A group of drugs structurally related to amphetamines that suppress appetite and which are used in treatment of obesity are called analeptics.
Compounds of this group exhibit a range of pharmacological and toxicological action analog to that of amphetamines, and are used as adjuvant drugs in the treatment of obe-sity,which is accomplished through an individually structured program of limiting caloric intake. Not one of the substances used exceeds amphetamines in terms of activity; however, the lesser likelihood of dependence makes its use preferable. The mechanism of action of these drugs is similar to that of amphetamines. They activate satiation centers of the hypothalamus, thus reducing appetite. Anorectics can enhance the effects of narcotics, barbiturates, alcohol, and other CNS depressants.
Phentermine: Phentermine, a,a-dimethylphenylethylamine (8.3.4), differs from amphetamine in the presence of an additional methyl group in the a-position of the amino group. It is synthesized from benzaldehyde, the condensation of which with 2-nitropropane gives carbinol (8.3.1). Reduction of the nitro group of this product gives 2-amino-2-methyl-1-phenylpropanol (8.3.2). The hydroxyl group is replaced with a chlorine atom upon reaction with thionyl chloride, giving 2-amino-2-methyl-1-phenylpropylchloride (8.3.3). Reducing this with hydrogen using a palladium on calcium carbonate catalyst gives phen-termine (8.3.4) [23,24].
CH3 H-C-NOa CH3
Cl CH3 CH3
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