Three Sesquiterpenoid Dimers from Chloranthus japonicus: Absolute Configuration of Chlorahololide A and Related Compounds

Abstract

A novel sesquiterpenoid dimer, named multistalide C (1), together with two known congeners, shizukaols C (2) and D (3), was isolated from the whole plant of Chloranthus japonicus Sieb. The structures of compounds 1-3 were elucidated by extensive HR-ESI-MS, 1D, and 2D NMR spectroscopic analysis. Compounds 1-3 exhibited significant toxic effects on brine shrimp larvae (Artemia salina). The absolute configuration of 1 was established by CD/TDDFT calculations. The related compound chlorahololide A was also reinvestigated. The previous assignment of the absolute configuration of chlorahololide A and several related sesquiterpenoid dimers, based on an incorrect application of the exciton chirality method, is criticized.

Survey of bacteria associated with western corn rootworm life stages reveals no difference between insects reared in different soils

“…Within the Diabrotica species, D. speciosa (Germar), D. balteata LeConte, D. undecimpunctata howardi Barber, and WCR have been studied. D. speciosa is a polyphagous pest attacking several important crops in South America including corn 26 , D. balteata is a pest of sweet potato 26 , and D. undecimpunctata howardi attacks cucurbits and corn 26 . Shalk et al .…”

Exciton coupling between enones: Quassinoids revisited

“…Enone systems appear especially problematic from this viewpoint, because of the many possible sources of ECD signals. [30][31][32] The present case of quassinoids, and a recently reported similar case of chlorahololide A and related sesquiterpenoids, 47 demonstrate that polycyclic bis-enones should be treated with much more attention than one can anticipate. The successful application of ECM to the bis-enone quassin (1) 7 has obviously encouraged its application to several enone-containing systems.…”

Chiroptical and vibrational spectroscopic study of genuine and counterfeit medicines containing tadalafil

“…The first method was the Monte Carlo stochastic sampling with MMFF94 force field, and the second was the systematic search based on the basin-hopping algorithm with MM2 force field implemented in the Tinker molecular modeling software. [34][35][36][37] The solvent effects were considered for all DFT calculations (geometry optimizations and spectra simulations) using the conductor-like polarizable continuum model with the value of the dielectric constant ε = 4.7113 for chloroform and ε = 26.726 for TFE. 33 The obtained low-energy geometries were further re-optimized at the B3LYP/6-31+G(d) level of theory, and from the resulting conformers, only those with relevant Boltzmann weights were selected for further, more refined optimization and simulation of the corresponding spectra at CAM-B3LYP/6-311++G(d,p), M06-2X/6-311++G(d,p), and ωB97X-D/def2TZVP.…”

“…All the selected computational methods had provided solid results in recent studies focused on the determination of the absolute configuration. [34][35][36][37] The solvent effects were considered for all DFT calculations (geometry optimizations and spectra simulations) using the conductor-like polarizable continuum model with the value of the dielectric constant ε = 4.7113 for chloroform and ε = 26.726 for TFE. The final simulated spectra are presented as a Boltzmannweighted average of the spectra of the individual conformers.…”