Inositols oxidation, catalytic

These results may be summarized as follows (1) Only axial hydroxyl groups of inositols can be oxidized catalytically. The oxidation is also applicable to the various blocked derivatives of the inositols. (2) The reaction proceeds only to the stage of the monoketone, even when more than one axial hydroxyl group is present. (3) If there are several nonequi-... 

Catalytic oxidation was first apphed to the inositols by Heyns and Paulsen. It was found that jni/o-inositol (23), in nearly neutral solution at 60°, can be oxidized to a monoketone with platinum-on-carbon or with Adams catalyst. Oxidation stops at the monoketone stage, 5delding only insignificant proportions of ring-fission and further oxidation products. Only the axial hydroxyl group on C-2 is oxidized, affording scyUo-inosose... 

Various blocked derivatives of myo-inositol (23) can be catalytically oxidized when the axial hydroxyl group is unsubstituted. Oxidations with Acetobader svboxydans are extremely sensitive to such substituents and are therefore, generally, not feasible. Sequoyitol (5-0-methyl-mj/o-inositol)... 

If two axial hydroxyl groups in a molecule are sterically equivalent, they are oxidized at the same rate. Thus, the oxidation of epi-inositol (32) gives racemic ( )-epf-inosose (33, 34), which is also obtained by the oxidation of mi/o-inositol (23) with nitric acid. As expected, neo-inositol (35) yields pure neo-inosose (36) on catalytic oxidation. Hydrogenation of the... 

Both (iea axial hydroxyl groups which would be expected to be oxidized at the same rate, the same oxidation products being formed in each case. Thus, the catalytic oxidation of deairo-inositol (37) gives pure (+)-vibo-inosose (38), and that of lewo-inositol (42), pure (—)-w o-inosose (43). The oxidations are carried out at 85-90°, in the presence of a platinum-on-carbon catalyst, by passing air through the reaction mixture. The bacterial oxidation of each of these inositols leads to a diketone. 

Both of the axial hydroxyl groups are sterically equivalent in the monomethyl ethers of dea methoxyl group. Catalytic oxidation of each would,... 

The catalytic oxidation of inositols having three axial hydroxyl groups leads again to the formation of monoketones only. Again, the reaction is remarkably selective. Angyal oxidized muco-inositol (50) to the inosose... 

Several compounds of the dialdose type (see formula, p. 299) have been prepared. Catalytic reduction of tetra-O-acetylgalactaric acid gave 2,3,4,5-tetra-O-acetyl-gfoZocto-hexodialdose 163). Lead tetraacetate oxidation of tetra-O-acetyl-myo-inositol, tetra-0-acetyl-a//o-inositol, and di-O-isopropyl-idene-D-inositol, respectively, gave the corresponding tdo-hexodialdose,... 

Scheme 41.32 The first catalytic asymmetric phosphitylation/oxidation of an inositol derivative by Miller et at. (er = enantiomeric ratio).

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