Use of Pd/sepiolite systems as hydrogenation catalysts. II. Hydrogenolysis of N-blocked amino acids and dipeptides by hydrogen transfer

Abstract

We have carried out the deprotecting of various N-protected amino acids and dipeptides by subjecting them to hydrogen transfer with several palladium catalysts supported on different solids. The hydrogen donor itself has been used "insitu" to reduce the corresponding Pd salt on the support. We have also analyzed the effect of various factors on the deprotecting rate for Z-glycine. Such factors include the procedure used in synthesizing the catalysts ("insitu" or by conventional reduction), the type of support, hydrogen donor, promoting effect of alkaline hydroxides, type of reactor (closed or open), and magnetic or ultrasonic agitation. We have found that the ease of adsorption of the protected amino groups (Z—NH—) is fundamental in accounting for the order of deprotecting rates found. We have compared the activity of new catalysts in the deprotecting process with that of a commercial one containing 10% Pd over carbon, supplied by Fluka (ref. 75990).