Synthesis and reactions of α-thioformyl dipeptides, possible biogenetic precursors of penicillin

Abstract

Thioformyl dipeptides (II) have been synthesised by various routes and the existence of these unstable compounds has been verified by trapping experiments. At room temperature the thioaldehydes polymerise readily and at lower temperatures the thioenol forms are stabilised. When thioenolisation is prevented by the presence of an α-methyl substituent as in (XX), polymerisation is the only observable reaction. Cyclisation to β-lactam derivatives on a preparative scale has not been observed.