The conversion of turraeanthin and turraeanthin A into simple meliacins by a route involving an oxidative rearrangement of probable biogenetic importance

Abstract

Treatment of turraeanthin (VIII) and its 3α-epimer, turraeanthin A (IX), with sodium periodate in aqueous dioxan containing a trace of perchloric acid, followed by dehydration of the products with toluene-p-sulphonic acid in benzene, has afforded tetranortirucallane triterpenoids, (XIX), (XX), and (XXIII), containing a β-substituted furyl side-chain. Epoxidation of these tetranortriterpenoids followed by rearrangement by treatment with boron trifluoride–ether complex in benzene has provided a pathway to the simplest meliacins [e.g.(XXIX)].