TRIPHENYLTIN(IV) DERIVATIVES OF N-ACETYL AMINO-ACIDS, N-ACETYL DIPEPTIDES AND TRIPEPTIDES - PREPARATION, NMR INVESTIGATIONS AND NMR SPECTROSCOPIC RESOLUTION OF THE ENANTIOMERIC COMPOSITION

Triphenyltin(IV) derivatives of N-acetyl amino acids (la-g) and N-acet yl di- (2a-f) or tripeptides (3) mostly in the (L)- and the racemic (D L)-form have been prepared from bis(triphenyltin)oxide and the appropr iate N-acetyl amino acid or N-acetyl peptide using various dehydrating agents. The compounds were characterized by NMR spectroscopy and elem ental analysis. These compounds were studied at different concentratio ns and temperatures, revealing a strong self-association tendency. NMR investigations were undertaken in order to highlight preferred confor mations of the peptide derivatives due to possible strong intramolecul ar associations between tin and nucleophilic donor atoms of the peptid e moiety in weakly polar solvents. No preferred conformation was found which was in accordance with the underivatized peptides. The enantiom eric composition was determined by means of H-1 NMR spectroscopy using (-)-quinine hydrochloride and S-(-)-1-phenylethylamine as chiral solv ating agents.