Chemistry of Terminalia species—IX: The structure of methyl anhydro tomentosate

Abstract

Methyl triacetyltomentosate by loss of water (1 mole) with POCl₃-pyridine yields methyl anhydrotomentosate which is not identical with methyl dehydroarjunolate. The anhydro compound yields a molecule of formaldehyde in OsO₄-Pb(OAc)₄ oxidation, establishing an exocyclic double bond, probably situated at C-20 through a methyl shift. It suffers facile catalytic reduction to give methyl dihydroanhydrotomentosate which resembles methyl asiatate in m.p., m.m.p., and lactonization but a comparison of their IR spectra reveals that probably inversion at C-19 has taken place during the Wagner-Meerwein methyl rearrangement.