^abcdOsman R, Mazurek AP, Weinstein H (1987). "Simulation of Molecular Stereoelectronic Mechanism for the Interaction of Hallucinogens and Indole Derivatives at 5-HT Receptors".Steric Aspects of Biomolecular Interactions. CRC Press. pp. 199–210.doi:10.1201/9781351076890-10.ISBN978-1-351-07689-0. Retrieved1 June 2025.FIGURE 3. Structures of some indole derivatives known to act at 5-HT receptors of the lA type: 5-hydroxy-11-aminotetrahydro-benzindole (FHATHBIN); 3,5-secoergolines with or without the 9,10-double bond (ROUSSEL COMPOUNDS); and d-lysergic acid diethylamide (LSD). [...] The importance of the relative position of the 5-HT-like recognition elements at the receptors that we identified in earlier studies, was emphasized by results obtained for two compounds similar to 5-HT but in which the structural elements involved in receptor recognition are positioned differently from 5-HT: 5-hydroxy-11-aminotetrahydrobenzindole (FHATHBIN) in which the position of the side chains is fixed with respect to the indole, and 4(13-aminoethyl)-5-hydroxyindole (FAEFHI) in which the side chain is flexible, and connected to the indole at the C4 position (rather than at C3 as in 5-HT). Ab initio molecular orbital calculations of the molecules and model fragments were performed with structural optimization procedures as described, 20 and the results showed that both structures possess the reactivity elements required for the interaction with the 5-HT receptor. [...] Such is also the basis for the similarity between FHATHBIN and LSD. 20 All these compounds have 5-HT-Iike action on 5-HT receptors.
^abcWeinstein H, Osman R, Topiol S, Ebersole BJ, Mazurek AP (12 March 1984)."Theoretical and experimental studies of drug-receptor interactions: Determinants for recognition of 5-hydroxytryptamine analogs".International Journal of Quantum Chemistry.26 (S11):183–194.doi:10.1002/qua.560260719.ISSN0020-7608. Retrieved1 June 2025.To evaluate the importance of the relative position of the 5-HT-like recognition elements at these receptors, we studied two compounds structurally related to 5-HT in which the structural elements involved in receptor recognition are positioned differently from 5-HT 5-hydroxyaminotetrahydrobenzindole (FHATHBIN) in which the position of the side chain is fixed with respect to the indole, and 4(paminoethyl)-5-hydroxyindole (FAEFHI) in which the side chain is flexible, and connected to the indole at the C4 position (rather than at C3 as in 5-HT). Ab initio molecular orbital calculations of the molecules and model fragments were performed with sTO-3G and 3-2 1 G basis sets, using structural optimization procedures. The results show that both structures possess the reactivity elements required for the interaction with the 5-HT receptor, but that FAEFHI cannot be recognized at the 5-HT receptor because the side chain is held in the wrong conformation with respect to the indole portion by a strong hydrogen bond between the side chain amine group and the hydroxyl at C5. [...] Two new compounds, 5-hydroxyaminotetrahydrobenzindole (FHATHBIN, 2 in Fig. l), and 4-(betu-aminoethyl)-5-hydroxyindole (FAEFHI, 3 in Fig. 1) provide additional opportunity to probe the hypotheses regarding recognition at high affinity 5-HT sites. FHATHBIN incorporates structural elements of the LSD molecule, but has an hydroxyl substituent in the 5-position instead of the C9-C10 double bond, while FAEFHI is an analog of 5-HT in which the aminoethyl side chain was moved from the 3-position of the indole, to the 4-position (see Fig. 1). Preliminary pharmacological data indicated that FHATHBIN had 5-HT-like activity at some receptors in the peripheral nervous system, while FAEFHI did not elicit 5-HT-like activity at concentrations far exceeding those at which 5-HT acted in the same systems [7]. [...] [7] H. P. Weber, SANDOZ, Ltd., private communication.
