Involucratusins A-H: Unusual Cadinane Dimers from Stahlianthus involucratus with Multidrug Resistance Reversal Activity

Access to Saturated Oxygen Heterocycles and Lactones via Electrochemical Sulfonylative Oxycyclization of Alkenes with Sulfonyl Hydrazides

A facile electrochemical sulfonylative cycloetherification of linear unsaturated alcohols with sulfonyl hydrazides under mild conditions has been accomplished. This catalyst- and oxidant-free protocol proceeds via electro-oxidation, followed by radical addition, as well as an intramolecular oxygen nucleophilic process. This methodology is compatible with a broad substrate scope and good functional group compatibility, which provides a valuable and convenient synthetic tool for the synthesis of saturated five-, six-, seven-, and eight-membered ring oxygen heterocycles. Furthermore, sulfonylative cycloesterification of linear unsaturated acids toward the lactone products has also been established under this electrochemical system. In addition, control experiments indicated that the N-H bonds of the sulfonyl hydrazide molecule are non-essential.

Cadinane Sesquiterpenoids and Their Glycosides from Alangium chinense That Inhibit Spontaneous Calcium Oscillations

Nine new cadinane sesquiterpenoids, alanenses A-I (1-9), were isolated from the leaves of Alangium chinense together with three previously reported analogues (10-12). The structures of these molecules were elucidated by interpretation of spectroscopic and spectrometric data. Absolute configurations were established by the comparison of experimental and calculated ECD data, chemical degradation studies for sugar moieties, and a single-crystal X-ray diffraction analysis. Compounds 1 and 2 were isolated as racemates, and enantiopurification was achieved by chiral HPLC. Compounds 3-5 are glycosylated cadinanes bearing a β-d-glucose unit, while compounds 6-9 incorporate a hydroxymethyl group in either the free form or additional ring fusion. The structure of compound 11 was originally misassigned and later revised using additional NMR data. The corrected structure is here supported by X-ray single-crystal analysis. Compounds 1 and 2 inhibit spontaneous calcium channel oscillations at low micromolar concentrations.

Bioassay-Guided Isolation and HPLC Quantification of Antiproliferative Metabolites from Stahlianthus Thorelii

In folk medicine, Stahlianthus thorelii Gagnep. has been used to treat diseases related to inflammation, ulcers, and cancer. There are no reports concerning the chemical components and bioactivities of S. thorelii; thus, this study aims to explore the phytochemicals, quantify the main compounds, and test the anticancer activity of isolates from S. thorelii. Dried rhizomes were extracted with 95% ethanol and, then, partitioned, fractionated, and isolated. On the basis of the result of the antiproliferative activity of the fractions, seven isolates were yielded and were identified by spectroscopic analyses. The inhibition of cancer proliferation was determined by an MTT assay and the deployed IC₅₀ to value their efficacy. Seven compounds containing one new C-benzylated dihydrochalcone derivative, thorechalcone A (1) and 2–7 were isolated from S. thorelii. In terms of the bioactivity, compounds 1 and 3 displayed promising antiproliferative activity (WiDr, A549, and HepG2), with IC₅₀ values <40 µM. The HPLC-UV method of quantification of two major compounds (3 and 4) was also validated. This study presented the isolations of antiproliferative potentials of new chalcone and known flavonoid derivatives from S. thorelii. The validated simple, accurate, and rapid HPLC method could be deployed for the quality control of herbal drugs.

Natural disesquiterpenoids: an update

This review highlights the progress on the isolation, bioactivity, biogenesis and total synthesis of dimeric sesquiterpenoids since 2010.

Isolation, Structure Elucidation, and Absolute Configuration of Syncarpic Acid-Conjugated Terpenoids from Rhodomyrtus tomentosa

Three new syncarpic acid-conjugated sesquiterpenoids, tomentodiones E-G (1-3), and six new syncarpic acid-conjugated monoterpenoids, tomentodiones H-M (4-9), were isolated from the leaves of Rhodomyrtus tomentosa. Compounds 1-3 represent the first examples of β-calacorene-based meroterpenoids. Their structures and absolute configurations were determined by a combination of NMR and ECD spectroscopy and X-ray diffraction analysis. On the basis of ECD data analysis for isolated and synthesized compounds, an empirical rule was proposed to determine the absolute configuration at C-7' of syncarpic acid-conjugated terpenoids. Additionally, a study of the reversal effect of multidrug resistance in doxorubicin-resistant human breast cancer cells showed that the noncytotoxic (+)-4 exerted the strongest potentiation effect of doxorubicin susceptibility, with an enhancement of 16.5-fold at a concentration of 30 μM.