A glycosylation protocol based on activation of glycosyl 2-pyridyl sulfones with samarium triflate.

[reaction--see text] Reaction of glycosyl 2-pridyl sulfones (e.g.,2) with alcohols and samarium(III) triflate affords glycosides in moderate to excellent yields. Benzylated sulfones can be activated in preference to their benzoylated counterparts, and the methodology has been used to prepare di- and trisaccharides containing both furanose and pyranose residues. Thioglycosides do not react under these conditions, and the sulfones are inert to the N-iodosuccinimide/silver triflate promoter system commonly used to activate thioglycosides. This selectivity allowed the efficient preparation of oligosaccharides via orthogonal glycosylation protocols.

Effect of supplemental chromium on antibody responses of newly arrived feeder calves to vaccines and ovalbumin.

Two trials were conducted to investigate the effects of supplemental chromium (Cr) from organic sources (Cr chelate and high Cr yeast) on antibody responses of newly arrived feeder calves following vaccination with infectious bovine rhinotracheitis (IBR), para-influenza-3 (PI3), bovine respiratory syncytial virus (BRSV), bovine viral diarrhea (BVD) and Pasteurella haemolytica and ovalbumin (OVA). Using cross bred steer calves purchased at sales in Ontario, vaccines and OVA were given on d 0 and 21 after arrival in the feedlot. Immune responses of calves were measured as serum specific antibody titres against all antigens on d 0 and 28 or d 35. The anti-OVA antibody responses (trial 2) were further investigated by measuring antibody concentrations of calves weekly until d 55 after arrival in the feedlot. Supplemental Cr (0.14 ppm) from an amino acid-chelated source had no effect on antibody responses to IBR, P13 and BRSV, but enhanced (P < 0.05) antibody titres of calves in response to the BVD vaccine on d 28 or d 35. Supplemental Cr from Cr yeast had no effect on antibody titres of calves to any vaccines. Chromium from both sources (trial 1 and 2) had no effect on antibody responses of calves following vaccination with P. haemolytica. However, supplemental Cr (0.75 ppm) from Cr yeast enhanced (P < 0.05) serum antibody responses of calves to OVA during the primary response (d 14) and secondary response (d 35) following immunization. These data confirmed our previous finding that supplemental Cr can enhance humoral immune response of market-transit stressed calves, but its enhancement on vaccine efficacy was antigen-dependent and variable.