NMR Analysis of Synthetic Oligosaccharide Fragments of the OSP of E. coli O-148

Eunice Kennedy Shriver National Institute Of Child Health & Human Development

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Abstract

The NMR data measured for synthetic 5-methoxycarbonylpentyl glycosides of tetrasaccharide (4-mer), octasaccharide (8-mer), and dodecasaccharide (12-mer) components of the OSP of E. coli O148 have been prepared for publication, with the H-1 chemical shifts, C-13 chemical shifts, H1/H-1 coupling constants, and 1J C-1,H-1 heteronuclear coupling constants of the 4-mer, 8-mer, and 12-mer summarized. In the course of validating the structures of synthetic BBGL-2 variants by 1D and 2D NMR methods, we have now made detailed H-1 and C-13 NMR assignments for four of these structures;namely, 1,2-di-O-oleoyl-, 1-O-oleoyl-2-O-palmitoyl-, 1-O-palmitoyl-2-O-oleoyl-, and 1,2-O-palmitoyl-3-O-alpha-D-galactopyranosyl-sn-glycerols. Interpretation of the C-13=O chemical shifts of the four galactosyl diglycerides has led to a set of rules that describe the dependence of these C-13 shifts on fatty acid type, and substituent position on the glycerol moiety. The rules are useful for NMR analysis of the mixtures of products that result from acylation reactions of imperfect regiospecificity. The NMR data for the four diglyceride analogs have been prepared for publication by constructing three tables, comprising 1H chemical shifts, 13C chemical shifts, and geminal and vicinal H-1/H-1 and 1J C-1,H-1 coupling constants.