R. Galeazzi, G. Mobbili, M. Orena
Jan 15, 1996
Citations
0
Influential Citations
46
Citations
Journal
Tetrahedron
Abstract
The oxidative cyclisation of a series of either (S)-N-(2-alken-1-yl)-N-(1-phenyleth-1-yl)-acetoacetamides5a-d and methoxycarbonylacetamides 6a-b, performed by using Mn(OAc)3 · 2H2) and Cu(OAc)2 · H2O in acetic acid, has been examined. The reaction proceeds regioselectively through a 5-exo-mode, leading to 1,3,4-trisubstituted pyrrolidin-2-ones 7a-d,8a-d and 9a-b,10a-b as diastereomeric mixtures in about 2:1 ratio, which are easily separated by silica gel chromatography. The configuration of the pure diastereomers is assigned from 1H NMR data and confirmed by NOE experiments. The observed asymmetric induction has been explained on the basis of molecular mechanics calculations. This cyclisation constitutes a useful tool for the synthesis of biologically active amino acids containing the pyrrolidine ring in both enantiomerically pure forms, such as (R)- and (S)-3-pyrrolidineacetic acid, 1 and 2.