Synthesis of Lewis X trisaccharide analogues in which glucose and rhamnose replace N-acetylglucosamine and fucose, respectively

Indirect synthetic route to α-l-fucosides via highly stereoselective construction of α-l-galactosides followed by C6-deoxygenation

We developed an indirect synthetic method for α-l-fucosides. Based on the fact that l-fucose is 6-deoxy-l-galactose, our strategy consists of the stereoselective construction of α-l-galactoside and its conversion to α-l-fucoside via C6-deoxygenation. The formation of α-l-galactoside is strongly directed using 4,6-O-di-tert-butylsilylene(DTBS)-protected l-galactosyl donors. The DTBS-directed α-l-galactosylation showed broad substrate applicability along with excellent coupling yield and α-selectivity. In the C6-deoxygenation of α-l-galactosides, the Barton-McCombie reaction facilitated the conversion to l-fucosides with good yield. To demonstrate the applicability of our method, we synthesized naturally occurring α-l-fucosides.

Synthesis of 4" manipulated Lewis X trisaccharide analogues

Three analogues of the Le^x trisaccharide antigen (β-D-Galp(1→4)[α-L-Fucp(1→3)]-D-GlcNAcp) in which the galactosyl residue is modified at O-4 as a methyloxy, deoxychloro or deoxyfluoro, were synthesized. We first report the preparation of the modified 4-OMe, 4-Cl and 4-F trichloroacetimidate galactosyl donors and then report their use in the glycosylation of an N-acetylglucosamine glycosyl acceptor. Thus, we observed that the reactivity of these donors towards the BF₃·OEt₂-promoted glycosylation at O-4 of the N-acetylglucosamine glycosyl acceptors followed the ranking 4-F > 4-OAc ≈ 4-OMe > 4-Cl. The resulting disaccharides were deprotected at O-3 of the glucosamine residue and fucosylated, giving access to the desired protected Le^x analogues. One-step global deprotection (Na/NH₃) of the protected 4”-methoxy analogue, and two-step deprotections (removal of a p-methoxybenzyl with DDQ, then Zemplén deacylation) of the 4”-deoxychloro and 4”-deoxyfluoro protected Le^x analogues gave the desired compounds in good yields.

Altered detection of molecules associated with leukocyte traffic in HUVECs derived from newborns with a strong family history of myocardial infarction

Atherosclerosis is a chronic inflammatory disease. As such, recruitment of immune cells is a significant event. Tightly controlled signaling molecules regulate leukocyte adhesion and migration to the tissues. The aim of this study was to determine if human umbilical vein endothelial cells (HUVECs) derived from healthy newborns with a strong family history of myocardial infarction (FHMI) showed variations in the presence of molecules related with leukocyte traffic and migration, in comparison to control healthy newborns. For this purpose, we evaluated the labeling of sialic acid containing glycoproteins, tight junction claudins and the cytoskeleton, using lectin- and immunocytochemistry in HUVECs from individuals with and without a strong FHMI. Our results show important differences in the labeling of alpha-2,3 or alpha-2,6 sialic acid-containing glycoconjugates, a disarrangement of actin filaments secondary to the absence of cytoplasmic claudin-5 immunopositivity and an increase in the binding of FHMI HUVECs to CD3+ Jurkat cells. It is possible that these differences relate to a predisposition for early appearance of atherosclerotic lesions.