Quinoline alkaloids. Part 20. Synthesis of ptelefolone and O-methylribaline. Ring closure of epoxides of 3-prenylquinolones

Abstract

2-(1-Hydroxy-1-methylethyl)-6,8-dimethoxy-9-methyl-2,3-dihydrofuro[2,3-b]quindiolin-4(9H)-one (5a) and its 8-monomethoxy-analogue O-methylribaline (5d) were prepared from 3-prenylquinolones. Reaction of the N-methyl-4-quinolone (5a) with triphenyl phosphite dichloride gave ptelefolone (9) and the asymmetric synthesis of the alkaloid was explored. Ring closure of epoxides of 3-prenylquinolones in basic and non-basic media is discussed.