Origin of slow conformer conversion of triostin A and interaction ability with nucleic acid bases.

The n.m.r. pattern of triostin A in weakly polar solvents was explained by the presence of two symmetrical conformers. Its S-benzyl derivative still shows the n.m.r. pattern of two conformers, while des-N-tetramethyltriostin A, which lacks the N-methyl groups, gives one conformer. Therefore the slow interconversion of two conformers arises from the cis-trans isomerization of the N-methyl peptide bonds, but not from the reversal of the chirality around the S-S bond. Only one of the two conformers of triostin A interacts with adenosine and guanosine derivatives. Des-N-tetramethyltriostin A can also interact with the purine nucleosides, but more preferentially with the adenosine derivative.