Amadori products from model reactions of d-glucose with phosphatidyl ethanolamine—Independent synthesis and identification of 1-deoxy-1-(2-hydroxyethylamino)-d-fructose derivatives

Nonenzymatic glycosylation of aminophospholipids is supposed to play an important role for lipid oxidation in vivo. Investigations are reported on how the Amadori products 1-deoxy-1-[2-(1,2-ditetradecanoyl-sn-glycero-3-phosphooxy)ethylamino]-d-fructose (4) and 1-deoxy-1-[2-(1,2-dihexadecanoyl-sn-glycero-3-phosphooxy)ethylamino]-d-fructose (5) can be identified from model reactions of d-glucose and phosphatidyl ethanolamine. Independent syntheses and unequivocal structural characterization are given for the EZ-1-deoxy-1-(2-hydroxyethylamino)-d-fructose (3-methylbenzothiazolin-2-ylidene)hydrazone (12a,b) and the peracetylated EZ-1-deoxy-1-(2-hydroxyethylamino)-d-fructoseO-methyloxime (13a,b). Chromatographic and spectroscopic data for these 1-deoxy-1-(2-hydroxyethylamino)-d-fructose derivatives were established by either GLC-MS or HPLC with diode array detection (DAD). Phosphatidyl ethanolamine and d-glucose were incubated at 37 °C, pH 7.4, in neat buffer or ethanol-buffer mixtures for four weeks, and the phospholipid fraction was purified on a C18 solid-phase extraction column. The phosphatidic acid was cleaved with phospholipase D and the free 1-deoxy-1-(2-hydroxyethylamino)-d-fructose derivatized to give 12a,b or 13a,b, respectively. Both these derivatives could be identified from all incubations by GLC-MS and HPLC-DAD analyses, respectively. Formation of 4 and 5 is favored in ethanol-buffer reaction mixtures relative to those in buffer solution only.