A study of the stereochemistry of alkaloids of the galanthamine type by NMR spectroscopy. I
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From a consideration of the spin-spin coupling constants of the protons in the NMR spectra of galanthamine, epigalanthamine, and their acetyl derivatives, is has been established that the OH group in galanthamine is quasi-axial and in epigalanthamine it is quasi-equatorial, and ring B has the half-chair conformation in cis fusion with ring C.
The axial proton at C1 in epigalanthamine gives a signal in a weaker field than the corresponding equatorial proton in galanthamine. The dependence of the chemical shift of the signal of the OH proton in galanthamine on the concentration and the temperature show the existence of an intermolecular hydrogen bond betwen the molecules of the substance in solutions.
KeywordsHydrogen Hydrogen Bond Organic Chemistry Chemical Shift Alkaloid
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