Duddeck, Helmut: Molecular Structures in Three Dimensions

Shikimic Acid Pathway

“…However, 13 C NMR spectrum of (1) does not show the presence of the tautomers (1a) or (1b), as it shows the absence of any downfield carbonyl beyond coumarin carbonyl (~δ 160-162). Perhaps the population of (1a) and (1b) in the above equilibrium is too less to be detected under the condition of the spectral measurement.…”

“…1 H and 13 C NMR: When the pyrone part of the coumarin nucleus is unsubstituted, H3 and H4 appear as a pair of clean doublets at (δ 61-6.4) and (δ 7.3-8.5), respectively, with coupling constants (9.5-10 Hz) in their 1 H NMR spectra. The above ranges cover the substitution effect (e.g., a OCH 3 at C5 causes the downfield shift of H4 because of the C5-O bond anisotropic effect appears at a lower field).…”