Clemizole

Clemizole
Clinical data

ATC code	None
Identifiers
IUPAC name 1-[(4-Chlorophenyl)methyl]-2-(pyrrolidin-1-ylmethyl)benzimidazole
CAS Number	442-52-4
PubChem (CID)	2782
ChemSpider	2680
UNII	T97CB3796L^Y
KEGG	D01705
ChEBI	CHEBI:52140
ChEMBL	CHEMBL1407943
NIAID ChemDB	033090
ECHA InfoCard	100.006.486
Chemical and physical data
Formula	C₁₉H₂₀ClN₃
Molar mass	325.84 g/mol
3D model (Jmol)	Interactive image
SMILES Clc1ccc(cc1)Cn3c(nc2ccccc23)CN4CCCC4
InChI InChI=1S/C19H20ClN3/c20-16-9-7-15(8-10-16)13-23-18-6-2-1-5-17(18)21-19(23)14-22-11-3-4-12-22/h1-2,5-10H,3-4,11-14H2 Key:CJXAEXPPLWQRFR-UHFFFAOYSA-N

Clemizole is an H₁ antagonist.

Synthesis

Benzimidazoles substituted with an alkylamine at position 2 have a venerable history as H₁ antihistaminic agents. The standard starting material for many benzimidazoles consists of phenylenediamine, or its derivatives.

Clemizole synthesis:^[1]^[2]

Reaction of that compound with chloroacetic acid can be rationalized by invoking initial formation of the chloromethyl amide. Imide formation with the remaining free amino group closes the ring to afford 2-chloromethyl benzimidazole (3). Displacement of halogen with pyrrolidine affords the alkylation product. The proton on the fused imidazole nitrogen is then removed by reaction with sodium hydride. Treatment of the resulting anion with α,4-dichlorotoluene gives the H₁ antihistaminic agent clemizole (5).

References

↑ Jerchel, D.; Fischer, H.; Kracht, M. (1952). "Zur Darstellung der Benzimidazole". Justus Liebigs Annalen der Chemie. 575 (2): 162. doi:10.1002/jlac.19525750204.
↑ GB 703272 ; M. Schenck, W. Heinz, U.S. Patent 2,689,853 (both 1954 to Schering AG).

Histaminergics

Receptor
(ligands)

H₁	Agonists: 2-Pyridylethylamine Betahistine Histamine HTMT UR-AK49 Antagonists: First-generation: 4-Methyldiphenhydramine Alimemazine Antazoline Azatadine Bamipine Benzatropine (benztropine) Bepotastine Bromazine Brompheniramine Buclizine Captodiame Carbinoxamine Chlorcyclizine Chloropyramine Chlorothen Chlorphenamine Chlorphenoxamine Cinnarizine Clemastine Clobenzepam Clocinizine Cloperastine Cyclizine Cyproheptadine Dacemazine Decloxizine Deptropine Dexbrompheniramine Dexchlorpheniramine Dimenhydrinate Dimetindene Diphenhydramine Diphenylpyraline Doxylamine Embramine Etodroxizine Etybenzatropine (ethylbenztropine) Etymemazine Fenethazine Flunarizine Histapyrrodine Homochlorcyclizine Hydroxyethylpromethazine Hydroxyzine Isopromethazine Isothipendyl Meclozine Medrylamine Mepyramine (pyrilamine) Mequitazine Methafurylene Methapyrilene Methdilazine Moxastine Orphenadrine Oxatomide Oxomemazine Phenindamine Pheniramine Phenyltoloxamine Pimethixene Piperoxan Pipoxizine Promethazine Propiomazine Pyrrobutamine Talastine Thenalidine Thenyldiamine Thiazinamium Thonzylamine Tolpropamine Tripelennamine Triprolidine Second/third-generation: Acrivastine Alinastine Astemizole Azelastine Bamirastine Barmastine Bepiastine Bepotastine Bilastine Cabastinen Carebastine Cetirizine Clemastine Clemizole Clobenztropine Desloratadine Dorastine Ebastine Efletirizine Emedastine Epinastine Fexofenadine Flezelastine Ketotifen Latrepirdine Levocabastine Levocetirizine Linetastine Loratadine Mapinastine Mebhydrolin Mizolastine Moxastine Noberastine Octastine Olopatadine Perastine Pibaxizine Piclopastine Quifenadine (phencarol) Rocastine Rupatadine Setastine Sequifenadine (bicarphen) Talastine Temelastine Terfenadine Vapitadine Zepastine Non-generational: Atypical antipsychotics (e.g., aripiprazole, asenapine, clozapine, iloperidone, olanzapine, paliperidone, quetiapine, risperidone, ziprasidone, zotepine) Tetracyclic antidepressants (e.g., amoxapine, loxapine, maprotiline, mianserin, mirtazapine, oxaprotiline) Tricyclic antidepressants (e.g., amitriptyline, butriptyline, clomipramine, desipramine, dosulepin (dothiepin), doxepin, imipramine, iprindole, lofepramine, nortriptyline, protriptyline, trimipramine) Typical antipsychotics (e.g., chlorpromazine, flupenthixol, fluphenazine, loxapine, perphenazine, prochlorperazine, thioridazine, thiothixene) Unknown/unsorted: Belarizine Elbanizine Flotrenizine Napactadine Tagorizine Trelnarizine Trenizine

H₂	Agonists: Amthamine Betazole Dimaprit Histamine HTMT Impromidine UR-AK49 Antagonists: Bisfentidine Burimamide Cimetidine Dalcotidine Donetidine Ebrotidine Etintidine Famotidine Isolamtidine Lafutidine Lamtidine Lavoltidine (loxtidine) Lupitidine Metiamide Mifentidine Niperotidine Nizatidine Osutidine Oxmetidine Pibutidine Quisultazine (quisultidine) Ramixotidine Ranitidine Roxatidine Sufotidine Tiotidine Tuvatidine Venritidine Xaltidine Zolantidine

H₃	Agonists: α-Methylhistamine Cipralisant Histamine Imetit Immepip Immethridine Methimepip Proxyfan Antagonists: A-349,821 A-423,579 ABT-239 ABT-652 AZD5213 Betahistine Burimamide Ciproxifan Clobenpropit Conessine Enerisant GSK-189,254 Impentamine Iodophenpropit Irdabisant JNJ-5207852 MK-0249 NNC 38-1049 PF-03654746 Pitolisant SCH-79687 Thioperamide VUF-5681

H₄	Agonists: 4-Methylhistamine α-Methylhistamine Histamine OUP-16 VUF-8430 Antagonists: JNJ-7777120 Mianserin Thioperamide Toreforant VUF-6002

Transporter
(inhibitors)

VMATs

TAAR1 inactive	Amiodarone APP AZIK Bietaserpine Deserpidine Dihydrotetrabenazine Efavirenz GBR-12935 GZ-793A Ibogaine Ketanserin Lobeline Methoxytetrabenazine Reserpine Rose bengal SD-809 Tetrabenazine Valbenazine Vanoxerine (GBR-12909)

TAAR1 active	Amphetamine Methamphetamine MDMA Phenethylamine

Enzyme
(inhibitors)

HDC	Catechin Meciadanol Naringenin Tritoqualine

HNMT	Amodiaquine Diphenhydramine Harmaline Metoprine Quinacrine SKF-91,488 Tacrine

DAO	Pimagedine (aminoguanidine)

Others

Precursors	L -Histidine

Cofactors	Vitamin B₆

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Clemizole

Synthesis

See also

References