Design and facile synthesis of neoglycolipids as lactosylceramide mimetics and their transformation into glycoliposomes

Abstract

Neoglycolipids composed of disaccharide glycoside and phospholipid were designed and prepared as mimetics of lactosylceramide. The lactosyl- and N-acetyllactosaminyl-phospholipids (Lac-DPPA and LacNAc-DPPA) were enzymatically synthesized from lactose and LacNAc respectively by cellulase-mediated condensation with 1,6-hexanediol, followed by conjugation of the resulting glycosides and dipalmitoyl-phosphatidyl choline (DPPC) mediated by Streptomyces phospholipase D. Alternatively, allyl β-lactoside was ozonolyzed to give an aldehyde, which was condensed with dipalmytoyl phosphatidyl ethanolamine to afford a second type of glycolipid (Lac-DPPE). NMR spectroscopy indicated that the neoglycolipids behave differently in different solvent systems. X-ray diffraction clearly showed that multilamellar vesicles (MLVs) of LacDPPE and Lac-DPPA-MLV are in the bilayer gel phase at 20°C, whereas those of Lac-DPPE-MLV were in the lamellar liquid-crystalline phase at 50°C. Differential scanning calorimetry showed that Lac-DPPE-MLV had complex thermotropic behavior depending on the incubation conditions. After a long incubation at 10°C, endothermic transitions are observed at 39.6, 42.3°C, and 42.9°C. These neoglycolipids have the ability to trap calcein, a chelating derivative of fluorescein, in MLVs and showed specific binding to lectin in plate assays using fluorescently labeled compounds.