Abstract: Successive N-methylation of L-cystine (L-CYSSCY (1)) reverses the relative magnitudes of the vicinal coupling constants and chemical shifts of the anisochronous methylene hydrogens on passing from di-to tetramethylcystine. These pmr results indicate that the most stable staggered ethanic rotamer with anti sulfur and carboxylate residues for 1 is succeeded by the rotamer with anti sulfur and methylated ammonium groups. For the ...
