Proton magnetic resonance spectra of benzylidene derivatives of deoxysugars in the presence of the shift reagent Eu(DPM)

Some difficulties are often encountered when studying the conformation of saccharides by means of p.m.r. spectroscopy: the spectra are rather complex so that coupling constants and chemical shifts of the particular protons cannot be distinguished. The introduction of certain complexes of lanthanides possessing paramagnetic pro­ perties, so-called "shift reagents", into this field was of great importance. Pioneer papers [1,2] reported that substantial downfield shifts were observed in the p.m.r. spectrum of cholesterol in the presence of pyridine—Eu(DPM)3 complex, or upfield shifts [3] due to Pr(DPM)3 as a shift reagent. The shift reagent technique has also been extended to some derivatives of saccharides [4—6]. This paper refers to p.m.r. spectra of 4,6-benzylidene-2-deoxy-^-methylgulopyranoside (I) and 4,6-benzylidene-3-deoxy-a-methyl-D-mannopyranoside (II) recorded in the presence of Eu(DPM)3 at various temperatures. The goal of this paper was to separate the overlapping signals and to get information on the convenience of Eu(DPM) 3 in conformation determination of saccharides.