Syntheses and interfacial behaviour of neoglycolipid analogues of glycosyl ceramides

Four glycosyl ceramides analogues having D-galactose or 2-acetamido-2-deoxy-D-glucose moieties linked to enantiomeric lipids have been synthesised to study their interfacial behaviour at the air \ water interface. The lipid chains were prepared in two steps by opening 1,2-epoxyhexadecane using Jacobsen kinetic hydrolytic resolution (KHR) followed by an azidosilylation reaction of the diol so obtained. Glycosylation reactions were realised either with 2,3,4,6-tetra-O-benzoyl-alpha -D-galactopyranosyl trichloroacetimidate or 1,3,4,6-tetra-O-acetyl-2-allyloxycarbonylamino-2-deoxy-beta -D-glucopyranose as donors and (2R)- or (2S)-2-azidohexadecanol derivatives as acceptors. Transformation of the azido glycosides into N-acylated products was done by a modified Staudinger reaction in the presence of fatty acyl chlorides. The four neoglycolipids are able to form a condensed monolayer at the air \ water interface; their pi -A isotherm diagrams are similar to that described for the natural glycosyl ceramides. The detailed analysis of the isotherms, taking into account the chirality of the lipid chains, allowed to determine the contribution of the different parts of the molecule under the monolayer packing. (C) 2001 Elsevier Science Ltd. All rights reserved.