Abstract
From the marine-derived fungus Penicillium sumatrense (Trichocomaceae), a pair of enantiomers [(+)-1 and (−)-1] were isolated with identical 1D NMR data to drazepinone, which was originally reported to have a trisubstituted naphthofuroazepinone skeleton. In this study, we confirmed the structures of the two enantiomers as drazepinone and revised their structures by detailed analysis of extensive 2D NMR data and a comparison of the calculated 13C chemical shifts, ECD, VCD, and ORD spectra with those of the experiment ones. (+)-1 and (−)-1 were evaluated for their PTP inhibitory activity in vitro. (−)-1 showed selective PTP inhibitory activity against PTP1B and TCPTP with IC50 values of 1.56 and 12.5 μg/mL, respectively.
Highlights
Without the assistance of single-crystal X-ray diffraction analysis, many complex natural products that exhibited important biological activities and played a major role in drug discovery were assigned to erroneous structures or could not be unambiguously established [1]
Detailed analysis of 13C NMR data of (+)-1 and (−)-1, it was strangely found that the chemical shift of C-2 with value of δC 102.2 (DMSO-d6)/105.3 (CD3OD)/103.9 (CDCl3) were much lower than what was expected, and the 13C NMR chemical shift calculation of (+)-1 showed that this phenomenon was entirely possible, which was caused by a combination of oxygen and double bond
Column chromatography was performed on Silica gel 200–300 and 300–400 mesh, and Sephadex LH-20 18−110 μm
Summary
Without the assistance of single-crystal X-ray diffraction analysis, many complex natural products that exhibited important biological activities and played a major role in drug discovery were assigned to erroneous structures or could not be unambiguously established [1]. Detailed analysis of 13C NMR data of (+)-1 and (−)-1, it was strangely found that the chemical shift of C-2 with value of δC 102.2 (DMSO-d6)/105.3 (CD3OD)/103.9 (CDCl3) were much lower than what was expected, and the 13C NMR chemical shift calculation of (+)-1 showed that this phenomenon was entirely possible, which was caused by a combination of oxygen and double bond. Detailed analysis of 13C NMR data of (+)-1 and (−), it was strangely found that the chemical shift of C-2 with value of δC 102.2 (DMSOd6)/105.3 (CD3OD)/103.9 (CDCl3) were much lower than what was expected, and the 13C NMR chemical shift calculation of (+)-1 showed that this phenomenon was entirely possible, which was caused by a combination of oxygen and double bond. H-bonds could make the interaction between (−)-1 and PTP1B/TCPTP stronger than that between (+)-1 and PTP1B/TCPTP
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