Inositols configuration

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 power of the new spectrometer to reveal configurations of difficult cyclitols or sugars was first tested with mt/o-inositol (2), using deuterium oxide as solvent. At 60 or 100 MHz. the one equatorial and five axial protons appear to have different chemical shifts as shown by Lemieux in 1956 with a 40 MHz. instrument (14,15). However, since the five-proton axial signal could not be resolved, one could probably not have assigned the configuration 2 (which was already known from laborious chemical correlations extending over many years.)... 

D-myo-inositol is a six carbon polyalcohol in a ring structure arranged in a chair configuration. 

Base-catalyzed nitromethane cyclization of the dialdehyde generated by periodate oxidation of 1,2-O-cyclohexylidene-myo-inositol affords the nitrodiol with 1,4/2,3,5-configuration. This is converted into the a-mannosidase inhibitor, mannostatin A (Eq. 3.60).98... 

A single enzyme, inositol monophosphatase, leads to loss of the remaining phosphate and the regeneration of free inositol. This enzyme exhibits similar affinities for all five of the equatorial inositol monophosphate hydroxyls. Inositol 2-phosphate, which is not produced in this degra-dative pathway, is a poor substrate, a property that is probably attributable to its axial configuration. The enzyme is inhibited by Li+ in an uncompetitive manner i.e. the degree of inhibition is a function of substrate concentration. The putative link between the ability of Li+ to interfere with phosphoinositide turnover and its therapeutic efficacy in the treatment of bipolar disorders is discussed in Box 20-1 and Chapter 55. It should be noted that unlike most other tissues, brain can synthesize inositol de novo by the action of inositol monophosphate synthase, which cyclizes glucose 6-phosphate to form I(3)P. The enzyme has been localized immunohistochemically to the brain vasculature. 

A second problem that has repeatedly concerned us is the inability of the Sequence Rule to provide descriptors for some elements of stereoisomerism. When Cahn et al. (16) first encountered this problem with the all-cis and all-trans isomers of inositol, they attributed it to the fact that the symmetry has become so high that they have no asymmetric, nor even a pseudo-asymmetric atom. This interpretation, we believe, is incorrect. If the two ring ligands of any carbon atom of m-inositol were not heteromorphic, their exchange could not yield an isomer, as it clearly does. Each atom is a center of stereoisomerism with a pair of enantiomorphic ligands (Cg+g hi) and indistinguishable from the traditional pseudoasymmetric atom. The description of cu-inositol as all-5 could be accomplished by the same device that would allow one to specify the configurations of C(l) and C(4) of 4-methylcyclohexanol. 

Sugars and inositols are synthesized by the samarium(ll)-mediated cyclization methods. Stereoselectivity of newly introduced diol units is m-configuration in most cases. However, coordinating substituents sometimes affect the... 

ATP -I- 5-diphospho-lD-myo-inositol-pentakisphosphate = ADP -h bis(di-phospho)- D-myo-inositol tetrakisphosphate (isomeric configuration unknown)... 

There are two main points of interest. First, the extent of inversion varied over a wide range, and second, the high degree of inversion found for the aminodeoxy-scyiio- (46) and 3-amino-3-deoxy-chiro-inositol acetates was in marked contrast to the predominant retention of configuration observed in the deamination of simple, equatorial amines. 

Inositol is 1,2,3,4,5,6-hexahydroxycyclohexane. Draw configurational formulas for all possible stereoisomers and indicate which would be expected to be optically active. 

C NMR has proven to be one of the most efficient spectroscopic methods for configurational and conformational investigations in carbohydrate chemistry. The signal assignments of mono-, di- and polysaccharides, inositols and polyols are carried out on the following basis ... 

Figure 5. Chair configuration of myo-inositol hexaphosphate, illustrating hydrogen bonding between phosphate groups 2 and 6. Hydrogen bonding between groups 3 and 5 is not shown for clarity.

According to the Angyal proposals, the cyclohexanepenfo/s are all called quercitols, and these compounds, like the pentahydroxycyclohexanones inososes), are differentiated by trivial prefixes, the same prefix being used for the quercitol and the inosose of the same configuration. These prefixes are shown under the formulas CXXXIX-CXLIV (see p. 190). In the Fletcher-Anderson-Lardy system, these compounds are named as deoxy and keto derivatives, respectively, of inositols. The Angyal names will be... 

In these cases, solvolysis occurs with complete inversion, and only one inositol is formed. This seems to be the normal course of the reaction. In two instances, however, those of 1-O-tosyl- and 6-0-tosyl-epf-inositol, two inositols are formed, one by inversion and the other by retention of the configuration.62 An insufficient number of examples of solvolyses has yet been accumulated, to allow predictions about the stereochemical outcome of the reaction. 

The structures of the di-O-isopropylidene acetals of deatfro-inositol and Zero-inositol were determined by lead tetraacetate oxidation, and the results of these degradations confirmed the configurations previously assigned to the two active inositols.1 The dextro compound gave61 the di-O-isopropyl-idene acetal of D-monno-hexodialdose (LVII), which was reduced by sodium... 

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