absolute configuration
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Author(s):  
Shinji Kamisuki ◽  
Hisanobu Shibasaki ◽  
Koudai Ashikawa ◽  
Kazuki Kanno ◽  
Koichi Watashi ◽  
...  

2022 ◽  
Vol 23 (2) ◽  
pp. 909
Author(s):  
Derek R. Boyd ◽  
Narain D. Sharma ◽  
Paul J. Stevenson ◽  
Patrick Hoering ◽  
Christopher C. R. Allen ◽  
...  

Enzymatic oxidations of thiophenes, including thiophene-containing drugs, are important for biodesulfurization of crude oil and drug metabolism of mono- and poly-cyclic thiophenes. Thiophene oxidative dearomatization pathways involve reactive metabolites, whose detection is important in the pharmaceutical industry, and are catalyzed by monooxygenase (sulfoxidation, epoxidation) and dioxygenase (sulfoxidation, dihydroxylation) enzymes. Sulfoxide and epoxide metabolites of thiophene substrates are often unstable, and, while cis-dihydrodiol metabolites are more stable, significant challenges are presented by both types of metabolite. Prediction of the structure, relative and absolute configuration, and enantiopurity of chiral metabolites obtained from thiophene enzymatic oxidation depends on the substrate, type of oxygenase selected, and molecular docking results. The racemization and dimerization of sulfoxides, cis/trans epimerization of dihydrodiol metabolites, and aromatization of epoxides are all factors associated with the mono- and di-oxygenase-catalyzed metabolism of thiophenes and thiophene-containing drugs and their applications in chemoenzymatic synthesis and medicine.


Chemistry ◽  
2022 ◽  
Vol 4 (1) ◽  
pp. 31-41
Author(s):  
Piero Decleva

The sensitivity of Photoelectron Circular Dichroism (PECD) in the angular distribution of photoelectrons, a recent chiral technique, to detect chirality in pure hydrocarbons is investigated in a number of benchmark molecules. It is found that a very large chiral signal is expected, surpassing most current examples, giving a sure fingerprint of absolute configuration. On the other hand, the sensitivity to specific isomers or closely related molecules is relatively modest.


2022 ◽  
Vol 12 ◽  
Author(s):  
Ke Ye ◽  
Xiao Lv ◽  
Xian Zhang ◽  
Pan-Pan Wei ◽  
Zheng-Hui Li ◽  
...  

Five new isopimarane diterpenes, robustaditerpene A-E (1–5), which include 19-nor-isopimarane skeleton and isopimarane skeleton, were isolated from the liquid fermentation of the endophytic fungus Ilyonectria robusta collected from Bletilla striata. The structure elucidation and relative configuration assignments of all compounds were accomplished by interpretation of NMR and HRESIMS spectrometric analyses and 13C NMR calculation. And the absolute configuration of 1-5 were identified by single-crystal X-ray diffraction and ECD calculation. Compound 3 inhibited lipopolysaccharide-induced B lymphocytes cell proliferation with an IC50 value at 17.42 ± 1.57 μM while compound 5 inhibited concanavalin A-induced T lymphocytes cell proliferation with an IC50 value at 75.22 ± 6.10 μM. These data suggested that compounds 3 and 5 may possess potential immunosuppressive prospect.


Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 198
Author(s):  
Jing-Zhe Yuan ◽  
Yi-Ling Yang ◽  
Wei Li ◽  
Li Yang ◽  
Hao-Fu Dai ◽  
...  

Nine new sesquiterpenoids (1–9) were isolated from ethyl ether extract of agarwood originated from Aquilaria sp., including three novel sesquiterpenoids (1–3) derived from zizaane, together with six zizaane-type sesquiterpenoids (4–9). All structures were unambiguously elucidated based on 1D and 2D NMR spectra as well as by HRESIMS data. The absolute configuration of sesquiterpenoids was determined by comparison of the experimental and computed ECD spectra. In vitro anti-inflammatory assessment showed that compound 9 exhibited inhibition of NO production in LPS-stimulated RAW264.7 cells with an IC50 value of 62.22 ± 1.27 μM.


Planta Medica ◽  
2021 ◽  
Author(s):  
Hanli Ruan ◽  
Ying Gao ◽  
Ruihua Mao ◽  
Ye Liu ◽  
Ming Zhou

Two new cytochalasans with a rare 6/6/5/5/7 pentacyclic ring system, named chaetoconvosins C−D (1−2), together with two known congeners (3−4), were isolated from the fermentation of an endophytic fungus, Chaetomium sp. SG-01, harbored in the fibrous roots of Schisandra glaucescens Diels. Their structures including the absolute configuration were elucidated by extensive spectroscopic (HRESIMS, NMR, and ECD) and X-ray crystallographic analyses. The TRAIL sensitivity of 1–4 in a TRAIL-resistant HT29 colorectal cancer cell line was evaluated, which revealed that co-treatment of 1–4 at 50 µM with TRAIL (150 ng/mL) reduced the HT29 cell viability by 19.0%, 24.1%, 17.9%, and 15.5%, respectively, compared to treatment with 1–4 alone.


2021 ◽  
Vol 23 (1) ◽  
pp. 273
Author(s):  
Marcin Górecki ◽  
Jadwiga Frelek

This paper’s main objective is to show that many different factors must be considered when solving stereochemical problems to avoid misleading conclusions and obtain conclusive results from the analysis of spectroscopic properties. Particularly in determining the absolute configuration, the use of chiroptical methods is crucial, especially when other techniques, including X-ray crystallography, fail, are not applicable, or give inconclusive results. Based on various β-lactam derivatives as models, we show how to reliably determine their absolute configuration (AC) and preferred conformation from circular dichroism (CD) spectra. Comprehensive CD analysis, employing both approaches, i.e., traditional with their sector and helicity rules, and state-of-the-art supported by quantum chemistry (QC) calculations along with solvation models for both electronic (ECD) and vibrational (VCD) circular dichroism ranges, allows confident defining stereochemistry of the b-lactams studied. Based on an in-depth analysis of the results, we have shown that choosing a proper chiroptical method/s strictly depends on the specific case and certain structural features.


Marine Drugs ◽  
2021 ◽  
Vol 20 (1) ◽  
pp. 31
Author(s):  
Ohad Hasin ◽  
Shani Shoham ◽  
Yoel Kashman ◽  
Micha Ilan ◽  
Shmuel Carmeli

Theonella swinhoei is a fairly common inhabitant of reefs throughout the Indian and Pacific Oceans. Metabolomic analyses of samples of T. swinhoei collected in different depths in the Gulf of Aqaba revealed two chemotypes differing in the profiles of the theonellamides they produce, some of which seem to be unknown. Driven by this finding, we examined a sample of T. swinhoei collected more than 40 years ago in the southern part of the Gulf of Aqaba. Large-scale extract of this sample yielded four theonellamides, the known theopalauamide (4), as the major component, and three new metabolites, theonellamide J (1), 5-cis-Apoa-theopalauamide (2), and theonellamide K (3), as the minor components. The planar structure of these complex cyclic glycopeptides was elucidated by combination of 1D and 2D NMR techniques and HRESIMS. The absolute configuration of the amino acids was established by Marfey’s and advanced Marfey’s methods, and the absolute configuration of its galactose unit using “Tanaka’s method” for monosaccharides. The biological activity of the pure compounds was tested for antibacterial activity and for cytotoxicity to HTC-116 cell line. The compounds presented significant cytotoxicity against the HTC-116 cell line, illuminating the importance of the Apoa subunit for the activity.


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