Glucose with nitrous acid

Deamination of the hexosamine molecule occurs on heating it with alkali,205 and determination of the ammonia evolved is the basis of one quantitative method for the determination of 2-amino-2-deoxy-D-glucose.206 Deamination of 2-amino-2-deoxy-D-glucose with nitrous acid leads to the formation of 2,5-anhydro-D-mannose ( chitose ), which can be isolated as the crystalline diphenylhydrazone.207 Reduction of 2,5-anhydro-o-man-... 

Anhydro-D-mannose, produced from 2-amino-2-deoxy-D-glucose with nitrous acid, has been converted by standard procedures Into the dlhydrofuran (31) and hence Into the Isomers (32) and (33) of... 

More-specific methods are available for identifying and quantitating the typical, amino sugar component of heparin (and some heparan sulfate species), namely, 2-deoxy-2-sulfoamino-D-glucose. Most of these methods are based on conversion of these residues into 2,5-anhydro-D-mannose by deamination with nitrous acid (see Section VIII,2). The 2,5-anhydro-D-mannose residues may be determined either colorimetrically,52-54 or fluorimetrically.55... 

In analogy with the deamination of aminocyclohexanes,17-21 it has been found that the deamination, with nitrous acid, of 2-amino-2-deoxyaldohexoses in which the amino group has an equatorial orientation leads to 2,5-anhydrohexoses, as exemplified by the deamination of 2-amino-2-deoxy-D-glucose (10) to 2,5-anhydro-D-mannose22-25 (11). 

An original approach to the analysis of amino sugars has been proposed, based on their reaction with nitrous acid and subsequent reduction of the products with borohydride.564 By this procedure, 2-amino-2-deoxy-D-glucose and 2-amino-2-deoxy-D-galactose are converted into 2,5-anhydrohexitols, whereas 2-amino-2-deoxy-D-mannose yields D-glucitol. This mixture is readily separated after trimethyl-silylation. 

As acetamido groups do not react with nitrous acid under the usual conditions, it was possible to identify 2-acetamido-2-deoxy-D-glucose residues in heparin after deamination,244 and their distribution was... 

Whitesides and coworkers have carried out a comparison of enzymic and chemical routes to CTP, GTP and UTP on a 10-gram scale. They concluded that CTP and GTP were best made enzymically, and UTP by reaction of CTP with nitrous acid. The triphosphates were then employed for the enzymic synthesis of UDP-Glucose, UDP-Glucuronic acid, and GDP-Mannose.i94 Cytidine diphosphate sugars have been prepared from the 3,6-dideoxyhexoses paratose and abequose,193 and all four nucleoside diphosphate sugars of 6-sulpho-a-D-quinovose have been synthesized for studies of sulpholipid biosynthesis in chloroplasts.196 The stable analogue (138) of CMP-KDO has been prepared by a triester approach, but was only a weak inhibitor of KDO incorporation into lipopolysaccharides.197 A reference to acetylated forms of UDPGlc is mentioned in Chapter 7. 

The nitrous acid deamination of 2-amino-2-deoxy-D-mannose (8), in the favored conformation, the amino group ofwhich is axially attached, leads, in contrast, uniquely to D-glucose,15 characterized, after oxidation by nitric acid, as D-glucaric acid (9). This result has also been verified by direct crystallization of the D-glucose and by assay with D-glucose oxidase.44"... 

This reaction has been compared81 with the nitrous acid deamination of 2-amino-2-deoxy-D-glucose attack by a bromonium ion could lead to an intermediate, alkyl-iodonium cation (2-C-I-Br) , which would decompose through nucleophilic attack by 0-5, which is antiparallel to the leaving group at C-2. 

---