A. Dondoni, G. Fantin, M. Fogagnolo
Mar 1, 1990
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Journal
Journal of Organic Chemistry
Abstract
The stereochemistry and synthetic utility of the addition of 2-(trimethylsilyl)thiazole (2-TST, 1) to various N-protected α-amino aldehydes is described. The reactions of 1 with n-Boc-L-serinal acetonide (2) and N-Boc-L-threoninal acetonide (3) are essentially anti diastereoselective (ds=85-90%) in agreement with the Felkin-Anh model for asymmetric induction, whereas the reactions with O-benzyl-NH-Boc-L-serinal (4) and NH-Boc-L-phenylalaninal (5) are syn diastereoselective (ds=80%). The reversal of diastereoselectivity is interpreted on the basis of a proton-bridged cyclic Cram model for asymmetric induction