Synthesis and Intramolecular Cyclization of 2,3-Seco-Lupane Triterpenoids with an Ethylketone Fragment

A 1-cyano-2,3-secolupane derivative with an ethylketone fragment was synthesized from 2-hydroxyoximodihydrobetulonic acid methyl ester via a Grignard reaction followed by a Beckmann rearrangement and was used further to prepare α -bromo-substituted diastereomers. Nitrile-anionic cyclization of the ethylketone and α -bromo isomers produced cyclic derivatives with an alkenenitrile and an α,β -unsaturated ketone in ring A, respectively. The obtained compounds did not exhibit cytotoxic activity according to biological screening data.