Tertiary (2-haloethyl)amine derivatives of the muscarinic agent McN-A-343, [4-[[N-(3-chlorophenyl)carbamoyl]oxy]-2-butynyl]trimethylammonium chloride

Abstract

4-[(2-Chloroethyl)methylamino]-2-butynyl N-(3-chlorophenyl)carbamate (2) and 4-[(2-bromoethyl)methylamino]-2-butynyl N-(3-chlorophenyl)carbamate (3) were synthesized. Compounds 2 and 3 cyclized at neutral pH to an aziridinium ion (4). The rate constants for the cyclization of 2 and 3 at 37 degrees C were about 0.01 and 0.4 min-1, respectively, as measured by titrimetric analysis and by 1H NMR spectroscopy. The aziridinium ion had 1/4 the potency of McN-A-343 (1) as a ganglionic muscarinic stimulant in the anesthetized, pentolinium-treated rat but showed no muscarinic effects on the isolated guinea pig ileum. It caused alkylation of muscarinic receptors in homogenates of the rat cerebral cortex. An irreversible blockade of central muscarinic receptors was also observed after intravenous administration of 3 to mice. Because of its selectivity, irreversible actions, and ability to pass into the central nervous system, 3 should become a valuable tool in studies of muscarinic receptors.

Investigating the interaction of McN-A-343 with the M2 muscarinic receptor using its nitrogen mustard derivative

“…Similar results were observed in homogenates of the rat cerebral cortex that had been previously treated with cyclized BR384 and washed [15]. Our results show that BR384 binds covalently with the M 2 muscarinic receptor presumably through the reaction of the aziridinium ion with a nucleophile on the receptor.…”

“…This compound has been shown to elicit immediate sympathetic effects on the cardiovascular system in vivo and bind irreversibly with muscarinic receptors, causing a long lasting inhibition of muscarinic responses [15]. In the present report, we describe a characterization of the interaction of BR384 with the human M 2 muscarinic receptor.…”

“…The concentration of the aziridinium ion is not constant during the incubation, but decays exponentially from its peak concentration according to the following equation:$$X=X_0{e}^{-t/{\tau }_x}$$in which X 0 denotes the concentration of the aziridinium ion at the start of the incubation and τ x denotes the time constant for the decay of the aziridinium ion. The value of τ x was estimated at 14.3 min by nonlinear regression analysis of the data reported by Ringdahl [15] for the solvolysis of the aziridinium ion in aqueous solution at pH 7.4. A time constant is used to describe the observed decay of the aziridinium ion from its peak concentration to distinguish it from the two fundamental rate constants for the formation ( k f ) and decay ( k d ) of the aziridinium ion.…”

“…The solution was immediately placed on ice and used as soon as possible. The formation of the aziridinium ion was measured previously by 1 H NMR, and the rate constants for formation ( k f , 0.24 ± 0.01 min −1 ) and decay ( k d , 0.099 ± .012 min −1 ) of the aziridinium reported [15]. The peak concentration of the aziridinium ion forms at approximately 6.3 min at 37 °C and represents 54% of the initial parent mustard concentration.…”

“…Amitriptyline, G418 disulfate salt, NMS, WIN 51,708, atropine, acetylcholine perchlorate gallamine, HEPES, CHES, EDTA, scopolamine, sodium thiosulfate and our initial supply of McN-A-343 were from Sigma-Aldrich, St. Louis, MO. Additional McN-A-343 was synthesized as described previously [20], and N-methylamitriptyline, BR384 and its hydrolysis product were synthesized as described by Suga et al [13] and Ringdahl et al [15], respectively. The reactants for organic synthesis were obtained from Sigma-Aldrich.…”