Alkyl monoglucosides contain one D-glucose unit. The ring structures are typical of D-glucose units. Both five and six member rings that include one oxygen atom as the heteroatom are related to furan or pyran systems. Alkyl D-glucosides with five-member rings are therefore called alkyl d-glucofuranosides, and those with six-member rings, alkyl D-glucopyranosides.
All D-glucose units show an acetal function whose carbon atom is the only one to be linked to two oxygen atoms. This is called an anomeric carbon atom or anomeric center. The so-called glycosidic bond with the alkyl residue, as well as the bond with the oxygen atom of the saccharide ring, originate from the anomeric carbon atom. For orientation in the carbon chain, the carbon atoms of the D-glucose units are numbered continuously (C-1 to C-6) starting with the anomeric carbon atom. The oxygen atoms are numbered according to their position at the chain (O-1 to O-6). The anomeric carbon atom is asymmetrically substituted and can therefore assume two different configurations. The resulting stereoisomers are called anomers and are distinguished by the prefix α or β. According to the nomenclature conventions anomers show that one of the two possible configurations whose glycosidic bond points to the right in the Fischer projection formulas of glucosides. Precisely the opposite is true of the anomers.
In the nomenclature of carbohydrate chemistry, the name of an alkyl monoglucoside is composed as follows: Designation of the alkyl residue, designation of the anomeric configuration, the syllable “D-gluc,” designation of the cyclic form, and addition of the ending “oside.” Since chemical reactions in saccharides usually take place at the anomeric carbon atom or the oxygen atoms of the primary or secondary hydroxyl groups, the configuration of the asymmetrical carbon atoms does not normally change, except in the anomeric center. In this respect, the nomenclature for alkyl glucosides is very practical, since the syllable “D-gluc” of the parent saccharide D-glucose is retained in the event of many common types of reactions and the chemical modifications can be described by suffixes.
Although the systematics of saccharide nomenclature can be developed better according to the Fischer projection formulas, the Haworth formulas with cyclic representation of the carbon chain are generally preferred as structural formulas for saccharides. The Haworth projections give a better spatial impression of the molecular structure of the D-glucose units and are preferred in this treatise. In the Haworth formulas, the hydrogen atoms linked to the saccharide ring are often not presented.
Post time: Jun-09-2021