Inositol, alio scyllo

Of the nine stereoisomers of inositol, the scyllo-isomer has no axial hydroxyl, the myo-isomer has one, the epi-, chiro-, and neo-isomers have two, and the alio-, cis-, and mneo-isomers have three hydroxyl groups (Figure 1). Of these, six isomers scyllo-, myo-, epi-, neo-, cis-, and mr/co-i somers) have one or more planes of symmetry in the molecule (meso compounds) and are therefore not chiral. D-chiro- and L-e/u>o-i somers do not have a plane of symmetry and are chiral molecules moreover they are enantiomers of each other. The alio-isomer is unique - the conformational isomer of (10) (Figure 2) is (11) which is also its enantiomer Since interconversion between conformational isomers is rapid, a//o-inositol exists as a 50/50 mixture of the two enantiomers at room temperature. Therefore, although alio-inositol is chiral, the compound is optically inactive at room temperature because it is a racemic mixture a chiral reagent, such as an enzyme, would be expected to preferentially react with one enantiomer and not the other. 

Lee and Ballou111 investigated five liquid phases for the separation of inositol trimethylsilyl ethers and concluded that QF-1 gave the best results. This column packing permitted resolution of all but the myo-cis pair of inositols. They reported that the order of appearance, regardless of the stationary phase used, is alio, (neo, muco), racemic, (scyllo, epi), and (myo, cis). The order within the parentheses is sometimes reversed, depending on the liquid phase used. Wells and co-... 

Well known alternatives to this fractional notation are based on the use of a set of eight prefixes alio, cis, dl, epi, muco, myo, neo, and scyllo) for the inositol configurations, and of ten prefixes alio, cis, epi, gala, muco, neo, proto, scyllo, talo, and vibo) for the quercitol configurations. Since these nomenclatures, due mainly to Fletcher, Anderson and Lardy, and... 

The mass spectra of isomeric inositols do not show a molecular ion peak but the latter can be deduced from the presence of an M - - 1 peak at m/e 181 (21). Facile elimination of water gives rise to m/e 163. Judging from the relative intensity of this peak, the ease of elimination of water appears to be in the order neo > scyllo > alio > muco > levo > myo > epi > cis. 

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