Oxidorhenium(V) complexes with L-histidine and pyranosides.

The reaction of the oxidorhenium(V) precursor [ReOCl(3)(PPh(3))(2)] with the proteinogenic amino acid L-histidine (L-hisH) and the glycosides methyl alpha-D-mannopyranoside (Me-alpha-D-Manp) and methyl beta-D-ribopyranoside (Me-beta-D-Ribp) in methanol/triethylamine yielded the crystalline compounds [ReO(L-his)(Me-alpha-D-Manp2,3H(-2))] x 2MeOH (1) and [ReO(L-his)(Me-beta-D-Ribp3,4H(-2))] x (1/2)MeOH (2). The mixed-ligand complexes based on the Re(V)O moiety were characterised by single-crystal X-ray diffraction, NMR spectroscopy, elemental analysis and mass spectrometry. Both complexes are hydrolytically stable over prolonged periods of time and are accessible also by a purely aqueous route by replacing the rhenium(V) precursor with a perrhenate/reductant couple.