Absolute configuration of tropane alkaloids from Schizanthus species by vibrational circular dichroism.
The absolute configuration (AC) of 6beta-hydroxy-3alpha-senecioyloxytropane (1), 3alpha-hydroxy-6beta-tigloyloxytropane (2), 3alpha-hydroxy-6beta-senecioyloxytropane (3), and 3alpha-hydroxy-6beta-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 (1)H 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 3alpha,6beta-tropanediol derivatives.
Reina
Matías
M
Instituto de Productos Naturales y Agrobiología (IPNA), CSIC, La Laguna, Tenerife, Spain.
Burgueño-Tapia
Eleuterio
E
Bucio
María A
MA
Joseph-Nathan
Pedro
P
D000470:Alkaloids / Q000737:chemistry* / Q000302:isolation & purification; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D019657:Solanaceae / Q000737:chemistry*; D014326:Tropanes / Q000737:chemistry* / Q000302:isolation & purification
D000470:Alkaloids; D014326:Tropanes