Optical rotation alditols

The small optical rotations of the alditols arise from the low energy barrier for rotation about C—C bonds, permitting easy iaterconversion and the existence of mixtures of rotational isomers (rotamers) ia solution (12). 

Consideration of rotatory powers of l,l-bis(acylamido)-l-deoxy-alditols showed79 certain correlations between optical rotation (d line of sodium) and configuration that can be summarized as follows. (a) When the acyl group is aliphatic (for example, acetyl or propionyl), the alditol will be dextrorotatory in water if the configuration of C-2 is S. (The rule does not apply to peracetylated derivatives.) (b) When the two substituents on C-l are benzamido and the configuration at C-2 is S, a solution of the alditol in pyridine will be levorotatory. Peracetylation does not alter applicability of this rule, (c) The abso-... 

Preliminary examinations of dextran structures were conducted by optical rotation, infrared spectroscopy and periodate-oxidation reactions. More detailed results can be achieved by methylation analysis [19]. The hydroxyl groups are methylated with methyl iodide after activation with sodium methylsulfinyl carbanion (Fig. 2). The methyl dextran is hydrolysed to the corresponding different methylated monosaccharides, which are furthermore reduced and peracetylated. The resulting alditol acetates of methylated sugars are separated by gas chromatography and identified by their retention times. In particular, a combined capillary gas-liquid chromatography/mass... 

A sugar component isolated from the lipopolysaccharide from Rh. capsulata was shown by m.s. (as its alditol acetate) to be a 6-deoxy-3-O-methylhexose. From its chromatographic mobilities and optical rotation, it was shown to be identical with 3-O-methyl-L-rhamnose (l-acofriose)... 

Acyclic Alditols. - A simple method has been described for transforming Fischer projections into zig-zag forms. Dipole-dipole interactions of D-sorbitol in water and methanol solution have been studied, and evidence for solute-solvent interactions presented. The preparation of 1,4-di-O-benzyl-L-threitol from L-tartaric acid in 4 steps has been reported. A study of optical rotations of (S)-propane-l,2-diol, D-t/ reo-butane-2,3-diol as well as some alditols and some deoxyalditols in aqueous and non-aqueous solution has been reported D-glucitol, for example, is dextrorotaiy in DMSO or HMPT but levorotary in water or pyridine. The dependence of rotation on the solvent is considered in detail. The mass spectra of some per-O-benzoylalditols have been described. ... 

Aldotetrose B must be D-threose because the alditol derived from it (o-threitol) is optically active (the alditol from D-erythrose, the other possible D-aldotetrose, would be meso). Due to rotational symmetry, however, the alditol from B (D-threitol) would produce only two NMR signals. Compounds A-F are thus in the family of aldoses stemming from D-threose. Since reduction of aldopentose A produces an optically inactive alditol, A must be D-xylose. The two diastereomeric aldohexoses C and D produced from A by a Kiliani-Fischer synthesis must therefore be D-idose and D-gulose, respectively. E and F are the alditols derived from C and D, respectively. Alditol E would produce only three C NMR signals due to rotational symmetry while F would produce six signals. 

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