Optical rotatory dispersion and circular dichroism. Part LXIII. Unsaturated triterpene 28-carboxylic acids and related compounds

Abstract

Optical rotatory dispersion and circular dichroism curves have been measured for a large number of naturally occurring Δ-12 unsaturated triterpene acids. The results are compared with those for analogous saturated acids and for the corresponding unsaturated hydrocarbons, and are discussed in terms of the possible preferred conformation of the carboxy group. Triterpenoid acids of types (I) and (II) would appear to exist in solution with a preferred conformation in which the carboxy-group is syn-planar with the C(16)–C(17) bond.