Diastereoselective alkylation of aromatic enamidone functionality in isoindole series: A convenient route to chiral aza-analogues of senkyunolide-C

Chiral aza-analogues (2a) and (2b) of Senkyunolide-E were efficiently synth esized in a four-step sequence (72 and 70% overall yields respectively) fro m the commercially available phthalic anhydride and (S)-(-)-alpha-phenyleth ylamine. The key step consisted in the 1,2-addition of Grignard reagents on to enamidone type compounds (8) and (9). These latters were regioselectivel y obtained from the parent omega-alkynyl-omega-carbinol lactams (6) and (7) by a Meyer-Schuster rearrangement.