Hydrogenolysis sulfur containing peptides

A -Benzyloxycarbonyl groups, catalytic hydrogenolysis in sulfur-containing peptides, 59, 166... 

The main drawback in the catalytic hydrogenolysis of Z-protected peptide derivatives is caused by the presence of sulfur-containing amino acid residues (Cys, Pen, or Met) due to catalyst poisoning. Attempts to overcome these restrictions by addition of either tertiary basesf or boron trifluoride-diethyl ether complext to the hydrogenation mixture were of limited usefulness. More efficient appears to be the use of liquid ammonia (at —33°C) as the solvent to prevent poisoning of the Pd/C catalyst.f °l... 

The H2/Pd hydrogenolysis system for the removal of the Z group from peptides is limited to sulfur-free peptides. In order to overcome this limitation, Meienhofer successfully conducted hydrogenolysis in liquid ammonia as a solvent to remove the Z group from Cys- or Met-containing peptides.As shown in Scheme 23, protected somatostatin was prepared in a stepwise manner starting from H-Cys(tBu)-OtBu. 

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