Cyclopropanation of betulin and its diacetate with dihalocarbenes

Reactions of betulin, its diacetate, and 17-acetoxy-28-norlupan-3-one with dichlorocarbene generated from chloroform follow the [1 + 2]-cycloaddition pattern leading to the corresponding adducts in moderate to quantitative yield. In the reaction with betulin, [1 + 2]-cycloaddition is accompanied by dichlorocarbene attack on the primary hydroxy group to give the corresponding halogen derivative and formate. The addition of dichlorocarbene to betulin is strictly stereoselective, while the reaction with betulin diacetate affords a mixture of two diastereoisomers at a ratio of 95 : 5. The reaction of betulin diacetate with dibromocarbene yields dibromocyclopropane derivative which can be converted into the the corresponding diol.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1511–1516.Original Russian Text Copyright © 2004 by Komissarova, Belenkova, Shitikova, Spirikhin, Yunusov.