Polyalcohol, cyclic

Conduritols and inositols are cyclic polyalcohols with significant biological activity. The presence of four stereogenic centers in the stmcture of conduritols allows the existence of 10 stereoisomers. Enzymatic methods have been reported for the resolution of racemic mixtures or the desymmetrization of meso-conduritols. For example, Mucor miehei lipase (MML) showed enantiomeric discrimination between all-(R) and all-(S) stereoisomers ofconduritol E tetraacetate (Figure 6.52). Alcoholysis resulted in the removal of the four acetyl groups ofthe all-(R) enantiomer whereas the all-(S) enantiomer was recovered [141]. 

Phosphatidylcholine (lecithin) is the most abundant phospholipid in membranes. Phosphatidylethanolamine (cephalin) has an ethanolamine residue instead of choline, and phosphatidylserine has a serine residue. In phosphatidylinositol, phosphatidate is esterified with the sugarlike cyclic polyalcohol myo-inositol. A doubly phosphorylated derivative of this phospholipid, phosphatidylinositol 4,5-bisphosphate, is a special component of membranes, which, by enzymatic cleavage, can give rise to two second messengers, diacylglycerol (DAG) and inositol l,4,5trisphosphate (InsPsi see p.386). 

This extension of the Smith analysis, involving methylation of the polyalcohol, has been studied in detail by Bose, both on model systems and on the Ti fructan.84 When a ffuctan is used, this method may give l-hydroxy-3-methoxy-2-propanone and l,3-dimethoxy-2-propa-none, together with methylated glycerols. These compounds may react further under methanolysis conditions to yield 2,5-dimethoxy-2,5-bis(methoxymethyl)-l,4-dioxane and l,3-dimethoxy-2-propanone dimethyl acetal, respectively. Several of these compounds may be obtained from sucrose by a model reaction. In view of the wide variety of hydroxy compounds obtained in this study,84 their separation and identification as benzeneboronates was investigated, and certain of the latter derivatives were purified by gas-liquid chromatography. The characterization of 1,2- and 1,3-diols by the mass spectra of their cyclic benzeneboronates has also been described.634... 

Inositols (cyclohexanehexaols, cyclitols) are cyclic polyalcohols with general formula CeH Oe (as monosaccharides) but they are markedly stable to heat, acids and alkalis. They are also difficult to ferment. 

Madsen was able to synthesize conduritols (cyclic polyalcohols) via RCM metathesis of tartaric acid or sugar derivatives using (2a) or (4a), making available a number of the possible conduritol diastereomers in just a few steps from the chiral pool (Table 3). ... 

Cyclic polyalcohols (or cyclitols , according to the nomenclature of sugar alcohols) also exhibit a very low affinity. The most important representative of this class of compounds is inositol,... 

Aldehydes readily react with alcohols into hemiacetals and acetals. The first reaction involves simple addition, whereas water is liberated in the second reaction. The reactions are acid-catalyzed and reversible. Acid catalysis is, however, not a necessary condition for the reaction to proceed. Frequently, particularly in the case of aliphatic aldehydes, the reaction proceeds without a catalyst. If both alcohol and aldehyde are bifunctional reagents, it is possible that cyclic structures may form or that polymerization may occur. Whether or not one or the other of these reactions occur depends on the energy factors, steric accessibility of the reaction sites, and finally, as in all reversible reactions, on the position of the equilibrium according to the concentration of reagents and products in the solution. Starch, being a polyalcohol, also reacts with aldehydes. This subject was formerly reviewed by Roberts.1274... 

Yamaguchi A, Hiyoshi N, Sato O, Bando KK, Shirai M (2009) Enhancement of cyclic ether formation from polyalcohol compounds in high temperature liquid water by high pressure carbon dioxide. Green Chem 11 48-52... 

The crown ether-like macro-cycle obtained by the above process was subjected to several chemical modifications. By methylation we have obtained compounds possessing solubility both in water and in organic solvents and ability to form complexes. On the other hand, by tosylation and LiAlH4 reduction of the polyalcohol we managed to get a "macro cyclic ring" of completely apolar character. The present study deals with the structural investigation of the above compounds. The so-called J-ECHO "l c-n.m.r. spectra of the acetylated and methylated derivatives show total symmetry of the compounds. 

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