Pyranose and Related Systems

A united atom molecular mechanics parameter set for pyranoses has been developed from ab initio molecular orbital calculations and used to compute anomeric free energies for a series of simple monosaccharides in water. An empirical method has been employed to predict the magnitudes and signs of two-bond spin coupling constants in aldopyranosyl rings. Although designed 

Vcoc values and conformational analysis of O-glycosidic linkages has not been excluded.  

Special attention was given to the conformations about the C-5-C-6 bond in semiempirical quantum mechanical nuclear shielding calculations on a series of hexopyranoses, and in molecular mechanics simulations of methyl a- and P-d-gluco-, -galacto-, and talo-pyranoside in aqueous solution, as well as to the conformation of the acetamido group in 2-acetamido-2-deoxy-D-allo- and -d-gluco-pyranose derivatives, such as 18-20.  

Examination of spin-lattice relaxation times and second moment measurements of crystalline monosaccharides revealed jump motions of a hydrogen-bonded hydroxyl proton in P-D-allopyranose and transigauche reorientations of the CH2OH group in D-allopyranose and methyl a-D-mannopyranoside. Structural and conformational studies on the mannose-derived amidine 21 and related 

NMR spectroscopy played a vital role in the identification of disaccharides 25 and 26, the former obtained in the chitosanase digestion of the chitinous component of a fungal cell wall, ° the latter isolated as an aroma precursor of tea leaves. In connection with the complete and C-NMR assignment of a 

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