Reaction of Methyl (2-Methylidene)-3-oxolup-20(29)-en-28-oate with Dimethyl Trimethylsilyl Phosphite

A method of phosphorylation of pentacyclic triterpenoids derivatives containing an α,β-unsaturated carbonyl fragment in the ring A was described by the example of the reaction of methyl (2-methylidene)-3-oxolup-20(29)-en-28-oate with dimethyl trimethylsilyl phosphite. Methyl 2-dimethoxyphosphorylmethyl-3-oxolup-20(29)-en-28-oate was obtained as two epimers in a 2: 1 ratio in a 70% yield.