title: Absolute configurations of phytotoxins seiricardine A and inuloxin A obtained by chiroptical studies.
abstract: The absolute configuration (AC) of the plant phytotoxin inuloxin A, produced by Inula viscosa, and of the fungal phytotoxin seiricardine A, obtained from Seiridium fungi, pathogen for cypress, has been determined by experimental measurements and theoretical simulations of chiroptical properties of three related methods, namely, Optical Rotatory Dispersion (ORD), Electronic Circular Dichroism (ECD), and Vibrational Circular Dichroism (VCD). Computational prediction by Density Functional Theory (DFT) of VCD spectra and by Time-dependent DFT (TDDFT) of ORD and ECD spectra allowed to assign (7R,8R,10S) AC to naturally occurring (+)-inuloxin A. In the case of compound (-)-seiricardine A, which lacks useful for the analysis UV-Vis absorption, and thus provides a hardly detectable ECD spectrum and quite low ORD values, an introduction of a suitable chromophore by chemical derivatization was performed. The corresponding derivative, 2-O-p-bromobenzoate ester, gave rise to an intense ECD spectrum and higher ORD and VCD values. The comparison of computed spectra with the experimental ones allowed to assign (1S,2R,3aS,4S,5R,7aS) AC to (-)-2-O-p-bromobenzoate ester of seiricardine A and then to (-)-seiricardine A. This study further supports a recent trend of concerted application of more than a single chiroptical technique toward an unambiguous assignment of AC of flexible and complex natural products. Moreover, the use of chemical derivatization, with insertion of suitable chromophoric moieties has allowed to treat also UV-Vis transparent molecules by ECD and ORD spectroscopies.
authors.affiliation: Dipartimento di Scienze, Università della Basilicata, via dell'Ateneo Lucano 10, 85100 Potenza, Italy.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Santoro
authors.affiliation: Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mazzeo
authors.affiliation: Department of Life Sciences, New York Institute of Technology (NYIT), 1855 Broadway, New York, NY 10023, USA.
authors.forename: Ana G
authors.initials: AG
authors.lastname: Petrovic
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, Via Cintia 4, 80126 Napoli, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Cimmino
authors.affiliation: JASCO Corporation, Hachioji-shi, Tokyo 192-8537, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Koshoubu
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, Via Cintia 4, 80126 Napoli, Italy. Electronic address: evidente@unina.it.
authors.forename: Antonio
authors.initials: A
authors.lastname: Evidente
authors.affiliation: Department of Chemistry, Columbia University, 3000 Broadway, 3114, New York, NY 10027, USA. Electronic address: ndb1@columbia.edu.
authors.forename: Nina
authors.initials: N
authors.lastname: Berova
authors.affiliation: Dipartimento di Scienze, Università della Basilicata, via dell'Ateneo Lucano 10, 85100 Potenza, Italy. Electronic address: stefano.superchi@unibas.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Superchi
mesh_terms: D000470:Alkaloids; D001688:Biological Products / Q000737:chemistry; D002942:Circular Dichroism; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009905:Optical Rotatory Dispersion; D012717:Sesquiterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D013237:Stereoisomerism; D014732:Vibration
chemical_list: D000470:Alkaloids; D001688:Biological Products; D012717:Sesquiterpenes; C000605023:inuloxin A; C000605024:seiricardine A
keywords: Absolute configuration; Electronic Circular Dichroism; Optical rotation; Phytopathogenic fungi; Phytotoxins; Vibrational Circular Dichroism