SYNTHESIS OF CYCLIC ACYLATED ENAMINO ESTERS FROM ENOL LACTONES, 4-KETO AMIDES, AND 5-HYDROXY LACTAMS

Enol lactones react with an amine to give either a keto amide or a hyd roxy lactam under mild conditions. Subsequent dehydration with p-tolue nesulfonic acid (PTSA) gives a cyclic acylated enamino ester in good y ield (Tables 1 and 2, Schemes 2 and 4). The key prostaglandin analog p recursor 18 and the gly-gly dipeptide analogs 26a and 26b were prepare d using the reported conditions. Acetylation of the chloro hydroxy lac tam 31, prepared from the chloro enol lactones 29, followed by elimina tion of acetic acid gave the chloro acylated enamino esters 28.