摘要
alpha-Pyrones and furanones are metabolites produced by Diplodia corticola, a pathogen of cork oak. Previously, the absolute configuration (AC) of diplopyrone was defined by chiroptical methods and Mosher's method. Using Xray and chiroptical methods, the AC of sapinofuranone C was assigned, while that of the (4S,5S)-enantiomer of sapinofuranone B was established by enantioselective total synthesis. Diplofuranone A and diplobifuranylones A-C ACs are still unassigned. Here electronic and vibrational circular dichroism (ECD and VCD) and optical rotatory dispersion (ORD) spectra are reported and compared with density functional theory computations. The AC of the (45,5S)-enantiomer of sapinofuranone B and sapinofuranone C is checked for completeness. The AC of diplobifuranylones A C is assigned as (2S,2'S,5'S,6'S), (2S,2'R,5'S,6'R), and (2S,2'S,5'R,6'R), respectively, with the Mosher's method applied to define the absolute configuration of the carbinol stereogenic carbon. The AC assignment of sapinofuranones is problematic: while diplofuranone A is (4S,9R), sapinofuranones B and C are (4S,5S) according to ORD and VCD, but not to ECD. To eliminate these ambiguities, ECD and VCD spectra of a di-p-bromobenzoate derivative of sapinofuranone C are measured and calculated. For phytotoxicity studies, it is relevant that all six compounds share the S configuration for the stereogenic carbon atom of the lactone moiety.
- 出版日期2017-9