From Nitro-sugars

5 From Nitro-sugars. - The 2-acetamido-2-deoxy-p-D-galactopyrano-sylamine 25 was obtained by addition of benzimidazole to a 2-nitro-galactal derivative (see Chapter 10).  

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The nitronate anion derived from nitro sugar 82, available from glucopyranoside 1 using standard methods, condenses with aldehyde 33 to afford adduct 83. Reduction with diimide of the ii-olefin, produced in low yield by radical elimination of the nitroaldol, and removal of the... 

Radical additions have been particularly successful here and, for example, cyanoalkyl glycosides have been prepared from nitro-sugars and acrylonitriles in the presence of tr i-r -buty It in hydride. Radical equivalents of homo-enolate additions have... 

From nitro-sugars. - iV-Acetyl-lactosamine 30 and N-acetyl-cpt-lactosamine 31 were obtained as a manno-nch epimeric mixture on ozonolysis of the 2-acetamido-l-nitro-derivatives 29, obtained from 3-0-(p-D-galactosyl)-D-arabinose 28 (Scheme 8). The / a /io-isomer 32 could be obtained in 15% yield from 28), by direct crystallization. Treatment of the product mixture with aqueous ammonia gave a g/uco-rich mixture from which the g/oco-isomer 30 could be crystallized (32% yield from 28). Similar procedures applied to L-arabinose led to 2-acetamido-2-deoxy-L-mannose and - glucose... 

Oxidation is a general method for the preparation of nitro sugars from other sugar derivatives, as amino or azido sugars and sugar oximes. 

Amino sugars can usually be oxidized to the corresponding nitro sugars using m-chloroperbenzoic acid (MCPBA).6 Thus, Kobertz et al. synthesized nitro sugar 2 from amino sugar 1 by treatment with MCPBA in 1,2-dichloroethane under reflux (Scheme l).7... 

Intramolecular Henry reactions of nitro sugars are usually diastereo-selective sometimes a single isomer results from an epimeric mixture, on account of the reversivility of the Henry reaction, which allows equilibration through open chain intermediates.49 A recent example involving the D-glucose derived nitro acid ester 26 is shown in Scheme 22. 

A simple synthesis of a 7-membered aza sugar from the unsaturated aldehyde 4 was proposed by Moutel.8 The same aldehyde 4 was used in the synthesis of modified aza sugars such as 5 (Fig. 2) 9 An interesting approach to polyhydroxylated 7-membered branched aza sugars (e.g. 8) was proposed by Estevez.10 Nitro sugar 6 underwent the... 

T. Sakakibara and R. Sudoh, Stereoselective synthesis of the thermodynamically less stable manno-isomers from a nitro sugar, Carbohydr. Res., 50 (1976) 191-196. 

FIGURE 1.4 Nucleosides of DNA and RNA. The nucleosides are each composed of a base and a 5-membered sugar. The bond from the sugar to the base involves a carbon-to-nitro-gen bond. The base is, in fact, a base because of the nitrogen atoms, which can be pro-tonated. 

This radical adds to the nitronate ion derived from 6-nitro sugar 246. Tin-hydride mediated denitration leads to an a-(1 6) C-linked disaccharide 248. 

MacDonald and Fischer prepared D- fluco-hexodialdose (27) by two different methods. By use of the Nef reaction, 6-deoxy-l,2-0-isopropyli-dene-6-nitro-n-glucose (26) was converted into the dialdose (27), which was isolated from the aqueous solution as its insoluble, crystalline bis-(diethyl dithioacetal) (in 48% yield, after recrystallization). It is of interest to note that the starting material (26) is one of the two isomeric 6-deoxy-6-nitro sugars which Grosheintz and Fischer prepared from 1,2-0-iso-propylidene-a-D-x2/lo-pentodialdo-l, 4-furanose (7). Thus, the synthesis discussed here is an ascent from a pentodialdose to a hexodialdose. 

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