Chemistry of terminalia species-VI: The constitution of tomentosic acid, a new triterpene carboxylic acid from terminalia tomentosa wight et arn

Abstract

From the heartwood of T. tomentosa Wight et Arn, β-sitosterol, oleanolic acid (VI, R=R₁=H), arjunolic acid (I) and barringtogenol (IV) were isolated and in addition a new tetrahydroxy triterpene mono-carboxylic acid, now named Tomentosic acid. The triacetylmethyl tomentosate was oxidized to the corresponding ketone (XV) which could be reduced by forced Wolff-Kishner method to give methyl arjunolate (III). The above ketone also suffered isomerization in presence of alkali to give an α,β-unsaturated ketone (XVI). Further, during lactonization, the acid gives a trihydroxy anhydrolactone (X). The triacetylmethyl ester may be dehydrated using selenium dioxide to give methyldehydro arjunolate (XIX). From these reactions tomentosic acid is tentatively expressed as 2α,3β,19β,23-tetrahydroxy-olean-12-ene-28-oic acid (XII, R=H).