New Method to Prepare N-t-Butoxycarbonyl Derivatives and the Corresponding Sulfur Analogs from di-t-Butyl Dicarbonate or di-t-Butyl Dithiol Dicarbonates and Amino Acids

Di-t-butyl dicarbonate and one of its dithiol analogs, practical methods of preparation for which are given, react with amino-acid esters to form the N-t-butoxycarbonyl (t-BOC) derivatives and the thiol analogs in good yield under mild conditions. The thiol analogs are stable to acidic conditions, which rapidly remove the t-BOC group itself. t-Butyl trimethylsilyl carbonate forms a (CH3)3Si ether from a N-thiol-t-BOC serine methyl ester. The N-thiol-t-BOC group can be removed from the -NHCOSR (R = t-butyl) by heating with peroxide-acetic acid. Action of the dicarbonates described above has not been attended by racemization in the cases examined. The two dicarbonates may be useful as agents for selective blocking and deblocking of amino or other groups.