An Improved Synthetic Method for dl-Griseofulvin and Its 2′-S-Analogue
17 September 2002 (online)
An improved synthetic method for dl-giseofulvin (4) and its 2′-S-analogue 8 has been developed. 7-Chloro-4,6-dimethoxy-2-[5-methoxy-1-methylthio-3-oxohexylidene]-3 (2H)-benzofuranone (7), prepared by reaction of the corresponding 3 (2H) -benzofuranone with 1,1-bis(methylthio)-5-methoxy-1-hexen-3-one (6), undergoes stereoselective intramolecular cyclization when treated with activated alumina in refluxing diethyl ether. The product, the 2′-S-analogue of dl-griseofulvin 8, is converted to dl-griseofulvin (4) in good yield.