Enantiopure N-protected α-amino glyoxals 1. Synthesis from α-amino acids and some condensation reactions with amines

A series of N-protected α-amino diazoketones has been prepared from L-amino acids and dipeptides and used as precursors in the synthesis of novel N-protected α-amino glyoxals via oxidation with distilled dimethyldioxirane (DMD) in acetone. The glyoxals have been converted, without purification, into enantiopure imines, pyrazines, quinoxalines, and pyrido[2,3-b]pyrazines via condensation with the appropriate amine or diamine. The molecular structure of the pyrido[2,3-b]pyrazine derived from N-Cbz-L-phenylalanine has been determined by X-ray analysis.