1-(tert-butylthio)-1,2-hydrazinedicarboxylic acid derivatives. New reagents for the introduction of the S-tert-butylthio group into cysteine and cysteine derivatives.

The sterically hindered tert-butyl thiol reacts smoothly with azodicarboxylic acid derivatives only upon addition of catalytic amounts of sodium alcoholate, yielding crystalline and analytically well characterized 1-(tert-butylthio)-1,2-hydrazinedicarboxylic acid derivatives. These sulfur-activated reagents were found to be stable on storage and well suited as tert-butylthio carriers for the introduction of this thiol-protecting group on cysteine, cysteine derivatives and cysteine peptides; the related compounds are obtained in high yields.