O-Methylation glycosides

CAN-mediated radical addition of acetylacetone to glycal (142) affords O-methyl glycoside (143) (eq. 4.50). 

CD Q a o Methyl glycoside of 2-C-benzyl-3-keto-L-Z xo-hexulosonic acid lactone Ci4HieO m)... 

The acid used in the Fischer glycoside synthesis was originally HCl (which made the kinetic data reproducible only with difficulty, as in methanol HCl is slowly consumed to form methyl chloride). Nowadays, ion-exchange resins are used preparatively, whilst the data on 4- and 5-O-methylated glycosides were obtained with camphor sulfonic acid. 

Zanetta J-P, Timmerman P, and Leroy Y (1999a) Gas-liquid chromatography of heptafluorobutyrate derivatives of the O-methyl glycosides on capillary columns a method for the quantitative determination of the monosaccharide composition of glycoproteins and glycoli-pids. Glycobiology 9 255-266. 

The synthesis of all the methyl mono-O-acetyl- - and - -D-xylo-pyranosides has been achieved by unimolecular acetylation of methyl mono-O-benzyl-D-xylopyranosides, followed by chromatographic fractionation and debenzylation. The three methyl di-O-acetyl-o -D-xylopyranosides were also obtained. Separation by liquid chromatography of the mixtures obtained by acetylation of a tri-O-methyl fraction from partial methylation of methyl ot-D-glucopyranoside gave all possible mono-O-acetyl-tri-O-methyl glycosides. Acetylation of D-xylose with acetic anhydride in... 

The present work involves the study of methyl glycosides and O-isopropylidene ketals of various isomeric deoxy sugars by mass spectrometry. Several of the compounds selected for the present study have free hydroxyl groups, and interpretation of their mass spectra shows the scope of the study of these and related deoxy sugar derivatives by mass spectrometry without prior substitution of all hydroxyl groups. Some of the candidates (compounds 4, 7, 8 and 10) are structurally related to biologically-derived deoxy sugars. 

All of the mono-O-methylated hexopyranosides are sweet, with only a trace of bitterness. The bitterness is more pronounced in the methyl glycoside derivatives, and this was attributed to the presence of two lipophilic centers (—OMe) in the methyl glycosides and only one in the a,a-trehalose analogs. ... 

Glycosyl-residue compositions were determined by GC-CIMS analysis of the per-O-trimethylsilylated methyl glycosides [23] separated on a fused-silicaDB-1 capillary column. The identity of each peak was confirmed by CIMS on a HP-5989 MS Engine (Hewlett-Packard). 

Bhaskar and Loganathan96 described O-peracetylation of monosaccharides, disaccharides, and methyl glycosides (94) with acetic anhydride under catalysis by acid zeolites. From the panel of zeolites tested (HY, HEMT, HZSM-5, HZSM-12, HZSM-22, and H-beta), the large-pore zeolite H-beta provided the best yields of the fully acetylated sugars, most of them being over 85% and up to 99%, with the pyranose forms 95 accounting for 66-100% of the reaction products (Scheme 22). 

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