Triterpenoid Chemistry. VIII. : Stereospecific Reactions of Triterpenoid 1, 3-Glycol Monotosylates and Ketotosylates

Abstract

The reactions of 1, 3-glycol monotosylates of the configurations A-D with base and LAH were discussed. On reaction with t-butoxide, A and D (cis relationship between-OH and -CH₂OTs) gave oxetanes E and F respectively, while B and C (trans relationship between these groups) gave the same seco-aldehyde G. On LAH reduction, in addition to the above reaction (oxetane formation from A and D, seco-alcohol formation from B and C), two further reactions took place ; a) S-O fission (formation of the glycols A-D), and b) C-O fission (formation of the deoxy-compounds H and I), for the latter reaction the cyclic intermediate (K-M) were proposed. The monotosylate of B did not give deoxy-compound. The corresponding keto-tosylate (N and O), when treated with lithium aluminum hydride firstly gave 3β-alcohols (A and C) which are further reduced as above ; the fact which therefore opened a way to yield deoxy-compound (I) from type B glycol (B→N→I).