On the spectral properties of tryptamine derivatives

Authors

  • Joaquim Delphino Da Motta Neto,

    1. Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, Florida 32611
    2. Physical Organic Chemistry Group, lab. A622, Departamento de Química Orgǎnica, Instituto de Química da UFRJ, Cidade Universitária, CT, Bloco A, Rio de Janeiro, RJ 21910, Brazil
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  • Ricardo Bicca De Alencastro

    1. Physical Organic Chemistry Group, lab. A622, Departamento de Química Orgǎnica, Instituto de Química da UFRJ, Cidade Universitária, CT, Bloco A, Rio de Janeiro, RJ 21910, Brazil
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Abstract

We report quantum chemical semiempirical calculations of the electronic structure of serotonin (5-hydroxytryptamine, 5-HT) and 5,7-dihydroxytryptamine (5,7-DHT). Those substances are important in the context of Alzheimer's disease. Moreover, the tautomerism of 5,7-DHT, which is not present in serotonin, is also examined. We have found that the phenol form of 5,7-DHT is more stable than is the 4-keto form in the gas phase. However, the large dipole moment of the keto form suggests that a large stabilization of this form can occur in a polar environment, which is confirmed by further supermolecule calculations. We have also calculated the absorption spectra of both 5,7-DHT and serotonin (5-HT) using the INDO/S method at the calculated AM1 geometries, with good agreement with experimental data. Our results give strong support to the hypothesis of the phenol–keto tautomerism of 5,7-DHT being responsible for the UV-visible spectroscopic features. © 1993 John Wiley & Sons, Inc.

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