Improved Karplus Equations for 3JC1,H4 in Aldopentofuranosides: Application to the Conformational Preferences of the Methyl Aldopentofuranosides

The effects of electronegativity and stereochemistry upon three bond 1H−1H coupling constants (3JH,H) are widely appreciated and have been taken into consideration in the development of Karplus equations for H−C−C−H fragments. These equations have found particular use in the conformational analysis of molecules containing aldopentofuranose residues. This paper demonstrates the effect of anomeric stereochemistry upon 3JC1,H4 in aldopentofuranosides and proposes Karplus equations that account for this effect. These new equations are shown to provide improved results for the determination of furanose ring conformation when compared to those obtained solely with 3JH,H data. The equations described here should be applicable to furanose derivatives containing any substituent at the anomeric center.