The absolute configuration of anti-Vibrio citrinin dimeric derivative by VCD, ECD and NMR methods

Abstract

Citrinin dimeric derivatives are bioactive polyketides previously reported from Penicillium, Aspergillus, and Monascus fungi species. Due to the large distance between the stereogenic centers of the two monomer units, it was difficult to determine the absolute configuration of the whole molecule (1). In previous work, the absolute configuration of 1 was just proposed by biogenetic considerations. To address this problem, the experimental VCD of 1 was compared with the corresponding DFT calculations for two diastereomers (1a and 1b). Also, the experimental ECD and NMR spectra of 1 were combined for analysis with the corresponding theoretical predictions for different diastereomers. Additionally, compound 1 showed promising anti-Vibrio activity against pathogenic Vibrio spp.with MIC values ranging from 0.4 to 0.8 μM.

Structure Revision and Protein Tyrosine Phosphatase Inhibitory Activity of Drazepinone

“…Similarly, the HMBC correlations from H-14 (δ H 1.29) to C-3 (δ C 150.5), and from H-15 (δ H 1.65) to C-4 (δ C 126.3), which represent uncommon four-bond and five-bond correlations, respectively, were not taken into consideration for the proposed structure of drazepinone. To further confirm the above deduction, 13 C NMR chemical shift calculation based on the gauge-independent atomic orbital (GIAO) [7] was performed for the proposed structure of drazepinone at the level of B3LYP/6-311G+(d,p). Unfortunately, a very low correlation coefficient (R 2 ) of 0.9492 was given for the proposed structure (Figure 3).…”

“…Compounds (+)-1 and (−)-1 were isolated as white amorphous substances with the molecular formula C 19 H 19 NO 2 on the basis of their HRESIMS data at m/z 294.1464 [M + H]+ ion. The 1 H and 13 C NMR data of (+)-1 and (−)-1 (Tables 1 and S1) displayed three methyls, nine methines including seven aromatic carbons, and seven non-protonated carbons. These findings were in agreement with 1D NMR and MS data reported for drazepinone [2].…”

“…By the rapid development of modern strategies and methods for structural elucidation, DFT calculations of 13 C chemical shifts and chiral spectra proved to be critical in several profile structure revisions and have greatly facilitated the reliable determination of natural products with undescribed structures [5,6]. In the present work, we thus tried to definitively By the rapid development of modern strategies and methods for structural elucidation, DFT calculations of 13 C chemical shifts and chiral spectra proved to be critical in several profile structure revisions and have greatly facilitated the reliable determination of natural products with undescribed structures [5,6].…”

“…By the rapid development of modern strategies and methods for structural elucidation, DFT calculations of 13 C chemical shifts and chiral spectra proved to be critical in several profile structure revisions and have greatly facilitated the reliable determination of natural products with undescribed structures [5,6]. In the present work, we thus tried to definitively By the rapid development of modern strategies and methods for structural elucidation, DFT calculations of 13 C chemical shifts and chiral spectra proved to be critical in several profile structure revisions and have greatly facilitated the reliable determination of natural products with undescribed structures [5,6]. In the present work, we thus tried to definitively determine the structure of drazepinone by detailed analysis of 2D NMR data and quantum-mechanics-based computational studies of 13 C chemical shifts, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) of (+)-1 and (−)-1.…”

“…In the present work, we thus tried to definitively By the rapid development of modern strategies and methods for structural elucidation, DFT calculations of 13 C chemical shifts and chiral spectra proved to be critical in several profile structure revisions and have greatly facilitated the reliable determination of natural products with undescribed structures [5,6]. In the present work, we thus tried to definitively determine the structure of drazepinone by detailed analysis of 2D NMR data and quantum-mechanics-based computational studies of 13 C chemical shifts, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) of (+)-1 and (−)-1. Here we report a definitive revision of the structures of (+)-1 and (−)-1 and also describe their PTP inhibitory activity.…”