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#53 2,4-DMA

2,4-DIMETHOXYAMPHETAMINE

SYNTHESIS: To a solution of 10 g 2,4-dimethoxybenzaldehyde in 50 mL nitroethane there was added 0.5 g anhydrous ammonium acetate, and the mixture was heated on the steam bath for 2 h. The excess solvent/reagent was removed under vacuum, and the residue oil dissolved in 25 mL boiling MeOH. On cooling, this deposited yellow crystals of 1-(2,4-dimethoxyphenyl)-2-nitropropene that, after filtering, MeOH washing, and air drying, weighed 10.2 g and had a mp of 78-79 °C.

A magnetically stirred suspension of 6.0 g LAH in 300 mL anhydrous Et2O was brought up to a gentle reflux under a He atmosphere. A total of 8.5 g 1-(2,4-dimethoxyphenyl)-2-nitropropene was introduced into the reaction mixture by allowing the condensed Et2O to leach it from a modified Soxhlet condenser. After the addition was complete, the reaction was held at reflux for an additional 24 h. After cooling with an external ice bath, the excess hydride was destroyed by the cautious addition of H2O. When the exothermic reaction had subsided, there was added 500 mL H2O, 150 g potassium sodium tartrate, and sufficient base to bring the pH above 9. The phases were separated, the organic phase dried over anhydrous MgSO4, the drying agent removed by filtration, and the clear filtrate then saturated with anhydrous HCl gas to produce white crystals of 2,4-dimethoxyamphetamine hydrochloride (2,4-DMA) with a mp of 146-147 °C.

DOSAGE: greater than 60 mg.

DURATION: short.

QUALITATIVE COMMENTS: (with 60 mg) This is definitely threshold, or even a bit more. There is a lot of amphetamine-like component, and a certain blush of euphoria. There is also a diffusion of association, so it's more than just amphetamine, no question about it. At the three-hour point, it is definitely quieting down.

EXTENSIONS AND COMMENTARY: What can one say as to the active dosage of 2,4-DMA? Nothing. What can one say as to the duration? Probably short. The 60 milligram report given above is the highest level that I personally know of having been tried in man, and there is no hint as to what might be found at a fully active dose, or just where that dose might be. It might be fully speedy. It might be fully psychedelic. It might give a cardiovascular push that would be scary. Studies of 2,4-DMA on vascular strips (associated with serotonin action) were not impressive in comparison with structurally related psychedelics, and it seems as if its action might involve norepinephrine release. It is a reasonable guess that there would be cardio-vascular activity at higher levels. But it will only be with human trials, someday, that the answer will be known for sure.

The meta-orientation of the two methoxyl groups does, however, greatly increase the susceptibility of the aromatic ring to electrophilic attack. This is one of the three possible meta-dimethoxy substituted amphetamines, and it is the best studied one in the pursuit of potential radio-halogen substituted brain blood-flow agents. This strategy is discussed under IDNNA; the other two meta-compounds are discussed under 3,4-DMA.

The homologues of 2,4-DMA that were iodinated (or occasionally fluor-inated) were mono- or di-alkylated on the nitrogen, and the precursor that was common to all was the corresponding acetone. The above nitrostyrene, 1-(2,4-dimethoxyphenyl)-2-nitropropene, was reduced in acetic acid with elemental iron, and the base-washed extracts stripped of solvent and distilled (125-145 °C at 0.5 mm/Hg) to give 2,4-dimethoxyphenylacetone as a water-white oil. The principal reductive amination product of this, the one that was most thoroughly explored with various halogenation schemes, was obtained by the reaction of 2,4-dimethoxyphenylacetone with dimethylamine and sodium cyanoborohydride. This product, 2,4-dimethoxy-N,N-dimethylamphetamine or 2,4-DNNA, distilled at 105-115 °C at 0.4 mm/Hg and formed a perchlorate salt that melted at 98-98.5 °C. This could be iodinated with the radio-iodide anion, when oxidized with chloramine-T in buffered sulfuric acid, to give the iodinated analogue (2,4-dimethoxy-N,N-dimethyl-5-iodoamphetamine) in an excellent yield. Radio-fluorination with acetyl hypofluorite gave the 5-fluoroanalogue (2,4-dimethoxy-N,N-dimethyl-5-fluoroamphetamine) in an acceptable yield. Both compounds went into a rat's brain to a pretty good extent, but both of them washed out too rapidly to be clinically interesting.

A large family of other N-substituted homologues of 2,4-DMA were similarly prepared from the above ketone and sodium cyanoborohydride. Methylamine, ethylamine, propylamine, isopropylamine and hexylamine gave the corresponding N-alkyl homologues. The N,N-diethyl homologue was made from the primary amine, 2,4-DMA itself, with acetaldehyde and sodium cyanoborohydride but the product, N,N-diethyl-2,4-dimethoxyamphetamine, could not be converted into a crystalline hydrochloride salt.

Yet another variation on these structures was launched, again with the design of making radio-iodination targets which are not psychedelic and thus might be useful clinically. In this variation, the nitrogen atom substitution pattern was held constant, with two methyl groups, as were the ring locations of the two oxygen atoms. But the identities of the alkyl groups on these oxygen atoms were varied. The synthetic procedure followed was to make the appropriate 2,4-dialkoxybenzaldehyde, convert it to the nitrostyrene with nitroethane, reduce this to the phenylacetone with elemental iron, and then reductively aminate this ketone with dimethylamine. Following this reaction scheme, five amphetamine homologues of 2,4-DMA were made, three with the 4-methoxy group maintained but the 2-position extended, and two with both groups extended symmetrically. These are: (1) N,N-dimethyl-2-ethoxy-4-methoxyamphetamine; (2) 2-(n)-butyloxy-N,N-dimethyl-4-methoxy-amphetamine; (3) 2-(n)-decyloxy-N,N-dimethylamphetamine; (4) 2,4-diethoxy-N,N-dimethylamphetamine; and (5) N,N-dimethyl-2,4-di-(i)-propoxyamphetamine. I believe that most of these have been iodinated and assayed in rats, and several of them appear quite promising. But none of them have been assayed in man, yet. The bromination product of 2,4-DMA (5-bromo-2,4-dimethoxyamphetamine, 5-Br-2,4-DMA) is way down in activity (see its recipe, separately). Since all iodo analogues are of about the same potency as the bromo counterparts, and since the addition of two methyl groups on the nitrogen does not appear to enhance central activity, I feel the iodination products of these N,N-dialkyl-dialkoxyamphetamines would not have any interesting psychopharmacology.

There is something vaguely counterproductive, in my evaluation of things, when the goal of a research project is to avoid activity rather than to create it. Although this chemistry was completely fascinating and could have produced the world's best positron-emitting, brain-scanning diagnostic compound, I feel it quite unlikely that it would have produced the world's best insight-revealing, empathy-enhancing psychedelic, so this research direction never totally caught my fancy. I went on to other things.

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