Hudson’s rules, of isorotation

The uniqueness of the aldofuranosides, as compared to the aldopyrano-sides, was recognized initially through the difference in rates of hydrolysis by acid. This difference was confirmed by the use of methylation techniques the latter have, to a great extent, been supplanted by the periodate oxidation of Jackson and Hudson120 and by oxidation with lead tetraacetate. Hudson s rules of isorotation were also employed to a great extent. 

Exceptions to Hudson s Rules of Isorotation. The Nuclear Magnetic Resonance Spectra of Anomeric Pyrimidine 2-Deoxy-D-ribonucleo-sides, R. U. Lemieux and M. Holfer, Can. J. Chem., 39 (1961) 110-115. 

Later a number of other oligosaccharides of trehalose type were prepared.49 A trehalose, assigned the a, -configuration on the basis of Hudson s rules of isorotation,47 was prepared in 15% yield by treating a toluene solution of D-glucose tetraacetate first with zinc chloride and then with phosphorus pentoxide. 

Hudson s rules of isorotation are used for the determination of the configuration at the anomeric centers in oligo- and poly-saccharides and Korytnyk has discussed some extensions of these rules. Reeves has demonstrated that studies of the optical rotation in cuprammonia solution can give valuable information on the types of linkages and also on the conformation of sugar residues in a polysaccharide. Bourne and coworkers have shown that some o- and /S-D-glycosidic linkages display characteristic absorptions in the infrared at 844 and 891 cm, respectively. 

Hudson s Rules of isorotation have been applied to furanosides and a correlation with known conformations of methyl aldofuranosides made. The molecular rotations and differences in molecular rotation were tabulated for all aldo-pentoses, aldohexoses, and hexuloses as their methyl furanosides, and hence their conformations were deduced. The jS-D-pentofuranosides were mainly in the T2 form with the 0-methyl group quasi-axial and the side-chain quasi-equatorial, whereas the a-D-pentofuranosides were either in the E form or a mixture of T forms. The optical rotations for all a-D-furanosides are negative, but for 3-d-furanosides they are all positive. ... 

Details of the synthesis and reactions of glycofuranosylethynes, prepared via the reaction of 2,3 5,6-di-0-isopropylidene-a-D-mannofuranose with ethynyl magnesium bromide, have been published (see Vol. 8, p. 27). It is noteworthy that the glycofuranosylethynes do not obey Hudson s rules of isorotation. 

B = 2A and Ma + Mp = A+ B A+B = 2B, Hence, the partial rotations may be obtained by adding the molecular rotations of anomers to give 2B and by subtracting the molecular rotation of the /S-isomer from that of the a-isomer to give 2A. The partial rotations are one-half of each of these sums and differences. As a result of the measurement of the rotation of many a-/ pairs in the sugar series, Hudson was able to formulate the two Rules of Isorotation ... 

Application of Hudson s Isorotation Rules to 2-Amino Sugar Derivatives... 

The first of these was van t Hoff s principle of optical superposition, namely, that, in a compound having two or more asymmetric carbon atoms, the optical activities of the individual atoms can be added algebraically. This principle was applied with considerable success to carbohydrates by Hudson, in the form of his well known isorotation, lactone, and amide rules. These rules have been reviewed elsewhere, " and will not be discussed here. 

Hudson isorotation rules. For anomeric (a and (3) sugars, Hudson s isorotation rule states that (1) the rotation of carbon 1 in many sugar derivatives is affected in only a minor degree by changes in the structure of the rest of the molecule and (2)... 

Since both acids may be degraded to Al-acetylneuraminic acid, they evidently differ as regards the position of the 0-acetyl group. The possibility that they are anomers is indicated on comparing their molecular rotations with that of Al-acetylneuraminic acid ([M] — 9,888) and applying Hudson s isorotation rules. 

Ultraviolet, infrared, and x-ray data on compound 45 have been reported,81 and it has been pointed out4 that, in this series, the anomeric pairs of glycosides that have so far been examined conform with Hudson s isorotation rules, unlike some 2,3-unsaturated glycosyl esters.51,91 Features of the nuclear magnetic resonance spectra are... 

After methylation of compounds (50, R = Me) and (51, R=Me) with methyl sulfate, four isomeric pyranosides were isolated by gas-liquid chromatography by detailed nuclear magnetic resonance studies, these were shown to exist in the H° conformation.103 Unlike related esters (see p. 221), but like other 2,3-unsaturated glycosides (see p. 237), these anomeric pairs of glycosides were found to conform with Hudson s isorotation rules. In dilute acid, they are degraded to methyl 3,4-dideoxy-6-0-methyl-a- and /3-D-g/ycero-hex-3-enopyrano-sidulose (52) these also were characterized configurationally and conformationally by nuclear magnetic resonance methods. 

Hudson s isorotation rule was subsequently expanded by Whiffen, who suggested a set of empirical rules based on additive contributions to the molecular rotation based on contributions along each asymmetrically substituted bond. He established six structural parameters and assigned to each of these a numerical value, making possible an estimation of the molecular rotation in aqueous solution of the various pyranoses.195... 

A notable feature of the unsaturated acetates (66) is that the a-D anomer is less dextrorotatory than the /8-d anomer over the wavelength range of 250-600 m t, so that this is an exception to Hudson s Isorotation Rules. After hydrogenation, the products are no longer anomalous, and it is presumed that the unsaturated chromophore adjacent to the anomeric center is responsible for this property. 

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