A Modified Total Synthesis of (±)-Lycorine

Abstract

A modified total synthesis of lycorine w a s accomplished starting from the lactam-ester ( 5 ) .Selective reduction of the lactam carbonyl of 2 , followed by cyclization gave 5-oxolycorene (4).Epoxidation of 4 -gave stereoselectively the a-epoxide ( 2 ) .Repeated application of Sharpless method to convert epoxide into allylic alcohol and acetylation of the product gave diacetyl 5-oxolycorine (1_91.Lithium aluminium hydride reduction of 2 gave (2)-lycorine.Recently, we have accomplished the first total synthesis of Rmaryllidaceae alkaloids lycorine (1) and zephyranthine (2)In that synthesis, the double bond on ring C of the tetracyclic six-membered lactam (3) was functionalized in a stereoselective manner elaborating these alkaloids.The tetracyclic five-membered lactam (4) with a carbonyl group on ring D is also an attractive synthetic intermediate for lycorine-type alkaloids, since it has a potency introducing functional groups not only on ring C but also on ring D. This communication presents the stereocontrolled transformation of the lactarn (4) into (t)-lycorine.