Ultraviolet absorption spectra: Some substituted coumarins

Masrani, K. V.; Rama, H. S.; Bafna, S. L.

doi:10.1002/jctb.5020240604

Cited by 26 publications

(15 citation statements)

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“…Ultraviolet spectroscopic studies failed to distinguish between the possible tautomeric forms [29,[31][32][33][34][35][36][53][54][55][56][57]. Two model methyl ethers, 4-methoxycoumarin and 2-methoxychromone, both have UV spectra that are blueshifted relative to the spectra of typical 3-subsituted coumarin anticoagulants.…”

Section: Determining Tautomeric Equilibriamentioning

confidence: 99%

“…Karl Paul Link's students took special interest in this problem [26]. Other investigators used chemical reactivity [27][28][29][30], ultraviolet spectroscopy [29,[31][32][33][34][35][36], infrared spectroscopy [29,30,34,[37][38][39][40] and proton nuclear magnetic resonance spectroscopy [40] to probe the 4-hydroxycoumarin-2,4-chromadione-2-hydroxychrome equilibrium. X-ray crystallographic studies confirmed in every case studied up through the early 1970s that, at least in the solid state, the 4-hydroxycoumarin form predominates, based on the bond lengths in the pyranone ring [16,17,[41][42][43][44][45][46][47].…”

Section: Determining Tautomeric Equilibriamentioning

confidence: 99%

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Warfarin: history, tautomerism and activity

Porter

2010

J Comput Aided Mol Des

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The anticoagulant drug warfarin, normally administered as the racemate, can exist in solution in potentially as many as 40 topologically distinct tautomeric forms. Only 11 of these forms for each enantiomer can be distinguished by selected computational software commonly used to estimate octanol-water partition coefficients and/or ionization constants. The history of studies on warfarin tautomerism is reviewed, along with the implications of tautomerism to its biological properties (activity, protein binding and metabolism) and chemical properties (log P, log D, pK (a)). Experimental approaches to assessing warfarin tautomerism and computational results for different tautomeric forms are presented.

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Section: Determining Tautomeric Equilibriamentioning

confidence: 99%

Section: Determining Tautomeric Equilibriamentioning

confidence: 99%

Warfarin: history, tautomerism and activity

Porter

2010

J Comput Aided Mol Des

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“…The reported spectral behaviour has only been for diagnostic purposes and the observed bands were assigned to the benzene and pyrone rings (16,17). The spectra of hydroxycoumarins and many of their derivatives, have been reported (18).…”

Section: Introductionmentioning

confidence: 99%

The electronic absorption spectra of some coumarins. A molecular orbital treatment

Abu‐Eittah¹,

El‐Tawil²

1985

Can. J. Chem.

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The electronic absorption spectra of coumarin and its derivatives umbelliferone (6-hydroxycoumarin), esculetin (6,7-dihydroxycoumarin), and scopoletin (6-methoxy-7-hydroxycoumarin) were investigated. The n → π* transition was not observed in the spectrum of coumarin but was observed in the spectra of some of its derivatives. Molecular orbital calculations, using the INDO procedures, were carried out on coumarin and some of its derivatives. The activities of the different sites of the molecules are discussed in terms of the coefficients of the atomic orbitals constituting the HOMO and the LUMO. The correspondence between the calculated and experimental transition energy and band intensity is satisfactory.

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“…159-160 C. The ESI mass spectra of 1 recorded in the positive and negative ionization modes showed molecular ions at m/z 257 [M þ Na] þ and 233 [M À H] À corresponding to a C 13 H 14 O 4 composition. The UV spectrum had benzopyrone maxima at 248 and 339 nm; IR bands were observed at 1690 cm À1 (pyrone carbonyl) and 3350 cm À1 (OH) [12,13]. The 1 H-NMR spectrum showed an AX system for two ortho coupling aromatic protons at 7.07 and 8.01 ppm (J ¼ 8.6 Hz), a one proton singlet at 6.43 ppm, and a three proton singlet at 3.91 ppm for a methoxy group; the OH appeared as a broad signal at 6.42 ppm.…”

Section: Resultsmentioning

confidence: 99%