Erkki Rahkamaa

Iodinated melatonin: preparation and characterization of the molecular structure by mass and 1H NMR spectroscopy.

Synthetic melatonin was iodinated by treatment with potassium iodide in the presence of an oxidizing agent, Iodo-Gen. The iodination products of melatonin were extracted with chloroform and separated by HPLC. The fraction showing immunoreactivity with respect to melatonin antisera was characterized as iodomelatonin by mass spectrometry, so that the substitution of iodine had occurred at a ring carbon atom. 1H NMR spectra showed the iodine to be incorporated at the C-2 position of the indole moiety. The N-[2-(2-iodo-5-methoxy-1H-indol-3-yl)ethyl]acetamide (2-iodomelatonin) reported here is more useful than [3H]melatonin as a tracer in melatonin radioimmunoassay. This method offers also the possibility of preparing iodinated serotonin and other indoleamines for biological studies.

1H and13C NMR analysis of some trichothecenes

Abstract1H and13C NMR chemical shifts were determined from the NMR spectra of low concentration solutions of T-2 toxin, T-2 triol, HT-2 toxin, diacetoxyscirpenol, and neosolaniol. Isomerization of neosolaniol was observed to occur in chloroform solution. 1D and 2D1H and13C NMR techniques were used in order to determine the structure of the isomerization product, finally identified as 4β,8α-diacetoxy-3α, 15-dihydroxy-12,13-epoxytrichothec-9-ene.

NMR spectral analysis and molecular dynamics study of 3‐quinuclidinol and 3‐quinuclidinyl benzilate

Proton chemical shifts and coupling constants of 3‐quinuclidinol and 3‐quinuclidinyl benzilate were determined by computer analysis. The relatively broad lines of the quinuclidine protons have their origin in numerous non‐resolved transitions arising from the extensively coupled spin system of 12 nuclei. The signs of the long‐range coupling constants were determined by COSY‐45 and E.COSY. Vicinal coupling constants were converted into proton–proton torsion angles by applying the Altona–Haasnoot equation. Some geometrical ambiguities were revealed, which were studied by molecular dynamics calculations and simulated annealing. The torsion angles and the results from molecular dynamics calculations indicated significant flexibility of the quinuclidine part. For the sake of completeness the carbon chemical shifts of both compounds are presented.