Synthetic studies on chaksine

Abstract

This thesis is concerned with the studies in the synthesis of a monoterpenoid alkaloid, chaksine. Ethyl 2-n~butyl-4-bromoacetoacetate (11) was treated with sodium azide to give ethyl 2-n-butyl-4-azidoacetoacetate (12), Catalytic hydrogenation of (12) in presence of hydrochloric acid followed by the reaction of the hydrogenation product (13) with potassium cyanate afforded 4-(1'- carbethoxypenty1)-2-imidazolone (14) or 4-(1'-carboxypentyl)- 2-imidazolone (15) depending on reaction condition. 4-(1'-carbethoxymethyl)-2-imidazolone (25) was also prepared starting from ethyl 4-bromoacetoacetate (23a) following the same series of reaction as described for the compound (14). Ethyl 2-[4'-methy1-5'-(2"-tetrahydropyranyloxy1)pentyl] acetoacetate (20) was prepared from the reaction of ethyl acetoacetate and 5-bromo-2-methyl-1-(2'-tetrahydropyranyloxyl)pentane (19). Removal of the 3,4- dihydropyran protecting group from (20) yielded ethyl 2-(4'-methyl—5'-hydroxypentyl)acetoacetate (21). The compound (21) was also prepared directly by the reaction of ethylacetoacetate with 5-bromo-2-methyl- pentanol (18), The compound (21) was then subjected to bromination to give (22a) followed by the treatment of (22a) with sodium azide to yield ethyl 2-(4'-methyl-5'-hydroxypentyl)-4-azidoacetoacetate (22b) .