Further studies on the use of multi-substituted benzenesulfonyl groups for protection of the guanidino function of arginine.

Various multi-substituted benzenesulfonyl protecting groups for the guanidino function of arginine, removable under mild conditions such as with trifluoroacetic acid (TFA)-thioanisole, were studied. Among them, the 4-methoxy-2, 6-dimethylbenzenesulfonyl (Mds) group, the 2, 3, 4, 5, 6-pentamethylbenzenesulfonyl (Pme) group, and the 4-methoxy-2, 3, 6-trimethylbenzenesulfonyl (Mtr) group were found to be useful. Both Mds and Pme show considerable resistance to TFA and, therefore, are suitable for procedures in which the intermediates are deprotected by TFA treatment, while Mtr is the most useful protecting group when TFA treatment is not necessary.