Cyclitols configuration

Other carba disaccharides to have been prepared include carba-a-o-Glcp-, carba-a-D-Manp-, carba-P-D-Man/j- and carba-P-o-GIcNAcp- (l- 4)-l,6-anhydro-2,3-0-isopropylidene-P-D-mannopyranoses. The a-linked compounds were prepared by adding the anion of l,6-anhydro-2,3-C>-isopropylidene-p-D-mannopyranose to epoxide 98 and the P-linked derivatives were obtained from the a-linked compounds by epimerization after oxidation of the free cyclitol OH group. Further standard transformations of the free cyclitol OH also gave the cyclitol configurations noted above.In a similar way, opening of a cyclitol... 

According to the modified Maquenne system (18,19,31) used in this chapter, the diastereomeric configuration of any cyclitol is expressed by a fraction, and position-numbering, if otherwise equivocal, is so assigned that the numerator will have the lowest possible numbers. For example, proto-quercitol (12 or 13) is designated (134/25,), not (14/ 235) or (25/134). 

Until some uniform configurational nomenclature for cyclitols has been generally accepted, it would appear safer for authors in this field to specify the nomenclature used in every article, or to indicate configurations by means of formulas. 

The Synthesis of (— -proto-Quercitol, Although proto-quercitol (dextro) was discovered in 1849 ( 5), its cyclohexanepentol structure was not established until 1885 (13), and its configuration not until 1932. (38). The synthesis of this well-known cyclitol has been a difficult problem, since it appears that nearly every synthetic reaction commonly employed for other cyclitols would lead stereospecifically to the wrong product. 

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.)... 

With the new very high resolution NMR spectra, it should be a simple matter to assign configurations to other difficult cyclitols or carbohydrates, for example, the numerous still undiscovered isomers of 6-bromo, 6-chloro, and 6-iodoquercitol (20 diastereomers predicted for each). 

Cyclic monosaccharides, having nitrogen or sulfur in the ring, 23, 115-232 Cyclitols, 14, 135-212 chemistry and configurations of, 3, 45-77... 

M. Funabashi and J. Yoshimura, Branched chain sugars. Part 14. Synthesis of new branched-chain cyclitols having myo- or scyllo-, and muco-configuration from 3-< -benzyl-5,6-dideoxy-5-C-(l,3-dithian 2-yl)-6-nitro-L-idofuranose and D-glucofuranose, J. Chem. Soc. Perkin Trans, p. 1425 (1979). 

Since the new IUPAC recommendations [5], the nomenclature of quinic acid isomers is very confusing in the literature. Therefore, the latest IUPAC nomenclature is used throughout this paper instead of the older, but still useful, nomenclature. In the IUPAC nomenclature quinic acid is now treated as cyclitol. In the preferred configuration, the carboxy group and the C-4 and C-5 hydroxy groups are equatorial, with the C-l and C-3 hydroxy groups are axial. In the IUPAC system, the former 3-O-acylquinic acids are now renamed 5-O-compounds, and the... 

Electrophoresis on borate-buffered paper is potentially useful for the detection of cyclitols. So far, however, the principal application of this technique in the cyclitol field has been to studies on configuration and on the nature of cyclitol-borate complexes (see p. 153). 

The most important cyclitols are the inositols (1,2,3,4,5,6-cyclohexanehexols). The relative arrangement of the six hydroxyl groups below or above the plane of the cyclohexane ring is denoted by an italicised configurational prefix in the eight inositol stereoparents (the numerical locants indicate OH groups that are on the same side of the ring) ... 

The hexahydroxycyclohexanes have long been of particular interest to those concerned with the carbohydrates. Originally this interest arose from the fact that they are isomeric with the hexoses and resemble the sugars in water solubility and sweetness it has been sustained by their unique properties, their stereochemical relationships and, finally, by the tantalizing question of their significance in nature. The present review will deal chiefly with the chemistry and configurations of the hexahydroxycyclohexanes or inositols, as they are frequently called, and will touch on certain other closely related polyhydroxycarbocyclic substances. The convenient term cyclitol has come to denote the type of compound that will be considered herein. 

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