Antidepressant agents secondary amines

As noted earlier, most classical antidepressant agents consist of propylamine derivatives of tricyclic aromatic compounds. The antidepressant molecule tametraline is thus notable in that it is built on a bicyclic nucleus that directly carries the amine substituent. Reaction of 4-phenyl-l-tetralone (18) (obtainable by Friedel-Crafts cyclization of 4,4-diphenyl butyric acid) with methyl amine in the presence of titanium chloride gives the corresponding Schiff base. Reduction by means of sodium borohydride affords the secondary amine as a mixture of cis (21) and trans (20) isomers. The latter is separated to afford the more active antidepressant of the pair, tametraline (20). 

Partly reduced counterparts of the indole nucleus provide the basis for several agents with varied biological activities. A pair of closely related A-phenyl derivatives have both shown antidepressant activity in test systems. The apparent preference for the monomethyl amine suggests that these act by the same mechanism as the classical tricyclic antidepressants, where the secondary amine is the more active species. The first step in the preparation of the common intermediate (27-3) to these compounds consists of acylation of diphenylamine (27-1) with chloroacetyl chloride. 

HCA is the term is used to refer to both TCAs and analogues of these agents, such as maprotiline and amoxapine. TCAs are by far the most commonly used HCAs and include tertiary amines such as amitriptyline, doxepin, and imipramine and secondary amines such as desipramine and nortriptyline. Most secondary amines could also be viewed as NE-selective antidepressants, while the hallmark of tertiary amine TCAs is their effects on multiple neurotransmitters over their clinically relevant dosing range. 

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