Synthesis of triterpenoid-based 1,2,4-trioxolanes and 1,2,4-dioxazolidines by ozonolysis of allobetulin derivatives

Abstract

Oxidation of allobetulin derivatives with ozone results in good isolated yields of 1,2,4-trioxolanes and stable 1,2,4-dioxazolidines. Individual 3R,5R and 3S,5S diastereoisomers of allobetulin secondary ozonides were isolated and their structures confirmed by X-ray crystallographic analysis. Remarkable diastereoselectivity with formation of only the (3S,5S)-configured peroxides was observed during the oxidation of 1,5-di-O-methoxyoximinoallobetulin to dioxazolidines.