STEREOSELECTIVE SYNTHESIS OF CYCLIC DIPEPTIDE HYDROXYALKYL ISOSTERES VIA METALATED N,N-DIALKYLCARBAMATE 2-ALKENYL ESTERS

Potential protease inhibitors are formed stereoselectively by a reaction sequence that begins with the conversion of N-protected alpha-amino aldehydes with the homoenolate reagent 1. The lactones 2 thus formed may be coupled with alpha-amino acid amides by a new variation of the Weinreb method in which dialkylaluminum amides are used as ring-opening agents. In this way for diastereomers of the compounds 3 belonging to the PSI-Phe[CHOHCH progroup are formed. R = CF3CO, Cb = C(C = O)NiPr2, Bn = PhCH2.