N-acetyllactosamine Derivatives Research Articles

A convenient synthesis of N-acetyllactosamine derivatives from lactal

In a thermal inverse-type hetero-Diels-Alder reaction of O-protected lactal 1 and bis(2,2,2-tri-chloroethyl) azodicarboxylate ( 2), the dihydrooxadiazine derivative 3 was obtained in a very high yield; transesterification with benzyl alcohol furnished the corresponding derivative 4. Treatment of 3 with methanol in the presence of BF 3·OEt 3 afforded the methyl lactoside derivatives 5 which, after transesterification with benzyl alcohol, then hydrogenolytic debenzylation and concomitant NN-cleavage with Raney nickel, and N-acetylation, furnished methyl O-(2,4,6-tri- O- tert-butyldimethylsilyl-β- d-galactopyranosyl)-(1 → 4)-2-acetamido-3,6-di- O- tert-butyldimethylsilyl-2-deoxy-β- d-glucopyranoside ( 7) in high yield. Desilylation of 4, then O-acetylation, methyl glycoside formation with methanol-BF 3·OEt 2, hydrogenolytic debenzylation, and NN-cleavage with Raney nickel, and N-acylation afforded methyl O-(2,3,4,6-tetra- O-acetyl-β- d-galactopyranosyl)-(1 → 4)-2-acetamido-3,6-di- O-acetyl-2-deoxy-β- d-glucopyranoside ( 10).

Binding characteristics of galactoside-binding lectin (galaptin) from human spleen.

Binding characteristics of human spleen soluble galactoside-binding protein (galaptin) were studied using simple galactosides, galactose-terminated disaccharides, cluster glycosides containing up to 6 terminal lactosyl residues, bovine serum albumin derivatives containing 7 to 40 lactosyl residues, desialylated serum glycoproteins, and glycopeptides derived thereof as inhibitors in a newly developed binding assay. In this assay, aminohexyl lactoside was attached to divinyl sulfone-activated Sepharose, which was then used to bind 125I-galaptin. Similarly derivatized Sepharose containing mannoside served as a control. The assay is sensitive, maintains linearity in the concentration range of 125I-galaptin tested, and has very low nonspecific binding. The following new findings were made. 1) All the alpha-D-galactopyranosides with non-sugar aglycon were better inhibitors than the corresponding beta-D-galactopyranoside. 2) The S-galactosides were better inhibitors than the corresponding O-galactosides, regardless of the anomeric configuration. 3) Many Gal beta 1-4- and Gal beta 1-3-linked disaccharides were tested. Although the galaptin did not appear to recognize N-acetylglucosamine as a monosaccharide, the presence of this sugar penultimate to galactose increased the binding affinity by as much as 500-fold, as was the case for N-acetyllactosamine. Of a particular importance is the presence of an equatorial 3-OH group on this sugar. We synthesized the 3-deoxy derivative of N-acetyllactosamine and found that it had 50-fold lower binding affinity compared to N-acetyllactosamine. 4) The binding sites of this lectin do not seem to be operating in a cooperative fashion, since synthetic lactose-containing divalent ligands with various inter-galactose distances did not increase the binding affinity significantly.

Poly N-acetyl lactosamine derivatives in branching morphogenesis: [formula omitted], Department of Pathology, University of Southampton, SOUTHAMPTON, England

Poly N-acetyl lactosamine derivatives in branching morphogenesis: [formula omitted], Department of Pathology, University of Southampton, SOUTHAMPTON, England