Hydrate of 2,3:4,5-di-O-isopropylidene-β-D-arabino-hexos-2-ulo-2,6-pyranose as new crystalline reagent in the preparation of Amadori derived peptides

Abstract

Abstract:We established, that crystalline hydrate of 2,3:4,5-di-O-isopropylidene-ß-D-arabino-hexos-2-ulo-2,6-pyranose is a new, convenient and stable reagent for solid phase synthesis of peptide derived Amadori products. The structure of the title compound was studied by X-ray analysis, NMR spectroscopy, and high resolution ESI-MS. The crystal structure indicated the existence of two symmetry-independent molecules that were not connected with hydrogen bonds. A comparison with previously reported 2,3:4,5-di-O-isopropylidene-ß-Dfructopyranose revealed, that these two compounds are isostructural.

Direct glucosone-based synthesis and HILIC-ESI-MS/MS characterization of N-terminal fructosylated valine and valylhistidine for validation of enzymatic HbA1c assays in the diagnosis of diabetes mellitus

“…As further purification step as well as to clearly characterize the iprGlu, it was converted into its hydrate form, following a procedure from Stefanowicz and co-workers [31]. A twofold amount of water was added to the oily crude iprGlu.…”

“…The synthesis was conducted following a procedure from the group of Hoffmann [18], and after purification by column chromatography, a yield of 72% (7.5 mmol batch size) iprGlu was obtained. Due to ambiguous analytical data of iprGlu, which is present as the aldehyde as well as its stable hydrate from, it was converted completely into its stable hydrate form under the addition of water, which subsequently crystallized as white solid [31]. Despite the fact that hydrates of carbonyls, the so-called gem-diols, are generally not stable and can therefore not be isolated, there are some exceptions [39][40][41].…”

“…Despite the fact that hydrates of carbonyls, the so-called gem-diols, are generally not stable and can therefore not be isolated, there are some exceptions [39][40][41]. In this case, the crystalline gem-diol structure was studied by Stefanowicz et al [31], who also demonstrated that the hydrate converts back to the aldehyde in solution, therefore not hampering further reactions of the aldehyde group. Complete conversion of iprGlu into its hydrate form was confirmed by NMR and IR spectroscopy (see ESM).…”