Abstract
Chemical profiling of the Streptomyces sp. strain SUD119, which was isolated from a marine sediment sample collected from a volcanic island in Korea, led to the discovery of three new metabolites: donghaecyclinones A–C (1–3). The structures of 1–3 were found to be rearranged, multicyclic, angucyclinone-class compounds according to nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. The configurations of their stereogenic centers were successfully assigned using a combination of quantum mechanics–based computational methods for calculating the NMR shielding tensor (DP4 and CP3) as well as electronic circular dichroism (ECD) along with a modified version of Mosher’s method. Donghaecyclinones A–C (1–3) displayed cytotoxicity against diverse human cancer cell lines (IC50: 6.7–9.6 μM for 3).
Highlights
Quantum mechanics–based computation is emerging as a useful tool for elucidating the structure of natural products and complements the analysis of experimental spectroscopic data [1,2,3]
Our CP3 calculation—which was specially devised for the assignment of relative configuration to two probability analysis of 2 and 3 along with the experimental and the calculated chemical shift values plausible diastereomers from two sets of experimental nuclear magnetic resonance (NMR) data—was applied instead of DP4 [5]
1 H, 13 C, and 2D NMR spectra were acquired on Bruker Avance 600 MHz and 850 MHz spectrometers (Bruker, Billerica, MA, USA) at the National Center for Inter-University Research Facilities (NCIRF) at Seoul National University
Summary
Quantum mechanics–based computation is emerging as a useful tool for elucidating the structure of natural products and complements the analysis of experimental spectroscopic data [1,2,3]. The recent development of advanced statistical analyses (for example, CP3 and DP4) has enabled us to assign the relative configurations of natural products possessing remote stereogenic centers that are located multiple bonds away from the other chiral centers with assigned configurations These analyses utilize computed 1 H and 13 C NMR chemical shift values based solely on computational methods and statistically compare them with experimental NMR chemical shifts using web-based applets provided by the Smith and Goodman groups [3,5,6]. WeInhave product that structurally aims to discover structurally novel and biologically [10] This been examining chemical profiles actinobacterial that inhabit the marine environments regard, we havethe been examining theofchemical profilesstrains of actinobacterial strains that inhabit the of volcanic islands, which may provide microbial habitats volcanic minerals salts marine environments of volcanic islands, unique which may provide uniquewith microbial habitats withand volcanic from the surrounding seawater [11].
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