A LIGHT-INITIATED PROCESS FOR RAPID DEBENZYLATION OF CARBOHYDRATES

During the synthesis of several disaccharides to be used in the preparation of analogues of the anticancer agent mithramycin (1), difficulties (slow and sometimes incomplete reaction) were encountered with catalytic hydrogenolysis, the traditional method for removal of benzyl protecting groups. Although these difficulties, which have been known for some time to accompany occasionally the hydrogenolysis of benzyl ethers, 1,2 were not insurmountable, they created sufficient inconvenience to stimulate interest in other debenzylation reactions. A number of alternatives to catalytic hydrogenolysis have been reported. These include reaction with molecular bromine, 3 sodium in liquid ammonia, 1boron trifluoride etherate, 4 iodotrimethylsilane (followed by hydrolysis), 5 ferric chloride, 6 ruthenium tetraoxide, 7 and ozone. 8 Other known methods involve electrochemical oxidation, 9 catalytic transfer hydrogenation 2,10,11and homogeneous electron transfer12. © 1990, American Chemical Society. All rights reserved.