STUDIES ON ANALOGUES OF HUPERZINE A FOR TREATMENT OF SENILE DEMENTIAⅡSYNTHESIS OF ANALOGUES OF (±)-DINOR HUPERZINE A

Huperzhe A(1),isolated from the Chinese folk medicine Huperzia Serrata, is a potent and reversible inhibitor of acetylcholinesterase. Clinical trials have confirmed that huperzine Ais effective in the treatment of senile dementia,In this paper we report the synthesis of analogues 7and 8 retaining structurally the basic carbon skeleton of huperzine A. he β-keto ester 2 reacted with acrolein to perform in situ Michael-Aldol condensations and toafford the axial and equatorial hydroxy compounds 9 and 10,separated by silica gel columnchromatography.The hydroxy compounds were converted into mesylates 11and 12,respectively.Byrefluxing the mesylate in acetic acid with sodium malonate at 130℃,elimination product 13 wasformed only from axial mesylate 11 and SN₂ reaction occurred with equatorial mesylates 12 to giveaxial acetate 14.Intermediate 13 was finally transformed into analogue 7 according to the totalsynthesis route,involving Wittig olefination of ketone, hydrolysis of ester,modified Curtiusrearrangement and TMSI- promoted deprotection,Similarly,analogue 8 was synthesized fromintermediate 23, which was prepared from compound 13 by catalytic hydrogenation. Antiacetylcholinesterase activities of analogues 7 and 8 were found to be much lower than that ofhuperzine A.