 2-pyrrolidinone intermediates.