Correlation furanosides

On the grounds that furanosides anomerise and hydrolyse very much more readily than do the corresponding pyranosides. Bishop eind Cooper assumed that the first step in the glycosidation process is the methanol-ysis of the furanose form of the free sugar, and they visualised, without evidence, a unimolecular process proceeding by way of a stabilised cyclic ion (1). In support of this they observed 5) that for xylose, lyxose and ribose the furanoside formation rates (3,1,12 respectively) correlated with the furanoside contents at equilibrium (see Table 3) and hence, presum-... 

The high rate-constants found for the D-glucofuranosides and D-xylo-furanosides were unexpected. No correlation is observable of the relative stability of the various aldofuranosides with the order shown in acidic... 

Finally, the anomeric resonance at 5.068 ppm showed a direct correlation to the C resonance at 108.66 ppm in the HMQC spectrum, indicating that galactose residue D is the /3-furanoside form (Beier et al. 1980). 

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. ... 

Additional studies are underway to assess the ability of the RdPCA model to represent conformational space among different species. The perspectives opened by this preliminary research are to incorporate exocyclic dihedral angles into the RdPCA analysis, in order to probe the effects of exocyclic substituents on ring dynamics and eventually to analyse correlated motions within oligosaccharide structures, as well as to generalize this RdPCA analysis to other cyclic structures, such as not only furanosides, but also pyranose rings and even cyclodextrins. 

The resonances of the benzyl methylene carbon atoms of eight per-Q-benzylated methyl furanosides have been assigned by means of INADEQUATE and - C- H correlation n.m.r. methods. The chemical shifts of these carbons and the values between the ring... 

A thorough analysis of the C n.m.r. spectra of methyl aldopento- and aldo-hexo-furanosides and several cyclopentanols has enabled the C chemical shifts to be correlated with the configurations and other stereochemical features of vicinal diol groupings. Values for both /uc-i,f and /i c-2.p furanosyl... 

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