Synthesis and characterization of centhaquin and its citrate salt and a comparative evaluation of their cardiovascular actions.

Centhaquin is a compound that produces hypotension and bradycardia in higher doses and resuscitation in lower doses. It is water insoluble, and is unsuitable for intravenous use. We prepared the citrate salt of centhaquin and evaluated its cardiovascular efficacy vs. centhaquin. Centhaquin citrate was prepared and characterized; its purity was determined by HPLC. Mean arterial pressure (MAP), heart rate (HR), pulse pressure (PP), cardiac output (CO), stroke volume (SV) and stroke work (SW) following intravenous administration of centhaquin and the citrate (0.05, 0.15 and 0.45 mg.kg(-1)) were determined in anaesthetized male Sprague-Dawley rats. Centhaquin citrate was 99.8% pure and water soluble. Centhaquin (0.05, 0.15 and 0.45 mg.kg(-1)) produced a maximal decrease in MAP of 15.6, 25.2 and 28.1%, respectively; while centhaquin citrate produced a greater (p<0.001) decrease of 35.7, 47.1 and 54.3%, respectively. The decrease in PP and HR produced by the citrate was greater than centhaquin (p<0.001). At 0.45 mg.kg(-1) centhaquin produced a maximal decrease of 20.9% (p<0.01) in CO, while centhaquin citrate produced a decrease of 42.1% (p<0.001). Reduction in SV (p<0.01) and SW (p<0.001) produced by centhaquin citrate were greater than centhaquin. Centhaquin citrate has greater cardiovascular activity compared to centhaquin.

Synthesis and structural studies of aza analogues of functionalized amino acids: new anticonvulsant agents.

We have reported that functionalized amino acids 1 display potent anticonvulsant activities in mice and rats, and that the activity resides primarily in the D-isomer. In this study we investigated whether selectively replacing the C(2) tetrahedral atom with a trivalent nitrogen provides compounds with comparable activity. Six functionalized N(2)-substituted semicarbazides (3) were prepared. X-ray crystallographic analysis of 1-acetyl-4-benzyl-2-(thiazol-2-yl)semicarbazide (13) showed that it lost asymmetry and adopted a configuration midway between the corresponding D- and L-amino acid derivatives. Evaluation of 3 in both mice (ip) and rats (po) showed that the compounds exhibited significant anticonvulsant activities but in most cases at levels lower than their amino acid counterparts. One of the semicarbazides, 13, displayed excellent activity in mice and rats that compared favorably to that of phenytoin.

The anticonvulsant activities of N-benzyl 3-methoxypropionamides.

We recently reported that the ED50 value for (R,S)-2,3-dimethoxypropionamide (1) in the maximal electroshock (MES)-induced seizure test in mice was 30 mg/kg (Choi, D.; Stables, J.P., Kohn, H. Bioorg. Med. Chem. 1996, 4, 2105). This value is comparable to that observed for phenobarbital (ED50 = 22 mg/kg). Compound 1 is structurally similar to a class of MES-selective anticonvulsant agents, termed functionalized amino acids (2), that were developed in our laboratory. The distinguishing feature of 2 is the differential activities observed for enantiomers. In this study, we asked whether comparable differences in activities were observed in the MES-induced seizure test for (R)- and (S)-1. We developed stereospecific syntheses for these enantiomers and showed that both compounds exhibit nearly equal anticonvulsant activity in mice (i.p.) (MES ED50 = 79-111 mg/kg). The surprisingly high ED50 values for (R)- and (S)-1 required our redetermining the ED50 value for (R,S)-1. We revised this value to 79 mg/kg. A limited structure-activity relationship study for 1 was conducted. Special attention was given to the C(2) methoxy unit in 1. We found that replacement of this moiety led to only modest differences in the MES activities upon ip administration to mice. Significantly, we observed an enhancement in the anticonvulsant activity for (R,S)-N-benzyl 2-hydroxy-3-methoxypropionamide ((R,S)-6) upon oral administration to rats ((R,S)-6: mice (i.p.) ED50 > 100, < 300 mg/kg; rat (oral) ED50 = 62 mg/kg). The activities of 3-methoxypropionamides, functionalized amino acids, and related compounds are discussed.

Development of a gas chromatographic-mass spectrometric drug screening method for the N-dealkylated metabolites of fentanyl, sufentanil, and alfentanil.

A sensitive, specific urinary assay for fentanyl, sufentanil, and alfentanil based on their N-dealkylated metabolites is described. Norfentanyl, norsufentanil-noralfentanil, and 2H5-norfentanyl are synthesized and characterized by standard analytical techniques. Derivatization of these secondary amines to yield the pentafluorobenzamides produces stable products with good gas chromatographic properties and unique, high-mass fragments in their mass spectra. These properties are utilized to develop a drug screening procedure based on gas chromatography-mass spectrometry to detect these major metabolites in human urine. The metabolites are isolated from urine samples by a liquid-liquid extraction procedure. The method allows for detection of metabolite concentrations as low as 0.3 ng/mL.