Stereochemistry Of Compounds Research Articles

Megastigmane glycoside and phenol glycosides from the bark of Mallotus barbatus

A new megastigmane glycoside, barbatcoside A (1), and two new phenol glycosides, barbatcosides B (2) and C (3), together with eight known compounds (4-11) were isolated from the bark of Mallotus barbatus Müll. Arg. Their structures were elucidated using extensive 1D and 2D NMR as well as HRESIMS spectroscopic data. The stereochemistry of compounds 1 and 2 were established based on the experimental CD curves. The anti-inflammatory activities of compounds 1-11 from M. barbatus were evaluated using LPS-stimulated RAW 264.7 cell models. Compounds 2 and 3 substantially inhibited the release of NO with IC50 values of 34.78 μM and 20.73 μM, respectively.

Structural elucidation of two new polypropionates from the marine slug Paromoionchis tumidus by spectroscopic analyses and DFT calculations

Tumiduspyrones A and B (1‒2), two new C17 and C18 polypropionates, and three known compounds (3‒5) were isolated from the sea slug Paromoionchis tumidus. Their structures and the absolute configurations of 1 and 2 were elucidated by spectroscopic analyses and quantum chemical calculations of the ECD and NMR data. The stereochemistry of compound 1 was also established based on the single-crystal X-ray diffraction method. In antimicrobial assays, only (E)-4-(1H-indol-3-yl)but‑3-en-2-one (3) showed moderate activity, whereas remaining compounds were weakly active.

Stereochemistry of Dihydropyrimidinones Derivatives Synthesized by Brick Dust Catalytic Reaction

A number of catalytic synthetic reactions have been reported which play the important role in stereochemistry of compounds. The key to the success of this protocol was the generation of stereogenic centers in 1, 4-Dihydropyrimidinones (DHPMs) and the influence of catalysts on their configuration. Waste brick dust was found to be an effective catalyst, generating chiral DHPMs derivatives using aryl aldehyde, urea, and ethyl acetoacetate. This work mainly focuses on the stereochemistry of brick-dust catalyzed DHPMs derivatives. Discovery of brick dust catalyst associated with several benefits such as rapid clean reaction, simple, and ease work-up.

Amino Acid-Based Synthesis and Glycosidase Inhibition of Cyclopropane-Containing Iminosugars.

Synthesis of four iminosugars fused to a cyclopropane ring is described using l-serine as the chiral pool. The key steps are large-scale preparation of an α,β-unsaturated piperidinone followed by completely stereoselective sulfur ylide cyclopropanation. Stereochemistry of compounds has been studied by nuclear Overhauser effect spectroscopy (NOESY) experiments and 1H homonuclear decoupling to measure constant couplings. The activity of these compounds against different glycosidases has been evaluated. Although inhibition activity was low (compound 8a presents a (Ki) of 1.18 mM against β-galactosidase from Escherichia coli), interestingly, we found that compounds 8a and 8b increase the activity of neuraminidase from Vibrio cholerae up to 100%.

Synthesis of novel steroids using Mizoroki-Heck reaction, their spectroscopic analysis, anticancer activity against cervical cancer and DFT studies

Two novel steroids, 3β, 25R-spirost-5-en-3yl 3-(4-propionylphenyl)but-2-enoate(3a)and 3β, 25R-spirost-5-en-3yl 3-(4-nitrophenyl) but-2-enoate (3b) have been synthesized using a palladium catalyzed Mizoroki-Heck reaction in a two-step synthesis using diosgenin as a starting material. A new strategy was adopted involving conversion of diosgenin (compound 1) into compounds, 3β, 25R-spirost-5-en-3yl 2-chloroacetate(Compound 2), 3β, 25R-spirost-5-en-3yl trans-but-2-enoate(Compound 3) and 3β, 25R-spirost-5-en-3yl-trans-cinnamate(Compound 4) via Steglich esterification using an ionic liquid (NMP+HSO4). The synthesized compounds were then treated with 4-bromopropiophenone and 1-bromo-4-nitrobenzene using [Pd(PPh3)4] as a catalyst and K2CO3 as a base in DMF; only compound 3 underwent reaction yielding compounds (3a) and (3b). Structure elucidation of all the synthesized compounds was done by 1H NMR, 13C NMR, NOESY, IR, UV–Vis spectroscopic techniques and mass spectrometry. Stereochemistry of compound 2 was established by a single crystal X-ray structural analysis. These compounds 2, 3, 3a, 3b and 4 were investigated for cytotoxicity and apoptosis through MTT assay and Mitochondrial staining respectively, of cervical cancer cell line HeLa; the compounds showed significant anticancer activity. The molecular geometry of the compounds was optimized by density functional theory using (DFT/B3LYP) method with 6–31G (d, p) basis set and compared it with experimental data. From the low value of HOMO-LUMO energy gap, compound 3b was found to have high chemical reactivity. Nucleophilic and electrophilic sites within molecules were obtained by electrostatic potential surfaces. From global reactivity descriptors, 3b exhibited greater global electrophilicity index value (5.83eV), suggesting it to be a good electrophile. The high value of first hyperpolarizability (15.99 × 10−30 esu) for compound 3 suggested it to be ideal for non linear optical (NLO) application. From AIM (Atoms in Molecule) approach, it is found that compound 3 was more stable in comparison to other compounds.

