Studies on the 5β,6β-epoxide opening in withanolides

Chlorinated withanolides from Withania somnifera

“…The known compounds were identified, by comparison of their NMR and MS data with those reported in the literature, as 6 α -chloro-5 β -hydroxywithaferin A ( 2 ) (Nittala et al, 1981); (22 R )-5 β -formyl-6 β ,27-dihydroxyl-1-oxo-4-norwith-24-enolide (Nittala and Lavie, 1982); withaferin A, 2,3-dihydrowithaferin A and 3-methoxy-2,3-dihydrowithaferin A (Pelletier et al, 1979); 2,3-didehydrosomnifericin (Choudhary et al, 1996); withanone (Gottlieb and Kirson, 1981); withanoside IV (Matsuda et al, 2001) and withanoside X (Zhao et al, 2002). Full assignments of NMR data for the known chlorinated withanolide 2 were listed in Table 1 because those values reported in the literature (Nittala et al, 1981) and, especially the assignments of its 13 C NMR data (C-4, 6, 10, 14, 17), need to be revised.…”

Withasteroids, a Growing Group of Naturally Occurring Steroidal Lactones

“…A concerted mechanism involving opening ofthe protonated epoxide, migration of the 18-methyl group to C-17 and formation of a 13,14-double bond by loss of H-14 which is outlined below appears to be a reasonable proposal. Methanolysis of the lactone ring and opening of the 5~,6~ epoxide to a trans-diequatorial chlorohydrin and diol in the presence of a 4~-hydroxy group are well-known steps (215 …”

Withanolides and related ergostane-type steroids

“…However, in a patent13' of 1986 (applied for in 1981) it is claimed that fermentation of withaferin A with the same microorganism afforded 14a-hydroxywithaferin A (169). It is quite possible that the correct structure of this compound is (170) and not Biotransformations of withaferin A were also induced by Arthrobacter ~i m p 1 e x . l ~~ Of the several derivatives thus obtained, only SP,6P-epoxy-27-hydroxy-1,4-dioxowitha-2,24dienolide was identified.…”