Dynamic stereochemistry of rutin (vitamin P) in solution: theoretical approaches and experimental validation

Rutin, vitamin P, was extracted from Salvia macrosiphon and identified by ¹H, ¹³C, ¹H–¹H COSY, HMQC, and HMBC spectroscopy. In parallel, density functional theory (DFT) using B₃LYP functional and split-valance 6-311G∗∗ basis set has been used to optimize the structures and conformers of rutin. Also experimental and theoretical methods have been used to correlate the dependencies of ¹J, ²J, and ³Jinvolving ¹H and ¹³C on the C5″–C6″ (ω), C6″–O6″ (θ), and C1‴–O6″ (φ) torsion angles in the glycosidic moiety. New Karplus equations are proposed to assist in the structural interpretation of these couplings. ³J_HH depends mainly on the C–C (ω) torsion angle, as expected, and ²J_HH values depend on both C–C (ω) and C–O (θ) torsions. ¹J_CH values within hydroxymethyl fragments were also examined and found to depend on r_CH, which is modulated by specific bond orientation and stereoelectronic factors. In all calculations solvent effects were considered using a polarized continuum model (PCM).