Chemical constituents from the bark of the Cameroonian mahogany Trichilia emetica Vahl (Meliaceae)

Phytochemical investigation of the stem bark extract of Trichilia emetica led to the isolation of two new naturally occurring compounds including a prieurianin-class limonoid named trichirokin (1) and the steroid ergosta-5,24(28)-diene-3S,16S,20S-triol (4), along with nine known compounds characterized as rohituka-3 (3), rohituka-9 (2), scopoletin, benzoic acid, protocatechuic acid, lignoceric acid, β-sitosterol, stigmasterol and β-sitosterol-3-O-β-D-glucopyranoside. The crystal structures of rohituka-3 (3) and ergosta-5,24(28)-diene-3S,16S,20S-triol (4) are reported here for the first time. The structures of the compounds were elucidated by extensive spectroscopic and spectrometric data interpretation. The stereochemistry of compound 1 was established on the basis of its NOESY spectrum and the comparison of its optical rotation value with that of its congener 2. None of the reported compounds displayed antibacterial or cytotoxic activity.

Four New C9 Metabolites from the Sponge-Associated Fungus Gliomastix sp. ZSDS1-F7-2

Four new structurally related metabolites, one γ-lactone named gliomasolide F (1), one δ-lactone named gliomasolide G (2), and two medium-chain fatty acids named gliomacids A–B (3–4), each containing nine carbons in total, were identified from the sponge-associated fungus Gliomastix sp. ZSDS1-F7-2. The planar chemical structures of these novel C9 metabolites were elucidated by nuclear magnetic resonance (NMR) spectroscopic methods, in connection with the analysis of high-resolution mass spectrometry (HRMS) and infrared (IR) data. The absolute configuration of 1, was determined by comparisons of experimental circular dichroism (CD) and optical rotation (OR) value with corresponding ones computed by quantum chemistry. The relative configuration of 2 was determined by the Nuclear Overhauser effect spectroscopy (NOESY) spectrum, while its absolute configuration was tentatively determined in view of the biogenetic and biosynthetic relationships between 1 and 2. Compounds 3–4, originally as an inseparable mixture, were successfully isolated after chemical modifications. The stereo-chemistries of compounds 3–4 were assumed by comparison of 13C NMR with those of the similar moiety reported in literature, in addition to the biogenetic and biosynthetic relationships with 1. The plausible biosynthetic relationships among these four C9 metabolites were supposed. Biologically, compounds 1–4 showed no cytotoxic effect against HeLa cell line at concentrations up to 25 μg/mL, while 1 exhibited moderate antifouling activity against the settlement of Balanus amphitrite larvae with IC50 being 12.8 μg/mL and LC50 > 25 μg/mL. The co-occurrence of macrolides gliomasolides A—E and four C9 metabolites in the same fermentation culture made us assume that these C9 metabolites might be biosynthetic building blocks toward the construction of more complex macrolides such as gliomasolides A—E or other unidentified polyketides.

Computational and experimental studies of 4-thiazolidinone-cyclopropyl hybrid

Thiazolidi-4-one is a significant pharmacophore and has been known to exhibit a diverse range of biological activities for a long time. A new compound (6), thiazolidi-4-one was synthesized and characterized by spectroscopic techniques and X-ray single crystal structure. The stereochemistry of compound (6) was determined theoretically (DFT level) and experimentally (single crsytal X-ray structure) both. The DNA binding ability of the compound 6 has been assessed as using UV–Visible absorption studies and docking studies, MTT-assay study on MCF-7 cell line revealed non-toxic nature of the compound (6) in the concentration range 10–320μM.

ChemInform Abstract: Selacyclicbiflavone A, an Unusual Macrocyclic Biflavone from Selaginella uncinata (Desv.) Spring.

Abstract An unusual macrocyclic biflavone, selacyclicbiflavone A ( 1 ), have been isolated from Selaginella uncinata . The structure was elucidated on the basis of rigorous spectroscopic analysis including 1D and 2D NMR experiments as well as HRESIMS techniques. The absolute stereochemistry of compound 1 was further confirmed by comparing experimental data with calculated electronic circular dichroism (ECD) spectra. This is the first report of the macrocyclic biflavone with an unprecedented methylene bridge. A possible biosynthetic pathway was also postulated.

Three new seco-ursadiene triterpenoids from Salvia syriaca

Three new seco-ursadiene triterpenoids 1–3 together with 11 known compounds were isolated from Salvia syriaca of Jordanian origin. The compounds were identified by using NMR spectroscopy including extensive 2D NMR experiments and mass spectrometry. The structure of compound 3 was confirmed by X-ray crystallography, and the information thus obtained was used to confirm the stereochemistry of compounds 1 and 2. This is the second report of 17,22-seco-17(28),12-ursadien-22-oic acids.

