Novel benzamides as selective and potent gastrokinetic agents. III. Synthesis and structure-activity relationships of 4-amino-5-chloro-2-methoxy- and 2-ethoxy-N-[(4-substituted 2-morpholinyl)methyl]-benzamides

Spectroscopic and structural properties of N-(acetamide) morpholinium bromide

A new crystal of N-(acetamide) morpholinium (NAM) bromide has been prepared in methanol at room temperature and characterized by single crystal X-ray analysis, elemental analysis, GS-MS, FTIR, NMR((1)H,(13)C, DEPTH and HETCOR). The N-(acetamide) morpholinium crystallizes in the orthorhombic crystal system, Pnma with unit cell a=12.798(9) Å, b=7.222(5) Å, c=9.244(5) Å, β=90.00, V=854.4(9) Å(3), Z=4. The X-ray structure determination revealed that there are strong inner and intermolecular hydrogen bonds in the crystal.

Harmonic analysis of vibrations of morpholine-4-ylmethylthiourea: a DFT, midinfrared and Raman spectral study

The FTIR and FT-Raman spectra of morpholine-4-ylmethylthiourea (MMTU) were recorded in the region of mid-IR (400-4,000 cm(-1)). Initial geometry generated from the standard geometrical parameters was relaxed without any constraint on the potential energy surface at MP2 and DFT levels adopting the standard 6-31++G and 6-311+G basis set. With the help of two specific scaling procedures the computed harmonic frequencies have been compared with the observed vibrational wave numbers of FTIR and FT-Raman spectra and assigned to different normal modes of the molecule. Most of the vibrational modes have wave numbers in the expected range. The appropriate theoretical spectrograms of the IR spectra of MMTU have been also constructed.

Measurement of 5-HT4 receptor-mediated esophageal responses by digital sonomicrometry in the anesthetized rat

INTRODUCTION

In vitro studies have demonstrated a 5-HT4 receptor-mediated relaxation of the pre-contracted rat esophagus. However, it is unclear whether 5-HT4 receptor agonists affect resting esophageal tone in vivo. The activity of 5-HT and several well-established 5-HT4 receptor agonists (tegaserod, BIMU-8, cisapride, renzapride, and mosapride) was investigated in a novel in vivo model designed to measure esophageal relaxation using the technique of digital sonomicrometry.

METHODS

Miniature piezo-electric crystals were implanted externally in a longitudinal orientation on the distal esophagus of isoflurane-anesthetized, adult male Sprague-Dawley rats. Measurement of the time for transmission of ultrasonic pulses between the implanted crystals provided a continuous recording of inter-crystal distance and hence esophageal muscle length.

RESULTS

Following cumulative intravenous administration, 5-HT (1-100 microg/kg), tegaserod (1-1000 microg/kg), BIMU-8 (3-3000 microg/kg), renzapride (10-3000 microg/kg), cisapride (30-3000 microg/kg), and mosapride (30-10,000 microg/kg) produced a dose-dependent increase in esophageal inter-crystal distance. The mean ED50 values for tegaserod, BIMU-8, renzapride, cisapride, and mosapride were 11, 49, 51, 141, and 1825 microg/kg, respectively. Pre-treatment with the selective 5-HT4 receptor antagonist, piboserod (SB-207266; 1 mg/kg subcutaneously) significantly attenuated the effects of intravenous tegaserod (1-1000 microg/kg). Following cumulative intraduodenal administration (0.03-10 mg/kg), tegaserod and mosapride exhibited a dose-dependent increase in esophageal inter-crystal distance. The doses associated with a 10% increase in muscle length from the resting level were 2.6 and>10 mg/kg for tegaserod and mosapride, respectively.

DISCUSSION

In conclusion, dose-dependent, 5-HT4 receptor agonist-mediated increases in longitudinal muscle length in the rat esophagus were observed in vivo using the technique of digital sonomicrometry. This in vivo model of esophageal activity may prove useful in evaluating the activity of novel 5-HT4 receptor agonists.

Nitrogen-containing heteroalicycles with serotonin receptor binding affinity: development of gastroprokinetic and antiemetic agents

To obtain gastroprokinetic agents with more potent and selective activity than metoclopramide and cisapride, a series of N-(4-benzyl-2-morpholinylmethyl)benzamides were designed and prepared. Their synthesis and structure-activity relationships were described. As a result, mosapride was selected as a promising candidate for potent gastroprokinetic activity with selective 5-HT4 receptor agonistic activity. As an extension to this project, the novel benzamide and the carboxamide derivatives having 1-benzyl-4-methylhexahydro-1,4-diazepine ring in the amine moiety were prepared and evaluated for 5-HT3 receptor antagonistic activity. DAT-582 was identified as an antiemetic agent in cancer chemotherapy. The asymmetric synthesis of DAT-582 and the SAR studies were briefly reviewed. In further modifications of the N-(1-benzyl-4-methylhexahydro-1,4-diazepin-6-yl)benzamides, the novel nicotinamides with 1-ethyl-4-methylhexahydro-1,4-diazepin ring were found to have potent 5-HT3 and dopamine D2 and D3 receptor antagonistic activities and to show weak central nervous system depression and extrapyramidal syndrome. After extensive SARs, AS-8112 was selected as a broad antiemetic agent.