Isorotation rules

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

The description in the literature of numerous pairs of < - and /3-isomers of amino sugar derivatives facilitates a rather more detailed consideration of the application of the isorotation rules than has hitherto been the case. -88 The appropriate derivatives are listed in Tables III and IV together with the necessary rotational data and calculations. 

Hudson isorotation rules, III, 17 Hyaluronic acid, II, 164, 179 sulfate, II, 164, 184... 

Baker trans rule or the Hudson isorotation rules have to be taken with care in view of some anomalies.11,38,39 Nuclear magnetic resonance spectra 38 and optical rotatory dispersion curves 38,40,41 have been recently applied to determine the configuration of pyrimidine nucleosides at the anomeric center. 

The negative optical rotation of 5-acetamido-5-deoxy-a-D-xylopyra-nose is in contradiction to its existence as the a-D anomer. As Fig. 2 shows, the methyl D-xylopyranoside that corresponds to the a-D form, according to the Hudson isorotation rule, shows a positive plain curve and the p-D form shows a negative plain curve in optical rotatory dispersion. On the other hand, 5-acylamido-5-deoxy-a-D-xylop)franoses and their glycosides exhibit negative plain curves. Obviously, the... 

Benzyloxycarbonyl)amino]-5-deoxy-D-ribopyranose (208) was separable into its two anomers. In accordance with the above concept, the a-D anomer shows an upward mutarotation and a negative plain curve, whereas the )8-d anomer exhibits a downward mutarotation and a positive plain curve. A further deviation from the Hudson isorotation rule is observable with 4-acetamido-l-0-acetyl-4-deoxy-2,3,5-tri-0-p-nitrobenzoyl-/8-D-ribofuranose. ... 

If the amide chromophore is removed from methyl 5-[(benzyloxy-carbonyl)amino]-5-deoxy-a-D-xylopyranoside (40), or from its non-glycosidic form (31),a positive plain curve of optical rotatory dispersion is found for 5-amino-5-deoxy-D-xylopyranose (17) and its methyl glycoside (41). Because, at least with the glycoside 41, no reversal of configuration at C-1 is to be expected under these conditions, 5-amino-5-deoxy-D-xylopyranose and its methyl glycoside likewise show a tendency to assume the o-D anomeric form, and show plain curves in agreement with the Hudson isorotation rule. ... 

Hudson observed similarities in the rotatory power of some configurationally related examples he was, however, unable to generate workable isorotation rules for the dithioacetals276,417 later advances in conformational analysis32,33 1 0 2,344 have revealed that the conformational uniformity implicit in the isorotation treatment is not... 

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. 

This study is of interest because Davoll and Lythgoe observed that the more deaiirorotatory anomer of the acylated theophylline nucleosides yielded the more Uvo-rotatory anomer of the free nucleoside. Because of this anomaly, these investigators suggested that the isorotation rules of Hudson have only hmited validity in the case of nucleosides of 2-deoxy-D-ribose and were unable to assign a definite configuration to the anomers. 

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. 

The unsaturated phosphonates typified in (2) do not conform with Hudson s isorotation rule the conformational free energy for the dimethylphosphono group was found to be 8.34 kJ mol and its anomeric effect was calculated to be 2,33 kJ mol . ... 

OPTICAL SUPERPOSITION, THE ISOROTATION RULES, AND THE INFLUENCE OF STRUCTURE ON OPTICAL... 

The hypothesis of the additive nature of the rotatory contributions of the individual asymmetric centers of steroisomers in making up the total rotation of each isomer was formulated by van t Hoff and has been known as the principle of optical superposition. In its full generalization as applied to all substances, the hypothesis of optical superposition is definitely unsound and thus it is not a principle nevertheless, it has been shown by Hudson (116) that the hypothesis holds in first approximation for a large number of carbohydrates, and the approximation is sufficiently close to permit valuable inferences concerning structure and configuration to be drawn from comparisons of the rotations of carbohydrates through the application of his Isorotation Rules. 

In a similar fashion, application of the Isorotation Rules led to the inference 119) that the biose constituent of the glycoside amygdalin is gentio-... 

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