Inososes reduction

In addition to the methyl ethers of dextro-, levo-, and myo-inositol which have been discussed in the preceding paragraphs, methyl ethers of most of the other inositols are now known. These compounds have been incidentally obtained in the course of other investigations—by the reduction of inososes formed from known ethers, by the inversion of tosyl esters of known ethers, and by opening the epoxide rings of anhydroinositols with methoxide ion. The individual compounds are listed in Tables II-X, pp. 192-203. 

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. 

The reduction of inososes is a method much used for the preparation of new cyclitols. Catalytic hydrogenation in neutral, aqueous solution yields predominantly the isomer with the newly formed hydroxyl group in the axial position,210 whereas the product from a reduction by sodium amalgam usually contains considerable quantities of both the possible epimers.211 Recently, sodium borohydride has been used for reducing inososes62,68 211 in some cases, but not in others, it provides more of the equatorial isomer than does sodium amalgam. 

Three inosamines were obtained in the course of efforts to synthesize myo-inositol by the nitro-sugar cyclization (see p. 142). However, the methods which have been the most productive of new inosamines are those which are well known as means of preparing amino sugars and aminopolyhydric alcohols, namely, reduction of imine derivatives of carbonyl compounds (in this case, inososes) and ammonolysis of halohydrins and epoxides. 

Cautious nitric acid oxidation of meso-inositol afforded Postemak a pentahydroxycyclohexanone. Reduction of this compound or its pentaacetate gave a new inositol which Postemak named epi-inositol. Proof of the structure of the pentahydroxycyclohexanone epi-meao-inosose, see the following section) as a racemic mixture of 1-keto- and 3-keto-meso-inositol (XXXIII and XXXIV) demonstrated that ept-inositol corresponds to formula II. 

D,L-talomucic and D,L-glucosaccharic acids. epi-meso-Inosose is therefore the racemate represented by XXXIII and XXXIV while the reduction product epi-inositol is II, representing as it does, an inversion of... 

Both Chargaff and Magasanik as well as Posternak have shown that cpi-inositol is oxidized by Acetobacter suboxydans to a levorotatory inosose. Postemak found that reduction of this compound with sodium amalgam in acid solution gives a mixture of meso-inositol and cpf-inositol, proving that the substance is one of the enantiomorphs XXXIII or XXXIV. Since oxidation with permanganate afforded D-talomucic and D-glucosaccharic acids, the levorotatory cpf-meso-inosose must be represented by XXXIII. 

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 reduction of keto-cyclohexane compounds, including some inososes,i has been widely studied and it has been found that hindered keto groups afford axial hydroxyl groups, and that the proportion of axial to equatorial hydroxyl groups formed is dependent on the type of reduction. It was found that the results with the keto-pyran compounds (the keto-D-gluco-pyranosides) were rather similar to those obtained with the related keto-cyclohexane compounds (the inososes). 

Posternak has shown that the keto group in m2/o-inosose-2 can be reduced to a methylene group by catalytic reduction over Adams catalyst in acid solution. Lindberg and Theander applied these conditions to... 

Cyclization of known 2,6-di-0-benzyl-L-ara6mo-aldohexos-5-ulose with DBU afforded the inosose 161 in 60% yield by intramolecular aldol condensation. Hydrogenolytic removal of the 0-benzyl groups followed by stereoselective reduction with sodium borohydride produced epi-inositol in high yield. ... 

In the interest of devising simple routes to starting materials commonly used in synthesis from sustainable resources, catechol has been made chemo-enzymatically in two steps from glucose in reasonable yield. 2-Deoxy-scyllo-inosose (171) was formed by incubation of D-glucose with recombinant 2-deoxy-scyl/o-inosose synthase and a hexokinase, and this material was reductively dehydrated to catechol by treatment with HI in acetic acid. ... 

A potential two-step process to convert D-glucose to catechol (48) via D-glucose-6-phosphate (46) has been developed. This comprises a one-pot incubation of the sugar with hexokinase and recombinant 2-deoxy-scy//o-inosose synthase, followed by chemical reductive dehydration of the resulting 2-deoxy-scy/to-inosose 47 with hydrogen iodide (Scheme 10). ... 

Substituted (eg aminobenzoyl) myoinositol 1,3,4,5-tetralds- and 1,3,4,5,6-poitakis-phosphate and the tritiated derivative 128 have been prepared, the latter by reduction of the corresponding benzyl protected inosose with potassium borotritiide followed 1 l drogoiolysis. 

D-glucose. This transformation has recently been demonstrated (32b), Synthesis in vitro is based on the work of Grosheintz and Fischer (S3). They found that 6-deoxy-6-nitro-D-glucose (or, likewise, 6-deoxy-6-nitro-L-idose) condensed in slightly alkaline solution to form two monodeoxymononitro-iiiositols. These were converted to the corresponding amines, one of which can also be obtained by reduction of the phenylhydrazone or oxime of mi/o-inosose-2 (scyllo-myo-inosose) h). The final and crucial step,... 

An optically inactive isomer, 2-deoxy-myo-inositol (deoxy-scyZZo-inositol) (scylloqneTcitol (7)), m.p. 233-235 , was synthesized by the catalytic reduction of m2/o-inosose-2 in the presence of mineral acid (56) (Fig. 1). Catalytic reduction of inososes or their oximes in mineral acid appears to be a general way for preparing monodeoxyinositols (57a, 6). 

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