Conformations of selected 3-substituted 4-hydroxycoumarins in solution by nuclear magnetic resonance. Warfarin and phenprocoumon.
The chemical shift position of the benzylic proton, Hx, has been found to be diagnostic in indicating the preferred conformations of selected 3-substituted 4-hydroxycoumarins. In general, the nonrigid open-chain compounds, e.g., to open-chain tautomer of warfarin and phenprocoumon, are found to exist in equal populations of the two conformations in which the benzylic proton is in the plane of the coumarin ring and is either cis or trans to the 3,4 double bond. The cyclic compounds, e.g., cyclocumoral, are constrained to two limiting conformations defined as axial2 or trans or intermediate conformations between these limits. Evidence is presented that suggests that the antivitamin K activity of warfarin is due to its open side-chain tautomeric form.
D015110:4-Hydroxycoumarins; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D010644:Phenprocoumon; D012996:Solutions; D014859:Warfarin
D015110:4-Hydroxycoumarins; D012996:Solutions; D014859:Warfarin; D010644:Phenprocoumon