FACTORS INFLUENCING THE ACID LABILITY OF SUBSTITUTED ARYLSULFONYL ARGININE PROTECTING GROUPS

The kinetics of hydrolysis of new N-G-protected 2,4,6-triisopropylbenz ene-sulphonyl (6), 4-methoxy-3,5-di-tert-butylbenzenesulphonyl (12) an d phenanthrene-3-sulphonyl (17) Fmoc derivatives of L-arginine (1) in comparison with commercially available Fmoc-Arg(Mtr)-OH (Mtr = 4-metho xy-2,3,6-trimethyl-benzenesulphonyl (2)) are studies. The acid labilit y of the arylsulphonyl group is decreasing as follows Mtr > Tip > Mtbs > Phen. The effect of electron-donating alkyl groups as substituents in increasing the acid lability of the arylsulphonyl residue seems to be in the order of methyl > isopropyl > tert-butyl, while the effect o f extended delocalization does not appreciably increase the acid labil ity.