chapter  13
20 Pages

Selective Hydrogenolysis of Benzyl and Carbobenzyloxy Protecting Groups for Hydroxyl and Amino Functions

WithLouis S. Seif, Kenneth M. Partyka, John E. Hengeveld

In synthesizing complex molecules, protected functional groups must be deblocked. Benzyl and carbobenzyloxy groups attached to oxygen or nitrogen are important protecting groups in many complex syntheses. The competitive catalytic debenzylation of N versus 0 and the hydrogenolysis of carbobenzyloxy groups in the presence of benzyloxime will be discussed.

Selective debenzylation studies will focus on the following examples: N-benzylcyclohexylamine, benzylcyclohexyl ether, dibenzyl-p-aminophenol, and 6-O-methyl-2‘-O-(benzyl)-3’-N-(benzyl)erythromycin A 9-O-(benzyl)oxime ammoniol iodide. In addition, carbobenzyloxy group hydrogenolysis in the presence of benzyloxime protecting groups will be illustrated utilizing the following example: 3’-de(dimethyl-amino)-6-O-methyl-3‘-[methyl(benzyloxycarbonyl)amino]-2’-O-(benzyloxy-carbonyl)erythromycin A 9-[O- (2-chlorobenzyl)oxime].