One of the major goals of research in nuclear medicine is a drug that can be used to demonstrate the brain blood flow pattern. To do this job, a drug should demonstrate four properties. First, it must carry a radioactive isotope that is a positron emitter (best, a fluorine or an iodine atom, for use with the positron camera) that can be put onto the molecule quickly, synthetically, and which will stay on the molecule, metabolically. Second, as to brain entry, the drug should be rapidly and extensively taken up by brain tissue, without being selectively absorbed or concentrated at any specific sites. In other words, it should go where the blood goes. Thirdly, the absorption should be strong enough that it will stay in the brain, and not be washed out quickly. This allows time to both locate and count the radioactivity that was carried in there. And lastly, the drug must be without pharmacological action.

IDNNA looked like a promising candidate when tried with a radioactive iodine label, and there was quite a flurry of interest in using it both as an experimental drug, and as a prototype material for the synthesis of structural variants. It went in quickly, extensively and quite diffusely, and it stayed in for a long time.

But was it pharmacologically active? Here one finds a tricky road to walk. The animal toxicity and behavioral properties can be determined in a straightforward manner. Inject increasing amounts into an experimental animal and observe him closely. IDNNA was quite inert. But, it is a very close analogue to the extremely potent psychedelic , and it is widely admitted that animal assays are of no use in trying to determine this specific pharmacological property. So, a quiet human assay was called for. Since it did indeed go into the brain of experimental animals, it could quite likely go into the brain of man. In fact, that would be a needed property if the drug were to ever become useful as a diagnostic tool.

It was assayed up to levels where would have been active, and no activity was found. So one could state that it had none of the psychedelic properties of DOI at levels where DOI would be active (this, at 2.6 milligrams orally). But you don’t assay much higher, because sooner or later, something might indeed show up. So it can be honestly said, IDNNA is less active than DOI itself, in man. Let’s wave our hands a bit, and make our statement with aggressive confidence. IDNNA has shown no activity in the human CNS at any level that has been evaluated. This sounds pretty good. Just don’t go too far up there, and don’t look too carefully. This is not as unscrupulous as it might sound since, in practical terms, the extremely high specific activities of the radioactive 122I that would be used, would dictate that only an extremely small amount of the drug would be required. One would be dealing, not with milligram quantities, but with microgram quantities, or less.

Some fifteen close analogues of IDNNA were prepared, to see if any had a better balance of biological properties. A valuable intermediate was an iodinated ketone that could be used either to synthesize IDNNA itself or, if it were to be made radio-labelled, it would allow the preparation of any desired radioactive analogue in a single synthetic step. The iodination of p-dimethoxybenzene with iodine monochloride in acetic acid gave 2,5-diiodo-1,4-dimethoxybenzene as white crystals from acetonitrile, with a mp of 167–168 °C. Anal. (C₈H₈I₂O₂) C,H. Treatment of this with an equivalent of butyllithium in ether, followed with N-methyl formanilide, gave 2,5-dimethoxy-4-iodobenzaldehyde as pale yellow crystals from ethanol, with a mp of 136–137 °C. Anal. (C₉H₉IO₃) C,H. This, in solution in nitroethane with a small amount of anhydrous ammonium acetate, gave the nitrostyrene 1-(2,5-dimethoxy-4-iodophenyl)-2-nitropropene as gold-colored crystals from methanol, mp 119–120 °C. Anal. (C₁₁H₁₂INO₄) C,H. This was smoothly reduced with elemental iron in acetic acid to give 2,5-dimethoxy-4-iodophenylacetone as white crystals from methylcyclopentane. These melted at 62–63 °C and were both spectroscopically and analytically correct. Anal. (C₁₁H₁₃IO₃) C,H.

This intermediate, when reductively aminated with dimethylamine, gives IDNNA identical in all respects to the product from the dimethylation of above. But it has also been reacted with 131I NaI in acetic acid at 140 °C for 10 min, giving the radioactive compound by exchange, and this was reductively aminated with over a dozen amines to give radioactive products for animal assay. There was produced in this way, 2,5-dimethoxy-4-iodo-N-alkyl-amphetamine where the alkyl group was , , , , , , , and 3-(dimethylaminopropyl)

3-(dimethylamino)propyl

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. Several dialkyl homologue homologues were made, with the alkyl groups being dimethyl (IDNNA itself), , , and . These specific homologues and analogues are tallied in the index, but a number of other things, such as hydrazine or hydroxylamine derivatives, were either too impure or made in amounts too small to be valid, and they are ignored.

The diethyl compound without the iodine is 2,5-dimethoxy-N,N-diethylamphetamine, which was prepared by the reductive alkylation of with acetaldehyde and sodium cyanoborohydride. This product, , was a clear white oil, bp 82–92 °C at 0.15 mm/Hg which did not form a crystalline hydrochloride. An interesting measure of just how different these N,N-dialkylated homologues can be from the psychedelic primary amines, pharmacologically, can be seen in the published report that the beta-hydroxy derivative of DEDMA is an antitussive, with a potency the same as codeine.

None of these many iodinated IDNNA analogues showed themselves to be superior to IDNNA itself, in the rat model, and none of them have been tasted for their psychedelic potential in man.