Structural investigation of lac resin. Part X. Structure and stereochemistry of methyl laccolate γ-lactone and its epimer
The structure and stereochemistry of two lactones obtained by esterification of the gum resulting from the alkaline fission of shellac are discussed. They are the 8-epimers of 9,13-epoxy-10β-hydroxycedrane-12,15-dioic acid 12,10-lactone 15-methyl ester and appear to have been formed from shellolic acid by intramolecular addition of the hydroxymethyl group to the double bond of the αβ-unsaturated carbonyl system. Methyl esters of laksholic and 2-epi-laksholic acids, previously described as gums, have been obtained crystalline and characterised as derivatives.