An efficient synthesis of the four mono methylated isomers of (+)-catechin including the major metabolites and of some dimethylated and trimethylated analogues through selective protection of the catechol ring

The four monomethylated isomers of (+)-catechin in positions 3', 4', 5 and 7, two dimethylated derivatives, the 5,7-dimethylcatechin and the 3',4'-dimethylcatechin and two trimethylated isomers of (+)-catechin in positions 3',5,7 and 4', 5, 7 were synthesized by a new method based on successive and selective protections of the various phenol functions present on (+)-catechin. The key step was the selective protection of the catechol ring with dichlorodiphenylmethane and di-tert-butyldichlorosilane.