Meso-Inositol configuration

The difficult proof of the configuration of meso-inositol has come only recently from two independent sources, each proof representing the culmination of a long series of researches. The work of T. Posternak, although second in actual priority, will be described first. 

Of the nine possible configurations, VIII and IX were eliminated at the outset since they contain no plane of symmetry and represent optically active compounds while meso-inositol is inactive and unresolvable. The action of phosphatase on meso-inositol hexaphosphoric acid ester ... 

Recourse was then had to the direct oxidation of meso-inositol with alkaline potassium permanganate, and a hexaric acid was obtained which proved to be identical with allomucic acid prepared previously by Emil Fischer. Since the configuration assigned to this acid placed the four hydroxyl groups in a cis-cis-cis relationship, all the remaining configurations for meso-inositol save II are seen to be inapplicable. From the mother liquors of the oxidation mixture D,L-glucosaccharic acid was also isolated. This result, however, only showed that form IV was untenable. 

In 1941 Posternak studied scyllo-meso-inosose (see p. 65), a penta-hydroxycyclohexanone which had been obtained by Kluyver and Bo-ezaardt from the biochemical oxidation of meso-inositol. Cautious oxidation of scyllo-meso-inoaose with permanganate led Posternak to the isolation of a hexaric acid which he identified as n,L-glucosaccharic acid. Since, of the two forms II and V, only II can give an optically inactive inosose oxidizable to D,L-glucosaccharic acid, this evidence appeared to settle the configuration of meso-inositol. 

The question of the configuration of epi-meso-inosose has recently been answered by Posternak. Examination of the formula for meso-inositol (V) will reveal that oxidation might give rise to six inososes. Attack at the equivalent positions one and three would give the enantio-morphous pair of inososes (XXXIII and XXXIV). In precisely the same manner, oxidation of carbons four and six would give the enantio-morphous pair XXXV and XXXVI. On the other hand, oxidation at either position two or five would result in the formation of the sym-... 

The most important compound is wyo-inositol, (1Z,2Z,3Z,5Z, 4 ,6 )-cyclohexane-l,2,3,4,5,6-hexol, formerly also called meso-inositol (or i-inositol, phaseomannitol, nucitol, bios I, mouse antialopaecia factor or vitamin Bjjj). The affix myo was preferred to the affix meso as it defines a certain configuration of hydroxyl groups above and below the plane of the ring (1,2,3,574,6-), while the second affix has a general meaning and is used to label achiral, optically inactive compounds with the same number of identically bound enantiomeric groups. 

The latter on ammonolysis gave the free pentol, m.p- OS . The meso(1245/3) configuration was established by correlation with 2,3-an-hydro-epf-inositol (115), correlated in turn with conduritol-F (113), and DL(1235/46)-inosamine. 

The tetrol configurations meso(1234) and weso(14/23), (62 and 60), were established by chemical correlations with mcso-epi-inositol (18) and meso-conduritol-A (32), both of previously known configuration. The absolute configurations of the eight active orfAo-tetrols were established by indirect chemical correlations with (—)-t 6o-quercitol (30), (-l-)-pinitol (66), (—)-inositol (93), and (— )-quebrachitol (93, 2-methyl ether), all of known, absolute configuration. 

In 1954 McCasland and HorswilP obtained a me/a-tetrol, m,p. 180 , by hydrogenolysis of a dibromotetrol (74), m.p. 216°, derived from myo-inositol (73). From the assumed mechanism of formation of the dibromotetrol, it was proposed that the configuration of the tetrol is meso(13/25) (75) and this has been confirmed by nuclear magnetic resonance (see p. 53). ... 

In its meso-configuration, inositol can be phosphorylated. Corresponding procedures for the separation and determination of various inositol phosphates were introduced by Smith and MacQuarrie [162]. 

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