Hemiketals, nomenclature

Hemiketals, nomenclature, 122-123 Heparin, Maurice Stacey s work, 11 Histidine pyridoxol pathway, 305 H NMR spectra... 

The cyclic hemiacetal and hemiketal forms of monosaccharides are capable of reacting with an alcohol to form acetals and ketals (see Section 7.2). The acetal or ketal product is termed a glycoside, and the non-carbohydrate portion is referred to as an aglycone. In the nomenclature of glycosides we replace the suffix -ose in the sugar with -oside. Simple glycosides may be synthesized by treating an alcoholic solution of the monosaccharide with an acidic catalyst, but the reaction mixture usually then contains a mixture of products. This is an accepted problem with many carbohydrate reactions it is often difficult to carry out selective transformations because of their multifunctional nature. 

The nomenclature of the oxidized forms of AA is badly in need of revision. Not only is dehydroascorbic acid a long and cumbersome name, but it is also confusing in inferring that the compound is an acid. As is discussed later in this chapter, the principle structure is a bicyclic compound containing both lactone and hemiketal groups. Names such as ascorbitone or dehydroascorbitone would be better trivial representations. 

Formerly it was conventional to use the terms hemiacetal and acetal for compounds formed by reaction between aldehydes and alcohols. Similar reactions between ketones and alcohols gave rise to compounds called hemiketals and ketals. Current nomenclature uses hemiacetal and acetal for compounds derived from either an aldehyde or a ketone, but reserves hemiketal and ketal for those derived from ketones. In other words, the ketals are a subclass of the acetals and the... 

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