POTENTIAL INTERMEDIATE, (+ LSELANYL-3,3A-DIHYDRO-B-NOR-6,7A-SECOLYCORIN-5-ONE FOR SYNTHESIS OF THE AMARYLLIDACEAE ALKALOID LYCORINE - FORMAL AND TOTAL SYNTHESES OF (+/-)-LYCORINE/

Formal and total syntheses of the Amaryllidaceae alkaloid, (+/-)-lycor ine 1, were achieved by new synthetic routes via(+/-)-di-o-acetyl-3 ls elanyl-3,3a-dihydro-B-nor-6,7a-secolycorin-5-one 32. Namely, stereosel ective intramolecular Diels-Alder reaction of triene ester 5 afforded, in good yield, the cis-lactone 6, which was converted into beta(stere ochemical)-hydroxy-gamma-lactam 23. Oxidation of silyl ether 24 with m -chloroperbenzoic acid gave only beta-(tert-butyldimethylsiloxy)-alpha -epoxide 25, the stereostructure of which was determined by its X-ray crystallographic analysis. Payne rearrangement of compound 25 and succ essive acetylation furnished (stereochemical)-acetoxy-beta(stereochemi cal-epoxy gamma-lactam 29, which was transformed into (+/-)-lycorine 1 by construction of the B ring. Formal total synthesis of (+/-)-lycori ne 1 is also described.