Biogenetic syntheses of kopsijasminilam and deoxykopsijasminilam

The hexacyclic ketoester 7, derived from cyclization of racemic minovincine (6), was reduced to two C-19 epimeric alcohols 8 and 9. Stereoelectronical ly controlled fragmentations of corresponding O-sulfonyl derivatives provid ed, respectively, the hexacyclic enamine 14 and, after oxidation of the ole fin 16, the pentacyclic lactam 17 with a brigehead double bond. Formation o f a carbamate, introduction of a second double bond at C-16, and conjugate reductive hydroxylation at C-20, or hydrogenation, gave the title products.