Sugars oximes

WOHL - WEYGAND Aldose degradation Degradation of sugar oximes via cyanohydrins by means of an acid chloride/pyridine (Wohl) or of... 

The conversion of nitroalkanes to ketoximes can be achieved by the reduction with Zn in acetic acid,112 or Fe in acetic acid.113 Nitroalkenes are direcdy reduced into saturated ketoximes by these reagents, which are precursors for ketones (see Section 6.1.4 Nef reaction). Reduction of 3-O-ace-ty lated sugar 1 -nitro-1 -alkenes with Zn in acetic acid gives the corresponding 2,3-unsaturated sugar oximes in high yield, which is a versatile route to 2,3-unsaturated sugar derivatives (Eq. 6.58).114... 

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

In 2000, Koos described a procedure for the reduction of the nitroolefin 140 to 5-deoxy sugar oxime 141 using tin(n) chloride as a reducing agent (Scheme 44).95... 

Scheme 30.—Proposed Mechanism for Photochemical Reactions of Glycosyl Azides and of Sugar Oximes.

Photolysis of sugar oximes produces iminolactones.178,179 These are the compounds proposed to arise from irradiation of glycosyl azides however, the mechanism leading to formation of iminolactones from these two starting-materials (azides and oximes) must be quite different (see Scheme 30). Photolysis of azides is considered to generate a nitrene, whereas photolysis of oximes produces an iminolactone that... 

Anomeric nitro sugars [35] are most efficiently prepared by ozonolysis of the N-glycosylnitrones obtained by reaction of aromatic aldehydes with the corresponding sugar oximes via the tautomeric N-glycosylhydroxylamines [36]... 

Wood sugar, AE80 Wood sugar oxime, AE93 Wurster s blue perchlorate, AS51... 

Another method for reductive amination of carbonyl compounds is based on the electroreduction of oximes in aqueous media. Thus, sugar oximes were reduced to their corresponding glycamines in good yields (Hg, KCl, acetate buffer). Similar reductions of oximes derived from furfural, salicylaldehyde, benzophenone and cyclohexanone have also been described, " but reports of preparative electrolyses in strictly aprotic media seem to be absent in the literature. 

The catalytic hydrogenation of sugar oximes in a neutral medium leads to a decrease in stereoselectivity112-114. 

In a number of instances (e.g., with steroids and sugars), oximes are formed prior to the silylation reaction [201, 202]. Muriatic o-pentafluorobenzylhydroxylamine has been used successfully to protect ketosteroids and increase the sensitivity of detection [203, 204]. It should be noted that oximes (under certain conditions) are converted quantitatively into the corresponding nitriles in a column [205]. In a number of instances it is expedient to use hydrazones to increase the stability of carbonyl compounds, including that of formaldehyde [206,207]... 

The sugar oximes needed for degradation by Wohl s method are best obtained by using hydroxylamine hydrochloride and pyridine.946... 

Cu2Cl2-py) have been used to convert aldose oximes into aldono-lactone oximes. Free sugar oximes gave products such as the D-gluco example (52) with a Z-confIguration, whereas 2,3 5,6-dl-O-Isopropylidene-D-mannose yields an E/ mixture (c.f. V0I.I6, p.lll... 

Synthesis of aldonohydroximino lactones via oxidations of sugar oximes has been reported The oxidations were effected by... 

When a sugar oxime in aqueous bicarbonate solution is treated with 2,4-dinitrofluorobenzene, degradation to the next lower sugar occurs with the liberation of hydrocyanic acid and 2,4-dinitrophenol 202). The degradation apparently is analogous, in its final stage, to the Wohl degradation. 

The sugars, probably in the free-aldehyde form (I), react 248) with hydroxylamine to give the sugar oximes (II or III) ... 

The products obtained upon acetylation of the sugar oximes depend not only on the temperature but also on the configuration of the sugar involved... 

Aminocyclitols have been obtained from sugar oxime derivatives by a radical cyclization procedure, as exemplified in Scheme 12. ... 

The hydrazone formed in this reaction usually crystallizes easily and is only sparingly soluble. A variation of this reaction is used in the chemistry of sugars. Oximes are formed analogously with hydroxylamine. 

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