Factors Influencing the Acid Lability of Substituted Arylsulphonyl Arginine Protecting Groups

Abstract

Abstract The kinetics of hydrolysis of new, NG-protected 2,4,6-triisopropylbenzene-sulphonyl (6). 4-methoxy-3,5-di-tert-butylbenzenesulphonyl (12) and phenanthrene-3-sulphonyl (17) Fmoc derivatives of L-arginine (1) in comparison with commercially available Fmoc-Arg(Mtr)-OH (Mtr = 4-methoxy-2,3,6-trimethyl-benzenesulphonyl (2)) are studies. The acid lability 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 of extended derealization does not appreciably increase the acid lability.