Transformation of ω-anhydro-20-hydroxyecdysone diacetonide into 7,8α-dihydroponasterone a and its acetonides

Abstract

7,8α-Dihydroponasterone A and its mono-and diacetonides were synthesized via catalytic hydrogenation of ω-anhydro-20-hydroxyecdysone 2,3 : 20,22-diacetonide over Pd/C in methanol in the presence of sodium methoxide.Difficultly accessible ecdysteroids and their analogs can be synthesized via transformation of ω-anhydro-20-hydroxyecdysone diacetonide which is a mixture of 24(25)-and 25(26)-dehydroponasterones A (I) formed by dehydration of 20-hydroxyecdisone diacetonide [1,2]. For instance, inokosterone was obtained by reduction of I with sodium tetrahydridoborate [3], whereas ozonolysis of I followed by trifluoromethylation of ω-carbonyl compounds gave 27,27,27-trifluoro-20-hydroxyecdysone [4].We recently reported on a new procedure for the reduction of the C 7 =C 8 double bond in ecdysteroids by catalytic hydrogenation over Pd/C in alkaline methanol solution [5]. Following this procedure, ponasterone A