Stereo- and Regioselective Synthesis of O-Mannosyl Glycan Containing Matriglycan and a Part of Tandem Ribitol Phosphate

We herein successfully synthesized two pivotal structures of O-mannosyl glycan: (1) the matriglycan-repeating tetrasaccharide Xylα1-3GlcAβ1-3Xylα1-3GlcAβ and (2) the link between matriglycan and a part of tandem ribitol phosphate, Xylα1-3GlcAβ1-4Xylβ1-4Rbo, in a regio- and stereocontrolled manner. The disaccharide unit with the α-linkage of xylose was obtained by adopting the conformational fixation of the xylopyranoside ring and a specific solvation system of diastereoselective solubility.

Sinapic acid derivatives from the seeds of Raphanus nussatirus L

A new disulfide glycoside, raphthioglucoside (1), and a new sinapic acid derivative, sinapic acid 5-hydroxymethylfurfural ester (2), together with sinapic acid (3) have been isolated from the seeds of Raphanus nussatirus L. The structures of compounds 1-3 were determined based on chemical analysis and spectroscopic methods (UV, 1D and 2D NMR, HRFABMS, HREIMS and elemental analysis).

Synthesis of α-series ganglioside GM1α containing C20-sphingosine

A synthesis of alpha-series ganglioside GM1alpha (III(6)Neu5AcGgOse4Cer) containing C20-sphingosine(d20:1) is described. Glycosylation of 2-(trimethylsilyl)ethyl 2,3,6-tri-O-benzyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside with the glucosamine donor ethyl 3-O-acetyl-2-deoxy-4,6-O-[(4-methoxyphenyl)methylene]-2-phthalimido-1-thio-beta-D-glucopyranoside furnished a beta-(1-->4)-linked trisaccharide. Reductive cleavage of the p-methoxybenzylidene group followed by intramolecular inversion of its triflate afforded the desired trisaccharide, which was transformed into a trisaccharide acceptor via removal of the phthaloyl and O-acetyl groups followed by N-acetylation. A tetrasaccharide acceptor was obtained by glycosylation of the trisaccharide acceptor with dodecyl 2,3,4,6-tetra-O-benzoyl-1-thio-beta-D-galactopyranoside, followed by removal of the p-methoxybenzyl group. Coupling of the tetrasaccharide acceptor with ethyl (methyl 4,7,8,9-tetra-O-acetyl-3,5-dideoxy-1-thio-5-trichloroacetamido-D-glycero-D-galacto-2-nonulopyranosid)onate and subsequent radical reduction gave the desired GM1alpha saccharide derivative, which was coupled with (2S,3R,4E)-2-azido-3-O-benzoyl-4-eicosene-1,3-diol after conversion into the imidate.