Diastereoselective additions of organolithium and organomagnesium reagents to the C=N bond of a chiral, cyclic nitrone derived from erythrulose

The reaction of the 3,4-O-isopropylidene-L-(S)-erythrulose with hydroxylamine, followed by treatment of the resulting mixture of (E)- and (Z)-oximes with acetone and an acid catalyst, afforded two crystalline chiral compounds. Through X-ray diffraction analysis, these products were identified as a double acetonide derived from the (E)-oxime and a cyclic nitrone derived from the (Z)-oxime. The additions of organolithium and organomagnesium reagents to the C=N bond of the nitrone were found to be diastereoselective. The addition products are useful intermediates for die preparation of alpha,alpha-disubstituted alpha-aminoacids and other nitrogen-containing compounds in enantiopure form. (C) 1998 Elsevier Science Ltd. All rights reserved.