PREPARATIONS OF BOC-CYS(S-PYR)-OH AND Z-CYS(S-PYR)-OH AND THEIR APPLICATIONS IN ORTHOGONAL COUPLING OF UNPROTECTED PEPTIDE SEGMENTS

Boc-Cys(S-Pyr)-OH and Z-Cys(S-Pyr)-OH were prepared by addition of the ir cysteine derivatives to 3 equiv of 2,2'-dipyridyldisulfide in one p ortion. 2-Mercaptopyridine was removed by addition of 0.1 M Cu(NO3)(2) to the solution. Both derivatives are white solids and can be used to facilitate the formations of heterodisulfide bonds. Two methods of sy nthesizing peptides with N-terminal Cys(S-Pyr) were also provided. Two peptide thiocarboxylic acids H-Tyr-Ser-Ala-Glu-Leu-Val-SH and H-Tyr-S er-Ala-Glu-Leu-Gly-SH were prepared on the thioester benzhydryl resin with the cleavage condition of 1.0 M TFMSA/TFA instead of HE From the orthogonal couplings of these peptides with H-Cys(S-Pyr)-Tyr-Ser-Glu-L eu-Ala-NH2, both intramolecular acyl transfers finished at pH 7 at abo ut 15 to 20 min. The intermediate acyl disulfide peptide was collected by high-performance liquid chromatography and identified by liquid ch romatography-mass spectrometry. (C) Munksgaard 1998.