Terfenadine not only differs from the other antihistamine drugs in its chemical structure, but also in that its action begins within 1-2 h and last approximately 12 h, reaching its peak of action in 3-4 h. It is used for relieving symptoms associated with seasonal allergic rhinitis and conjunctivitis, for angioneurotic edema and allergic skin reaction, and also as an ingredient of complex therapy for bronchial asthma. Synonyms of this drug are sel-dane, hystadin, trexil, and others.
Astemizole: Astemizole, 1-[(4-fluorophenyl)methyl]-N-[1-[2-(4-methoxyphenyl) ethyl]-4-piperidinyl]-benzimidazol-2-amine (16.1.31), is synthesized in a multi-stage synthesis from 1-carbethoxy-4-aminopiperidine and 2-nitroisothiocyanobenzol, from which a derivative of thiourea (16.1.26) is synthesized upon their reaction. The nitro group of the product is reduced and the further S-methoxided. In reaction conditions intermolecular cyclization into a derivative of benimidazol, N-[1-[2-(4-carethoxy)]-4-piperidinyl]benzimidazol-2-amine (16.1.28) occurs. The obtained aminobenzimidazole derivative is alkylated with 4-fluo-robenzylchoride into 1-[(flurophenyl)methyl]-N-[1-[2-(4-carethoxy)]-4-piperidinyl] benzim-idazol-2-amine (16.1.29). The carbethoxyl group of the resulting compound (16.1.29) is hydrolyzed by hydrobromic acid, forming a non-substituted on the nitrogen atom derivative of piperidine (16.1.30), the alkylation of which with 2-(4-methoxyphenyl)ethylmetanesul-fonate leads to the formation of astemizole (16.1.31) [47,48].
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If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.