Disclosed herein is a method for synthesizing terpenoid compounds, as well as compositions comprising terpenoids and methods for their use. In one aspect the process is represented by the scheme wherein G is X is and R1, R2 and R3 independently are selected from H, acyl, lower alkyl and aralkyl; and Y is —O—, —S— or —NH—, and R4 is selected from H, acyl, lower alkyl and aralkyl.