The Characterization of Complex Phenols by Nuclear Magnetic Resonance Spectra

Abstract

The characterization of complex phenols may be aided by comparing the n.m.r. spectrum of the phenol with that of its anion. The chemical shifts of the aromatic protons of the anion in deuterium oxide solution occur at higher field than those of the phenol in deuteriochloroform by characteristic amounts. Phenols bearing only alkyl or alkoxyl substituents show the following upfield changes: ortho, 0.16-0.28 p.p.m.; meta, 0.05-0.11 p.p.m.; para, 0.32-0.39 p.p.m. Comparison in dimethyl sulfoxide solution leads to these ranges: ortho, 0.42-0.59; meta, 0.19-0.38; para, 0.71-0.79 p.p.m. Phenols bearing other substituents may be characterized by study of appropriate models. Conversion to the acetate produces less explicit downfield changes.

Microbial transformation of N-methylcolchiceinamide

“…Attempts were also made to further confirm these assignments by evaluating the upfield shift of the C4-aromatic proton upon the addition of base. It was anticipated that the upfield shift caused by the ortho phenolate of VII would be greater than that caused by the meta phenolate of VI (6,9). Sufficient material for definitive results was only available in the case of VI, but the anticipated shift of 0.31 ppm was observed, consistent with a meta-phenol (6,9).…”

“…It was anticipated that the upfield shift caused by the ortho phenolate of VII would be greater than that caused by the meta phenolate of VI (6,9). Sufficient material for definitive results was only available in the case of VI, but the anticipated shift of 0.31 ppm was observed, consistent with a meta-phenol (6,9). The chromatographic behavior was also consistent with the corresponding phenols of colchicine.…”

“…The upper metabolite (16 mg) gave the following NMR spectrum: (CDC13) ppm (multiplicity, assignment) 1.96 (s, 3H, COCH3), 2.1-2.6 (m, 5H, aliphatics), 3.12 (d, J = 6, 3H, N-CH3), 3.63 (s, 3H, Cl-OCH3) 3.92 (s, 3H, C3-OCH3), 4.74 (broad s, 1H, NH-CH3), 5.90 (broad s, 1H, C2-OH), 6.54 (s, 1H, H-4), 6.60 (d, J = 11, 1H, H-11), 7.50 (d, J = 11, 1H, H-12), 7.63 (s, 1H, H-8), 8.61 (s, 1H, NHCO). In dimethyl sulfoxide-D6 the following partial spectrun was obtained: 6.56 (d, J = 11, 1H, H-11), 6.66 (s, 1H, H-4), 7.11 (s, 1H, H-8), 7.24 (d, J = 11, 1H, H-12); addition of 1.5 eq of NaOH (9) gave the following shifted spectrum: 6.37 (s, 1H, H-4), 6.52 (d, J = 11, 1H, H-11), 7.13 (s, 1H, H-8), 7.32 (d, J = 11, 1H, H-12).…”

“…In dimethyl sulfoxide-D6 the following partial spectrun was obtained: 6.56 (d, J = 11, 1H, H-11), 6.66 (s, 1H, H-4), 7.11 (s, 1H, H-8), 7.24 (d, J = 11, 1H, H-12); addition of 1.5 eq of NaOH (9) gave the following shifted spectrum: 6.37 (s, 1H, H-4), 6.52 (d, J = 11, 1H, H-11), 7.13 (s, 1H, H-8), 7.32 (d, J = 11, 1H, H-12).…”

Cancentrine. II. The Structure of Cancentrine

“…spectra of cancentrine and its 0-acetate led to the conclusion that the phenolic function is para to the aromatic proton appearing at lowest field (9). It follows that the phenolic -OH group must be located at C-20 in cancentrine.…”