Cyclopropanation of Carbon-Carbon Double Bonds in Ring D of Ergot Alkaloids

Abstract

-Some ergot alkaloid derivatives containing a double bond in ring D have been reacted with diazomethane/palladium diacetate reagent to result in formation of a fused cyclopropane ring. This procedure proved to be generally applicable for cyclopropanation of Ergot alkaloids.Some years ago thorough investigation has been carried out to achieve cyclopropanation of the double bond located in ring D of a C-nor-ergoline derivative (1) in order to perform the total synthesis of the racemic form of cycloclavine (2) which is the only known alkaloid containing a fused cyclopropane ring. This goal has been reached by using diazomethane/diethyl ether reagent in the presence of palladium diacetate.1 To the best of our knowledge, this was the first example for formation of a fused cyclopropane ring in alkaloids.