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 α‐amino aldehydes with the homoenolate reagent 1 . The lactones 2 thus formed may be coupled with α‐amino acid amides by a new variation of the Weinreb method in which dialkylaluminum amides are used as ring‐opening agents. In this way four diastereomers of the compounds 3 belonging to the Ψ‐Phe[CHOHCH] progroup are formed. RCF 3 CO, CbC(CO)N i Pr 2 , BnPhCH 2 .