Hudson’s rule

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. 

In the process of lactonization of L-tryptophan or its DNP-derivative a second asymmetric center is formed, probably stereoselectively, by induction from the existing center. Opening of this DNP-lactone and application of Hudson s rule (cf. Witkop, 1956 Vanderhaeghe and Parmentier, 1961) has so far pointed to the Dq structure for the spirooxindole-/3-carbon (Ramachandran, 1961), but this preliminary observation on a colored lactone derivative must await conformation from, e.g., a carbobenzyloxy lactone derivative. 

These rotations were deduced from the rotations of the isomeric n compounds. I The rotations of the anomers have been reversed from those in the original paper, in view of Hudson s rule. 

Additional proof for the S-D-linkage in lactose was obtained by degradation to 2-0-/3-D-galactopyranosyl-glyceritol, to which Hudson s rules were then applied. This selective oxidation was achieved by two successive treatments with lead tetraacetate and sodium borohydride (see Fig. 1). 

Table 2.1. It should be noted that in the D-series the optical rotation of the a-anomers is always a more positive value than that of the corresponding (S-anomer (Hudson s rule).

The molecular rotation of an a-n-glycoside is about 350° more strongly positive than that of the corresponding /3-n-glycoside (Hudson s Rule)... 

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. ... 

Chiroptical studies on 1-thio-D-glycofuranosides and 1-thio-D-glycopyranosides and a discussion of Hudson s rules [10]. Review on the chemistry and biochemistry of branched chain sugars including determination of the configuration at the branched position [11]. 

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. 

These rules were empirical and based on observations of limited samples of compounds. Subsequent to Hudson s rule, it was found that there were exceptions to the rule, and it was proposed that a better system of nomenclature would be based on the absolute configurations in which the hemiacetal hydroxyl that is on the same side (cis) as the hydroxyl group reacting with the aldehyde or ketone is a-, and the hemiacetal hydroxyl that is on the opposite side (trans) is P-. 

Fig. 15.2 Proposed routes from L-sorbose, D-sorbitol, or D-glucose to 2KLGA in Gluconobacter strains. Three major routes from different substrates to 2KLGA are shown (Id) L-sorbose as the substrate (lb) D-sorbitol (2) D-glucose. In addition, other routes from D-glucose to 2KLGA via 5-keto-D-gluconic acid (see text in Sect. 15.2) and L-idonic acid are shown. Enzyme reactions described in the text are shown in thick lines. Inserted panel shows substrate recognition by PQQ-GLDH (Bertland-Hudson s rule)...

The assignment of the rotational isomers to the two formulas which can be written for them has been a difficult stereochemical problem. At first, in all sugars of the D-series the more strongly dextrorotatory form was called the a-form. Later it was noticed that the ot-form in the projection formula invariably has the hydroxyl group on the same side as the hydroxyl group determining the D-series (i.e. to the right in the D-series to the left in the L-series). The reason for this is that each C atom contributes a definite amount to the optical rotation (Hudson s rule of superimposition). In the Haworth formulas, this means that, if the OH at C-1 is down, we have the a-form if the OH is up, the /S-form. 

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