Studies on Coumarins, II⁶)

Abstract

The flow of current associated with depolarizations of the giant axon of Loligo has been described in two previous papers (Hodgkin, Huxley & Katz, 1952; Hodgkin & Huxley, 1952). These experiments were concerned with the effect of sudden displacements of the membrane potential from its resting level (V =0) to a new level (V = Vj). This paper describes the converse situation in which the membrane potential is suddenly restored from V = V1 to V = 0. It also deals with certain aspects of the more general case in which V is changed suddenly from V1 to a new value V2. The experiments may be conveniently divided into those in which the period of depolarization is brief compared to the time scale of the nerve and those in which it is relatively long. The first group is largely concerned with movements of sodium ions and the second with movements of potassium ions. METHODS The apparatus and method were similar to those described by Hodgkin et al. (1952). The only new technique employed was that on some occasions two pulses, beginning at the same moment but lasting for different times, were applied to the feedback amplifier in order to give a wave form of the type shown in Fig. 6. The amplitude of the shorter pulse was proportional to V1-V2, while the amplitude of the longer pulse was proportional to V,. The resulting changes in membrane potential consisted of a step of amplitude V1, during the period when the two pulses overlap, followed by a second step of amplitude V,. RESULTS Experiments with relatively brief depotarizations Discontinuities in the sodium current The effect of restoring the membrane potential after a brief period of depolarization is illustrated by Fig. 1. Record A gives the current associated with a maintained depolarization of 41 mV. As in previous experiments, this consisted of a wave of inward current followed by a maintained phase of

Click Chemistry Approach for Bis‐Chromenyl Triazole Hybrids and Their Antitubercular Activity

“…The IR spectrum of triazole adduct 5a – m showed absence of azide band at 2117–2132 per cm, and the 1 H‐NMR spectrum showed two interesting features viz., (i) C 4 ‐CH 2 protons showed a downfield shift and were observed at 6.00 ppm when compared with 4.56 ppm observed in the case of 4‐arylamino methyl 2 H ‐chromen‐2‐one. (ii) The C 3 ‐H of 2 H ‐chromen‐2‐one in the triazole adduct experienced an upfield shift and was observed as a singlet at 5.78 ppm, as against 6.60–6.70 ppm in the case of both 4‐arylaminomehtyl and 4‐phenoxymethyl 2 H ‐chromen‐2‐one (20,28). The observed results are in agreement with our earlier report (18).…”

Facile synthesis of some novel 4-{3-aryl-3, 4-dihydro-2H-benzo[b][1,4] thiazin-2-yl}-2H-chromen-2-one derivatives

“…The required 4-bromomethylcoumarins [18] 1 were prepared by the Pechmann cyclization of various phenols with 4-bromoethylacetoacetate [19]. The o-N -benzylidene thiophenols 2 were prepared by the nucleophilic addition of aromatic aldehydes with o-aminothiophenol.…”

A facile synthesis and evaluation of new biomolecule-based coumarin–thiazoline hybrids as potent anti-tubercular agents with cytotoxicity, DNA cleavage and X-ray studies

“…31 Condensation of 4-bromomethyl coumarin (a-j) (0.01mol) with 4,5-dihydrothiazole-2-thiol (1) (0.01mol) in anhydrous K 2 CO 3 (0.03mol) using absolute ethanol as solvent afforded 4- [(4,5-dihydro-1,3-thiazol-2- providing good to excellent yields (81-91%) as compared to the conventional method (61-75%). 31 Condensation of 4-bromomethyl coumarin (a-j) (0.01mol) with 4,5-dihydrothiazole-2-thiol (1) (0.01mol) in anhydrous K 2 CO 3 (0.03mol) using absolute ethanol as solvent afforded 4- [(4,5-dihydro-1,3-thiazol-2- providing good to excellent yields (81-91%) as compared to the conventional method (61-75%).…”