Absolute configuration of tropane alkaloids from Schizanthus species by vibrational circular dichroism |
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Authors: | Matías Reina María A Bucio |
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Institution: | a Instituto de Productos Naturales y Agrobiología (IPNA), CSIC, La Laguna, Tenerife, Spain b Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala, Col. Santo Tomás, México, D.F., 11340, Mexico c Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D.F., 07000, Mexico |
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Abstract: | The absolute configuration (AC) of 6β-hydroxy-3α-senecioyloxytropane (1), 3α-hydroxy-6β-tigloyloxytropane (2), 3α-hydroxy-6β-senecioyloxytropane (3), and 3α-hydroxy-6β-angeloyloxytropane (4) was assigned as (1R,3R,5S,6R) using density functional theory (DFT) calculations at the B3LYP/DGDZVP level of theory in combination with experimental vibrational circular dichroism (VCD) measurements and comparison with the spectra of similar tropanes. The AC of 1 followed from a sample isolated from Schizanthus grahamii, while those of the mixture of 2 and 3, isolated from the same source, were determined by comparing the VCD measurement to a weighted calculation of the individual VCD spectra according to a 69:31 ratio of 2:3 determined by 1H NMR signal integration. In turn, Schizanthus pinnatus provided a 7:3 mixture of 1:4 whose AC was determined using the experimental VCD absorptions in the 1150-950 cm−1 spectral region which were compared with those observed for 1-3 and with those described for other 3α,6β-tropanediol derivatives. |
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Keywords: | Schizanthus grahamii S pinnatus Solanaceae Absolute configuration Vibrational circular dichroism 3α 6β-Tropanediol alkaloids Schizanthus species |
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