Methyl /-glycosides

Methyl glycosides of 2 deoxy sugars have been prepared by the acid catalyzed addition of methanol to unsaturated sugars known as glycals... 

The use of penodic acid oxidation m structure determination can be illustrated by a case m which a previously unknown methyl glycoside was obtained by the reaction of D arabmose with methanol and hydrogen chlonde The size of the nng was identified as five membered because only one mole of penodic acid was consumed per mole of glycoside and no formic acid was produced Were fhe nng six membered fwo moles of penodic acid would be required per mole of glycoside and one mole of formic acid would be produced... 

The mechanism for formation of the 3 methyl glycoside is shown The mechanism for for mation of the a isomer is the same except that methanol approaches the carbocation from the axial direction... 

FeCl3, CH2CI2, 2-3 min, 68% yield. Benzyl ethers are cleaved in 15-20 min under these conditions. Methyl glycosides, acetates and benzoates were not affected by this reagent. 

Phosphate esters of 2-deoxy D-galactose (2-deoxy-D-Zt/xo-hexose) have also been obtained (15). The 6-phosphate (12) was synthesized from the methyl glycoside (9) by condensing the latter with acetone the 3,4-... 

An attractive feature in this reaction is the possibility of direct substitution and formation of unblocked sugar derivatives containing one or more chlorodeoxy function in essentially two steps. Another facet is the formation of methyl 4,6-dichloro-4,6-dideoxy-hexosides from certain methyl glycosides in one step. Such compounds could be valuable intermediates in the synthesis of dideoxy and diamino sugars of biological importance. 

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. 

The widespread occurrence and biological significance of polyoxygenated carbocycles provided the impetus to apply RCM to sugar-derived dienes. Carbohydrate carbocyclization based on a sequence of Vasella reductive opening of iodo-substituted methyl glycosides [25], and RCM of the dienes available from the resulting unsaturated aldehydes, were used to prepare a series of natural compounds (Schemes 5-7). 

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). 

RG-n, Rhamnogalacturonan II Kdo, 3-deoxy-D-manno-octulosonic acid Dha, 3-deoxy-D-/yxo-heptulosaric acid aceric acid, 3-C- carboxy-5-deoxy-L-xylose TMS, per-0-trimethylsilylated methyl glycosides. 

The monosaccharide composition of all the samples was determined by GLC analysis of the trimethylsilyl methyl glycoside derivatives [1]. 

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