Inososes reactions

Quebrachitol was converted into iL-c/j/roinositol (105). Exhaustive O-isopropylidenation of 105 with 2,2-dimethoxypropane, selective removal of the 3,4-0-protective group, and preferential 3-0-benzylation gave compound 106. Oxidation of 106 with dimethyl sulfoxide-oxalyl chloride provided the inosose 107. Wittig reaction of 107 with methyl(triphenyl)phos-phonium bromide and butyllithium, and subsequent hydroboration and oxidation furnished compound 108. A series of reactions, namely, protection of the primary hydroxyl group, 0-debenzylation, formation of A-methyl dithiocarbonate, deoxygenation with tributyltin hydride, and removal of the protective groups, converted 108 into 7. 

Certain reactions previously considered to be ionic (49) may also take place by free-radical mechanisms, especially in nonaqueous solvents. Thus, the aromatization of mt/o-inosose-2 in acetic anhydride and pyridine to 1,2,3,5-tetraacetoxybenzene may take place by an ionic and a free-radical mechanism. Other free-radical mechanisms are discussed by Fatiadi in another chapter of this volume. 

Attempted Acetylation of D-Mannose Phenylhydrazone. Five grams of D-mannose phenylhydrazone was acetylated as described for myo-inosose-2-phenylhydrazone. Work-up of the reaction mixture (after 24 hours) gave a yellow syrup (3.6 grams) which failed to crystallize. TLC analysis of this syrup showed only a small proportion of an olefinic... 

Scheme 3.—Reactions of Radicals Derived from scyllo-Inositol. [The G-values of products77 in the y-radiolysis of a NjO-saturated, 0.01 M solution of scyllo-inositol at 0° and a dose rate of 2.9 W.kg-1 are G(scy//o-myo-inosose, 40) = 3.0, G(myo-inositol, 39) = 2.1, and G(deoxyinosose, 43) = 1.1].

The process differs from the fermentation of D-glucose by the same organism. The initial reaction is believed to be a dehydrogenation to an inosose,137 and the next step may be a dehydration.46... 

Reactions of the carbonyl group of inososes include the addition of diazoalkanes, dithioacetal formation, reduction, hydrogenolysis, and phenyl-hydrazone formation. The epoxide CXXX, which is formed from scyllo-inosose pentaacetate and diazomethane, is the starting material for a considerable series of seven-carbon derivatives.1 Some of the newer compounds of this group are discussed on pages 187 and 188. 

It is remarkable that the nitrodesoxy inositols, when subjected to the conditions of the Nef reaction in the hope of obtaining inososes, did not react and were recovered unchanged.63... 

When the hydrogen transferred as hydride to the cofactor is retransferred to the same carbon atom in the product, the movement is far more difficult to detect. The conversion of D-glucose 6-phosphate (58) into lL-mt/o-inositol 1-phosphate (61) occurs by cyclization of the carbon skeleton, with formation of a new bond between C-l and C-6. When each carbon atom in turn was specifically labeled with tritium, there was complete retention of tritium, even in the presence of added NADH, although there was an apparent, small isotope-effect with D-glucose-5-t 6-phosphate.19 The mechanism proposed for the cyclization19 was an initial oxidation at C-5 to give NADH and xylo-hexos-5-ulose 6-phosphate (59), followed by an aldol reaction causing cyclization to lL-myo-inosose-2 1-phosphate (60), which is then... 

Sprinson and Chargaff have reported that scyllo-meso-inosose in bicarbonate solution rapidly reduced six moles of periodic acid while in weakly acid solution the reaction was less complete. 

An interesting transition from the inositol to the quercitol series has recently been accomplished by Posternak. While hydrogenation of scyllo-meso-inosose with platinum oxide as a catalyst in neutral solution gave the expected mixture of meso-inositol and scyllitol, it was found that, when the reduction was carried out in dilute sulfuric acid solution, two moles of hydrogen rather than one were consumed and the product was a desoxyinositol, presumably the symmetrical form XLIX. That this reaction does not proceed through an inositol is shown by the stability of mcso-inositol under the conditions of the experiment. 

The basic permanganate oxidation of conjugated 1,3-dienes is different from those reported for the 1,4-dienes above. Therefore, in the oxidation of cyclopentadiene and 1,3-cyclohexadiene (13) a mixture of five products 14-18 is obtained (equation 4) . In this reaction 14 and 16 are derived from the normal cis hydroxy la tions whereas 17 and 18 were said to be formed from 15 by hydration in what the authors term an epoxidic pathway. Formation of epoxy-diols under similar permanganate oxidations has been found for occidentalol (19), levopimaric acid (20) and a 1-chloro- or 1-bromo-l,3-diene (21) as an intermediate step in the synthesis of (+)-D-c/tfrc-3-inosose and (+)-D-c/r/ro-3-inositol (equation 5). The explanation for the epoxide formation in the oxidation of 1,3-dienes (13, 19-21) is not clear but may be connected to the fact that other additions of permanganate to dienes are possible beyond those commonly observed... 

Machado, A. S., Dubreuil, D., Cleophax, J., Gero, S. D., Thomas, N. F. Expedient syntheses of inososes from carbohydrates conformational and stereoelectronic aspects of the Ferrier reaction. Carbohydr. Res. 1992, 233, C5-C8. 

Hydrogenolysis of nonactivated ketones is a side reaction only when hydrogenation is run in acid. In inososes lacking two axial hydroxyls next to the keto group, hydrogenolysis occurs in dilute H2SO4 ... 

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. 

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... 

This procedure furnishes a practical method for the synthesis of inososes on a small scale. The yield is about 50%, but complete reaction is difficult to effect. The ketones can be isolated through their phenylhydrazones or by column chromatography. 

The Weerman degradation was employed in one of the first preparations of dialdoses, namely of n-f/ireo-tetrodialdose, using the diamide of D-glucaric acid as starting material. An inosose has been degraded to a pentodialdose by way of its disulfone and the Nef reaction, transformation of a 6-deoxy-... 

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