Oxygen alditols

Aminomercuration aminoalditols The synthesis of the natural aza-alditol 1-deoxynojirimycin (4) from methyl a-D-glucopyranoside involves the reductive ring-opening (Zn) and reductive amination (NaBH3CN) of 1 to give 2 in 91% yield. Aminomercuration of 2 results mainly in the bromomercurial 3, which was converted into the aza-sugar 4 by reductive oxygenation and deprotection. 

Other than glycerol, the alditols (see Table II) all form strong complexes, so the technique is usually suitable for separations of free sugars from their reduction products.86 Removal of oxygen atoms from these derivatives, as expected, lessens their association with the acid. 

The racemization apparently takes place before hydrolysis. Similar results have been obtained with D-xylitol 5-phosphate and n-mannitol 6-phosphate. 1,4-Anhydro-ribitol is also formed from the treatment of ribitol with dilute mineral acid. However, since the anhydro compounds are produced more readily from the phosphates than from the unsubstituted alditols, it has been suggested that the latter compounds are not formed as intermediate products. The mechanism of this reaction has been explained by assuming protonation of the ester oxygen atom, with subsequent intra-... 

Alditols do not epimerize in oxygen-free, dilute alkaline solutions at temperatures used for alkaline-degradation reactions. 

Aldose reductase has been utilized for the selective reduction of aldos-2-uloses to 2-ketoses. Singlet oxygen oxidation of alditol-1-C-ylfurans 8 has afforded quantitative yields of enosuloses 9. Conjugate addition to enone 10 readily afforded the 2-deoxy-a-hexos-3-ulosides 11 and thioglycosidic analogues." l-C-(2-Thiazolyl)-... 

Aldoses and alditols can be rapidly oxidized by hydrogen peroxide under certain conditions leading to the formation of formic acid with evolution of oxygen, and a mechanism was proposed involving catalysis by superoxide radicals generated from traces of transition metal salts in Fenton s reaction ferrous ion is considered to play an analogous catalytic role. ... 

AnhydrO Alditols- An improved preparation of the four epoxybutanediol acetonides 24 (RR,RS,SR or SS) from L-ascorbic acid or D-isoascorbic acid (cf. Vol. 24, p. 195, ref. 16) has been described. The conversion of these isomers into enantiomerically pure glyceraldehyde derivatives, threose/erythrose derivatives or 2,3-anhydro threose/erythrose derivatives by initial treatment of 24 with various organometallic reagents is also reported. These latter compounds are useful building blocks for the synthesis of acyclic oxygenated fatty acid metabolites. 

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