Amino Acids and Peptides. XLVII. Facile Synthesis of Flavacol, Deoxymuta-aspergillic Acid and Optically Active Deoxyaspergillic Acid from Dipeptidyl Aldehydes

2(1H)-Pyrazinone ring-containing natural products, flavacol, deoxymuta-aspergillic acid and finally optically active deoxyaspergillic acid, were easily synthesized by a newly developed procedure for preparation of 2(1H)-pyrazinone derivatives from dipeptidyl aldehyde hydrochlorides. The absolute configuration of natural deoxyaspergillic acid was synthetically determined as S.