43076-30-8Relevant articles and documents
Mechanism of block of a human cardiac potassium channel by terfenadine racemate and enantiomers
Yang,Prakash,Roden,Snyders
, p. 267 - 274 (1995)
1. The cardiac toxicity of racemic terfenadine (marked QT prolongation and polymorphic ventricular arrhythmias) is probably due to potassium channel blockade. To test whether one of its enantiomers would be a less efficient potassium channel blocker, we compared the mechanism of action of the racemate with that of the individual enantiomers. 2. We synthesized the individual enantiomers of terfenadine and examined under whole cell voltage-clamp conditions the mechanism of action of the racemate, both enantiomers and a major metabolite on a cloned human cardiac potassium channel, hKv1.5. This delayed rectifier is sensitive to quinidine, clofilium and other 'class III' antiarrhythmic drugs at clinically relevant concentrations. 3. Upon depolarization, racemic terfenadine and its enantiomers induced a fast decline of hKv1.5 current towards a reduced steady state current level. During subsequent repolarization the tail currents deactivated more slowly than the control, resulting in a 'crossover' phenomenon. 4. The voltage-dependence of block was biphasic with a steep increase in block over the voltage range of channel opening (-30 to 0 mV), and a more shallow phase positive to 0 mV (where the channel is fully open). The latter was consistent with a binding reaction sensing 21% of the transmembrane electrical field (with reference to the cell interior). 5. The EC50 for hKv1.5 block by racemic terfenadine was 0.88 μM, while the values for R- and S-terfenadine were 1.19 μM and 1.16 μM, respectively. In contrast, the acid metabolite reduced hKv1.5 current by only 5% at a concentration of 50 μM. 6. These findings suggest that terfenadine blocks the hKv1.5 channel after it opens by entering into the internal mouth of the channel. We have previously shown that quinidine blocks hKv1.5 in a similar manner but with an apparent affinity of ~6 μM. Thus, terfenadine and its enantiomers are approximately equipotent open state blockers of this human K+ channel and about 6 times more potent than quinidine. The similar state-, time-, and voltage-dependence of hKv1.5 block by both enantiomers also indicates that the chiral centre does not significantly constrain the orientation of critical binding determinants of terfenadine with respect to the receptor site.
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Biooxidation of methyl group: application to the preparation of alcohol and acid metabolites of terfenadine, ebastine and analogues
El Ouarradi, Amane,Salard-Arnaud, Isabelle,Buisson, Didier
experimental part, p. 11738 - 11744 (2009/04/11)
The aim of this study was to found the best conditions to prepare metabolites of terfenadine, ebastine and analogues. For that purpose we investigated the structural substrate requirements needed for the oxidative whole cell activity and selected the most efficient conditions to obtain each compound. Our results showed that either alcohol or acid derivative arising from the oxidation of a methyl group is the main product, ratio depending on the microorganism used and on the culture conditions of cells. The oxidized metabolites were synthesized at preparative scale and isolated in 35-88% yield before characterization.