Adducts of rhodium(II) tetraacylates with methionine and its derivatives: H-1 and C-13 nuclear magnetic resonance spectroscopy and chiral recognition

作者：Glaszczka Rafal; Jazwinski Jaroslaw^*; Kamienski Bohdan; Kaminska Monika

来源：Tetrahedron: Asymmetry , 2010, 21(19): 2346-2355.

DOI：10.1016/j.tetasy.2010.08.010

Complexation of rhodium(II) dimeric tetraacylates: tetraacetate Rh2AcO4, tetratrifluoroacetate Rh(2)TFA(4), and (S)-Mosher's acid salt Rh(2)MTPA(4) with both enantiomerically pure and racemic methionine and its derivatives: hydrochloric salt of methionine, hydrochloric salt of methionine methyl ester, N-formyl methionine, N-phthaloyl methionine, N-phthaloyl methyl ester of methionine, and methyl ester of N,N-dimethylmethionine has been investigated by means of H-1 and C-13 nuclear magnetic resonance (H-1 and C-13 NMR) and absorption electronic spectroscopy in the visible range. Complexation processes were investigated in D2O or CDCl3 solutions, depending on the ligands' and rhodium salts' solubilities. Some supporting measurements were performed in the solid phase, using C-13 and N-15 CPMAS NMR techniques.
All ligands investigated form 1:1 and 1:2 adducts in the solution, depending on the rhodium salt to ligand molar ratios. The complexation site in the ligands (S atom) was deduced on the basis of the NMR parameter adduct formation shift (Delta delta = delta(adduct) -delta(ligand)) and calculated chemical shifts (DFT, NMR GIAO). In the cases of the Rh(2)TFA(4) and Rh(2)MTPA(4) adducts, decreasing the temperature within the range 220-254 K slowed down the ligand exchange and allowed us to observe the signals of all diastereoisomers in the H-1 and C-13 NMR spectra.

• 出版日期2010-10-7