tert-Butyl group as thiol protection in peptide synthesis

Article abstract of DOI:10.1021/jo00322a024

S-tert-Butylcysteine was obtained by a new method. A number of its N-protected derivatives and esters were synthesized. Syntheses of several peptides containing tert-butyl and acetamidomethyl or benzyl thioethers of cysteine were carried out. The tert-butyl group was removed from the thiol group of peptides by treatment with (2-nitrophenyl)sulfenyl chloride (NpsCl). The S-(2-nitrophenyl)sulfenyl derivatives so obtained were converted either into cysteine by reduction or into cystine derivatives by disproportionation. Owing to the mild deprotection conditions and the great stability of the S-tert-butyl group, the other protecting groups, particularly those of the thiols, could be easily removed from a variety of combinations.