Synthesis of 4,5-dihydroisoxazole derivatives of maleopimaric acid by 1,3-dipolar cycloaddition reaction between its allyl derivatives and aromatic nitrile oxides.

While searching for pharmacologically active compounds among 4,5-dihydrooxazole derivatives of maleopimaric acid, we studied for the first time the reaction between allyl-substituted maleopimaric acid derivatives and aromatic nitrile oxides that were generated from oximes by oxidation with sodium hypochlorite with or without ultrasonication of the biphasic system. The reaction occurred under mild conditions and regiospecifically provided 4,5-dihydroisoxazol-5-ylmethyl derivatives of maleopimaric acid in 77-99% yields. [ABSTRACT FROM AUTHOR]