Neighboring group participation in epoxide ring cleavage in reactions of some 16α,17α-oxidosteroids with lithium hydroperoxide
2001; Elsevier BV; Volume: 57; Issue: 11 Linguagem: Inglês
10.1016/s0040-4020(01)00051-5
ISSN1464-5416
AutoresJacek W. Morzycki, Agnieszka Gryszkiewicz, Izabella Jastrzębska,
Tópico(s)Phytochemistry and Bioactive Compounds
ResumoIn order to work out a new approach to the synthesis of the potent anti-tumor saponin OSW-1 aglycone, 16α,17α-oxidosteroids were treated with acids, bases and lithium hydroperoxide. Acids caused Wagner–Meerwein type rearrangements irrespective of the side-chain structure. 16α,17α-Epoxides proved resistant to bases unless a 22-carbonyl group was present; in the case of 22-esters or 22-ketones the epoxide rings were cleaved with base and the corresponding allylic alcohols were formed. The epoxide ring cleavage of 16α,17α-oxido-22-ester with lithium hydroperoxide was followed by lactonization of the intermediate 16β,17α-dihydroxy acid. The saponin OSW-1 aglycone was obtained by reaction of the lactone with isoamyllithium.
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