Synthesis and biological comparison of enantiomers of mepenzolate bromide, a muscarinic receptor antagonist with bronchodilatory and anti-inflammatory activities

Abstract

Chronic obstructive pulmonary disease (COPD) is characterized by abnormal inflammatory responses and airflow limitations. We recently proposed that the muscarinic antagonist mepenzolate bromide (mepenzolate) would be therapeutically effective against COPD due to its muscarinic receptor-dependent bronchodilatory activity as well as anti-inflammatory properties. Mepenzolate has an asymmetric carbon atom, thus providing us with the opportunity to synthesize both of its enantiomers ((R)- and (S)-mepenzolate) and to examine their biochemical and pharmacological activities. (R)- or (S)-mepenzolate was synthesized by condensation of benzilic acid with (R)- or (S)-alcohol, respectively, followed by quaternization of the tertiary amine. As predicted by computational simulation, a filter-binding assay in vitro revealed that (R)-mepenzolate showed a higher affinity for the muscarinic M3 receptor than (S)-mepenzolate. In vivo, the bronchodilatory activity of (R)-mepenzolate was superior to that of (S)-mepenzolate, whereas anti-inflammatory activity was indistinguishable between the two enantiomers. We confirmed that each mepenzolate maintained its original stereochemistry in the lung when administered intratracheally. These results suggest that (R)-mepenzolate may have superior properties to (S)-mepenzolate as a drug to treat COPD patients given that the former has more potent bronchodilatory activity than the latter.

Identification of Mepenzolate Derivatives With Long-Acting Bronchodilatory Activity

“…for C 30 H 34 NO 4 (M + ): 472.2482; found: m/z = 472.2488; HPLC: t R (min) = 9.26 (99%). This is a known compound whose 1 H-NMR spectrum was similar to that previously reported as ( R )- MP-GC ( Yamashita et al, 2014 ).…”

“…The precursor of hybrid compound ( pre-Hyb ) was synthesized by the condensation of carboxylic acid ( BA or CA ) and amino-alcohol ( PR, PP , or QC ). The each final quaternary salt of hybrid compounds ( MP-GC, GC-MP, MP-AD ) was prepared as described previously ( Yamashita et al, 2014 ), with some modifications (see below). Column chromatography was performed using Silica gel 60N (Kanto Chemical, Co., Tokyo, Japan).…”

“…The filter-binding assay was performed as described previously ( Yamashita et al, 2014 ), with some modifications. Membrane fractions prepared from Chinese Hamster Ovary (CHO)-K1 cells expressing human muscarinic M2 receptor (hM 2 R) or hM 3 R (Membrane Target Systems, Perkin-Elmer Life and Analytical Sciences, Boston, MA, United States; protein concentration, 8 μg/well) were incubated with 2 nM [ 3 H]NMS ( N -methyl-[ 3 H]-scopolamine methylchloride) (85.5 Ci/mmol) at room temperature for 2 h in 200 μL PBS in the presence of each compound.…”

“…The radioactivity remaining on the filter was monitored with a MicroBeta Trilux microplate scintillation counter (PerkinElmer Life and Analytical Sciences, Boston, MA, United States). Affinities at equilibrium were determined as antagonist dissociation constant ( K i) values after correcting the experimentally determined IC 50 values with the experimentally determined K d value of NMS for hM 2 R or hM 3 R and the concentration of NMS, as described previously ( Yamashita et al, 2014 ). Shown values are an average of at least two independent experiments.…”

Visible-light photoredox-catalyzed umpolung carboxylation of carbonyl compounds with CO2

“…Moreover, as shown in Fig. 1 , the product 4a could be readily converted into valuable anticholinergic drugs trospium chloride (Sanctura) 24 , 27 , mepenzolate bromide (Cantil) 23 , and benactyzine 29 . The α-hydroxycarboxylic acid 4r is also a synthetic precursor for the drugs tiotropium bromide (Spiriva) and aclidinium bromide (Tudorza) 28 .…”