Carbon-linked glycosides

A. Dondoni, A. Marra, and M. G. Zampolli, Synthesis of all carbon linked glycoside clusters round benzene scaffold via Sonogashira-Heck-Cassar cross coupling of iodobenzenes with ethynyl C-glycosides, Synlett, 11 (2002) 1850-1854. 

Structures in which the linking glycosidic oxygen is replaced by -CH2- may be named by use of the replacement prefix carba- (c/. 2-Carb-34.2) for emphasis of homomorphic relationships. The oxygen replaced is given the locant of the carbon atom to which it is attached in the residue with the lower roman numeral (cited as superscript) (cf 2-Carb-37.2), with suffix a1. 

A set of ten carbon-linked (1 6) dimers was prepared in this way, starting from the C-glyco-syl formaldehydes 33 and 42-47 and the phosphonium salts 34 and 48 [41] (O Scheme 9). This route requires, however, the use of the thermodynamically more stable aldehydes a-C-glucosyl precursor 44 will provide, for example, the corresponding -C-dimer by isomerization under the basic conditions of the Wittig reaction. An exception is the use of aldehyde 50 obtained selectively from the corresponding thiazolyl a-C-glycoside 49, provid-... 

Paulsen s group has transformed the protected streptosyl chloride (or bromide) (521 RS = Ph,H) into dihydrostreptosylstreptidine (522) and related pseudo-disaccharides. ° ° The 2,3-0-benzylidene derivatives (521 R R = Ph,H) yielded a-linked glycosides of L-streptose preferentially, whereas the 2,3-carbonates (521 R R = O) gave / -linked glycosides e.g. with cyclohexanol and l,2,3,4-tetra-0-acetyl-)5-D-glucopyranose). ° This work culminated in the synthesis of D-streptobiosamine (523) and its L-enantiomer (a disaccharide unit of streptomycin) by a route that involved condensation of methyl a-o(or L)-strepto-side 3 -(trimethylene dithioacetal) with the nitrosyl chloride adduct of 3,4,6-tri-O-acetyl-D-(or L)-glucal. ... 

Steroidal alcohols when condensed with 2,3,4-tri-O-ben l-a-L-rhamnopyranosyl or tetra-O-benzyl-a-D-mannopyranosyl chloride in the absence of catalyst or solvent afford good to excellent yields of a-linked glycosides (a,p ratios 10 1). Another report describes the use of cobalt carbonate for activating the condensation of substituted glycosyl halides and steroidal alcohols. ... 

In classical sophorolipids known since 1961, a sophorose unit is linked glycosidically to a hydroxyl fatty acid residue, as shown in Fig. 2. The C17 carbon atom of the 17-hydroxy-octadecenoic acid moiety has been determined to be 5-configurated. 

The relationship between the Haworth formulae and the two chair forms for the more common pyranose sugars is illustrated in the following formulae. In drawing conformational formulae the direction of the bonds is determined by the tetrahedral valencies of the carbon atoms and the glycosidic carbon links in the Ci conformation must be drawn as in (CXXX) and not as in (CXXXI). 

Nucleosides are compounds formed when a base is linked to a sugar via a gly-cosidic bond (Figure 11.10). Glycosidic bonds by definition involve the carbonyl carbon atom of the sugar, which in cyclic structures is joined to the ring... 

Disaccharides contain a glycosidic acelal bond between the anomeric carbon of one sugar and an -OH group at any position on the other sugar. A glycosidic bond between Cl of the first sugar and the -OH at C4 of the second sugar is particularly common. Such a bond is called a 1—>4 link. 

Fischer projections and, 977-978 glycosides and, 989-990 l- 4 links in, 997-998 origin of name. 973 photosynthesis of, 973-974 see also Aldose, Monosaccharide vaccines from, 1004-1005 Carbon, ground-state electron configuration of, 6... 

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