The Jalap Roots: A Herbal Legacy from the Neotropics to the World.

Etnopharmacological Relevance: The Convolvulaceae or morning glory family, with about 2000 species in the world's Tropics and subtropics, stands out among the plants used in traditional medicine. Medicinal plant complexes with important purgative properties have been developed in Mexico and Brazil from members of the genera Ipomoea and Operculina with storage roots. Popularly known as the jalap roots, their resin glycosides cause purgative and laxative activities that facilitate bowel movements.

Vicinal 1H-1H NMR coupling constants from density functional theory as reliable tools for stereochemical analysis of highly flexible multichiral center molecules.

A protocol for stereochemical analysis, based on the systematic comparison between theoretical and experimental vicinal (1)H-(1)H NMR coupling constants, was developed and applied to a series of flexible compounds (1-8) derived from the 6-heptenyl-5,6-dihydro-2H-pyran-2-one framework. The method included a broad conformational search, followed by geometry optimization at the DFT B3LYP/DGDZVP level, calculation of the vibrational frequencies, thermochemical parameters, magnetic shielding tensors, and the total NMR spin-spin coupling constants. Three scaling factors, depending on the carbon atom hybridizations, were found for the (1)H-C-C-(1)H vicinal coupling constants: f((sp3)-(sp3)) = 0.