title: Absolute configurations of fungal and plant metabolites by chiroptical methods. ORD, ECD, and VCD studies on phyllostin, scytolide, and oxysporone.
abstract: The absolute configuration (AC) of the bioactive metabolites phyllostin (1) and scytolide (2), two hexahydro-1,4-benzodioxines produced by Phyllosticta cirsii, and oxysporone (3), a dihydrofuropyranone recently isolated from a strain of Diplodia africana, has been assigned by computational analysis of their optical rotatory dispersion (ORD), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) spectra. Computational prediction of ORD, ECD, and VCD allowed us to assign (3S,4aR,8S,8aR) AC to naturally occurring (-)-1, while (4aR,8S,8aR) AC was assigned to (-)-2 employing only ECD and VCD, because in this case ORD analysis turned out to be unsuitable for AC assignment. Theoretical prediction of both ORD and ECD spectra of 3 led to assignment of (4S,5R,6R) AC to (+)-3. In this case a satisfactory agreement between experimental and calculated VCD spectra was obtained only after taking into account solvent effects. This study shows that in the case of flexible and complex natural products only a concerted application of more than a single chiroptical technique permits unambiguous assignment of absolute configuration.
authors: Dipartimento di Scienze, Università della Basilicata, Via dell'Ateneo Lucano, 10, 85100 Potenza, Italy.
authors: Giuseppe
authors: G
authors: Mazzeo
authors: Ernesto
authors: E
authors: Santoro
authors: Anna
authors: A
authors: Andolfi
authors: Alessio
authors: A
authors: Cimmino
authors: Pavle
authors: P
authors: Troselj
authors: Ana G
authors: AG
authors: Petrovic
authors: Stefano
authors: S
authors: Superchi
authors: Antonio
authors: A
authors: Evidente
authors: Nina
authors: N
authors: Berova
mesh_terms: D001203:Ascomycota / Q000737:chemistry*; D001688:Biological Products / Q000737:chemistry*; D002942:Circular Dichroism; D004146:Dioxanes / Q000737:chemistry*; D005663:Furans / Q000737:chemistry*; D006574:Heterocyclic Compounds, 2-Ring / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009905:Optical Rotatory Dispersion / Q000379:methods*; D013237:Stereoisomerism; D014732:Vibration
chemical_list: D001688:Biological Products; D004146:Dioxanes; D005663:Furans; D006574:Heterocyclic Compounds, 2-Ring; C582586:oxysporone; C582585:scytolide; C528234:phyllostin