2D-NOESY in conjunction with aromatic solvent induced shifts (ASIS) allowed unequivocal assignments of methoxyl resonances in polymethoxylated pyranoflavones thus
providing an additional aid for the structural elucidation of natural products. In addition, the unusual nOe interactions observed in 2′-substituted B-ring flavones with H-3 or H-4 ″of
the pyran ring suggested hindered rotation of the B-ring.
A. Banerji and Luthria, D. L., “Assignment of Methoxyl Resonances and Observation of Restricted Rotation of B-Ring of 2′-Methoxy Flavones by 2D-Noesy in Conjunction with Asis”, Spectroscopy letters, vol. 24, pp. 1047–1057, 1991.