Conformation hydroxymethyl groups

C. Mayato, R. Dorta, and J. Vazquez, Experimental evidence on die hydroxymethyl group conformation in alkyl p-D-mannopyranosides, Tetrahedron Asymmetry, 15 (2004) 2385-2397. 

R. Stenutz, I. Carmichael, G. Widmalm, and A. S. Serianni, Hydroxymethyl group conformation in saccharides Structural dependencies of 2JHH, 3JHH, and 1JCH spin-spin coupling constants, J. Org. 

R. Stenutz, Hydroxymethyl groups, conformation of hydroxymethyl groups determined from... 

R. Stenutz, Hydroxymethyl groups, conformation of hydroxymethyl groups from 3/h-5,h-6> http // www.stenutz.eu/conf/hm div.html. 

S. A. H. Spieser, J. A. van Kuik, L. M. J. Kroon-Batenburg and J. Kroon. Improved carbohydrate force field for GROMOS Ring and hydroxymethyl group conformations and exo-anomeric effect. Carbohydr. Res. 322, 1999, 264. 

According to a recent report, the unit cell of cellotetraose hemihydrate in single crystals contains two antiparallel chains, which are conformationally distinct—especially in the sugar geometries.74 However, all hydroxymethyl groups adopt similar gt orientations. Whether this oligosaccharide morphology can be implemented for cellulose II in fibers remains to be seen. 

The 18 hydroxymethyl groups in one turn of the triple helix have quite different orientations. b The two residues per turn are conformationally independent. 

An additional example of a cycloamylose-induced rate acceleration which may be reasonably attributed to a conformational effect is the facilitation of the transfer of the trimethylacetyl group from the phenolic oxygen of 9 to the aliphatic oxygen of the adjacent hydroxymethyl group to form 10. This intramolecular transesterification is remarkably enhanced relative to a comparable intermolecular reaction,6 and occurs, at pH 7.0 and 25.5°, with a rate constant of 0.0352 sec-1 (Griffiths and Bender, 1972). An even larger rate enhancement is achieved upon inclusion of this material within the cyclohexaamylose cavity—fc2 = 0.16 sec-1. This fivefold acceleration cannot be satisfactorily explained either by a microsolvent effect which would be expected to depress the rate of the reaction or, at this pH, by covalent... 

Figure 2 depicts the relevant cyclopentane conformations for either di-astereomeric alcohol 48. Conformations A and C would lead to the desired cis-anti-cis tricyclodecane skeleton of kelsoene whereas conformations B and D would be responsible for the formation of the undesired cis-syn-cis product. We were convinced that the influence of the stereogenic center to which the hydroxymethyl group is attached (" ) was marginal as compared to... 

Fig. 18. Thymidine (dT) and an oxepanyl analogue (oT). Structures on the bottom (taken from ref. 149) show minimized conformers for both dT and oT, emphasizing the similarity in the disposition of the base and the C-4/C-6 hydroxymethyl group.

C. Nobrega and J. T. Vazquez, Conformational study of the hydroxymethyl group in a-D-mannose derivatives, Tetrahedron Asymmetry, 14 (2003) 2793-2801. 

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