Long-range spin-spin interactions in the 13C-n.m.r. spectra of the nickel(II) complex of the Schiff base of (S)-N-benzylproline (2-benzoylphenyl)amide and glycine. Quantum-chemical calculations and possible donation of electron density from the π-system of the benzyl group to nickel

Long-range [nJ(13C, 13C), nJ(15N, 15N) and nJ(15N, 13C)] interactions in the 13C-n.m.r. spectra of CDCl3 solutions of selectively labeled nickel(II) complexes of the Schiff base derived from (S)-N-benzylproline (2-benzoylphenyl)amide and glycine provide experimental evidence for the necessity of the donation of electron density from the π-system of the benzyl ring to the nickel orbitals. No such interactions were observed in (2H)DMSO solutions, where the complex exists in a different conformation

Syntheses, X-ray, MSn, NMR and CD structure determination of nickel(II) complexes of Schiff bases of (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide and aromatic alpha-amino acids

A preparative procedure for the synthesis of an important chiral synthon of side-chain protected tyrosine was developed and optimised for the minimisation of nickel salts waste. While preparing a similar side-chain protected tryptophan synthon, an unexpected low stability was found of the Boc-protective group of the tryptophan aromatic nitrogen during purification on silica gel. X-ray crystal structure determination, tandem mass spectrometry (MS/MS) and NMR were applied for the elucidation of the structures Of the prepared complexes and by-products. Stereochemistry of products of alpha-methylation of the complexes was assessed using a model tyrosine-derived compound. (C) 2008 Elsevier Ltd. All rights reserved