Discovery anti-diabetic potent ofthiazolidinedione derivative based on virtual screening against aldose reducates

Thiazolidinedione (1) was used as a key intermediate for the synthesis of many therapeutic anti-diabetic molecule. Thus, Thiazolidinedione (1) was refluxed with aromatic aldehydes and phenol derivatives to afforded aryldine derivative (3). Moreover, the stereochemistry for compound 3 was discussed using Hartree-Fock theory geometries, and have been optimized at HF with 6-311G level of theory. The HOMO-LUMO energy gap of studied systems has been discussed. The molecular docking simulations into the active site of ALR2 were performed, and showed that, the compound 3 more suitable inhibitor against ALR2 and can used as anti- diabetic drug.

Isolation of brassicasterol, its synthetic prodrug-crystal structure, stereochemistry and theoretical studies

In the present study brassicasterol (1), was isolated from the chloroform extract of the flowers of Allamanda violacea and identified with the help of different spectroscopic techniques like 1H, 13C, 2D NMR (1H–1H COSY), IR, UV and mass spectrometry. A novel prodrug was synthesized by carrying out esterification of brassicasterol (1) with the well known drug naproxen using Steglich esterification to give 3β-(2-(6-methoxynaphthalene-2yl) propionoxy) 24 methyl cholest-5, 22-dien (2). Compounds 2 was subjected to single crystal X-ray diffraction technique and crystallized out in monoclinic form having P21 space group and stabilized by CH–π interactions. Structure and stereochemistry of compound 2 was established with the help of modern spectroscopic techniques like 1H NMR, IR, UV, mass spectrometry as well as with single crystal X-ray diffraction.Molecular geometry and vibrational frequencies of compounds 1 and 2 were calculated by density functional method (DFT/B3LYP) using 6-31G (d, p) basis set, bond parameters and IR frequencies were correlated with the experimental data. 1H and 13C chemical shifts of compound 1 and 1H chemical shifts of compound 2 were calculated with GIAO method and correlated with experimental data. Hyperconjugative interactions were studied with the help of natural bond order analysis (NBO). Electronic properties of both the compounds such as HOMO–LUMO energies were measured with the help of time dependent DFT method.

Reduction of andrographolide and its stereostructure by NMR and X-ray study

Andrographolide (1) on asymmetric reduction with nickel boride in situ led to the identification of a product as 12,13 R-dihydroandrographolide (3) in de (>96%). The structure and stereochemistry of compound 3 were established by NMR study and confirmed by X-ray crystallographic analysis. β-Substituent of γ-butyrolactone in andrographolide exerted diastereomeric selectivity in reduction. Neoandrographolide (2) under similar condition yielded 5.

Antioxidant and Antimutagenic Polyisoprenylated Benzophenones and Xanthones from Rheedia acuminata

Dichloromethane extract of the stem bark of Rheedia acuminata yielded three benzophenones with antioxidant activity, the new one named acuminophenone A (1), guttiferone K (2) and isoxanthochymol (3), along with the known xanthones formoxanthone C (4) and macluraxanthone (5). The structures were established through interpretation of their spectroscopic data, the stereochemistry of compounds (1) and (2) were resolved by experimental and computational experiments and their antioxidant activities were measured using the DPPH, ABTS and TEAC assays. The antioxidant results showed that metabolites 1, 4 and 5 had a better antioxidant activity than the reference compound quercetin. In addition, we evaluate the mutagenicity and antimutagenicity of the CH2Cl2 extract as well as of the free radical scavenger compounds 1, 4 and 5 by the AMES Salmonella/microsomal test. No mutagenicity was found in the CH2Cl2 extract using Salmonella typhimurium strains TA98, TA100, TA102, TA1537 and TA1538, with or without S9 metabolic activation. The pure compounds neither showed mutagenicity in TA 102 strain and the most important result was the strong reduction of mutagenic effect induced by hydrogen peroxide in S. typhimurium TA102, with or without S9, showed by the compounds 1 (more than 93%) and 4 (more than 88%) at 0.02 microg/plate.

Constituents of fruit pulp of Maytenus salicifolia and complete 1D/2D NMR data of 3β-hydroxy-D:B-friedo-olean-5-ene

A mixture of long-chain hydrocarbons constituted by nonacosane (29C, 7.5%), hentriacontane (31C, 48.3%), and tritriacontane (33C, 30.1%), the ester 1′-acetyloxymethylpentacosa-20′-enyl 10-hydroxydecanoate (2), β-amyrin (3), friedelin (4), and lupeol (5), and 3β-hydroxy-D:B-friedo-olean-5-ene (6) were identified as constituents of fruits of Maytenus salicifolia Reissek (Celastraceae). The structural formula and the stereochemistry of compound 6 were established by the data obtained through 1H and 13C NMR spectroscopy, including DEPT-135 and 2D (HMQC, HMBC, and NOESY) experiments. By analysis of the spectral data, it was possible to correct seven chemical shift assignments of compound 6, which were erroneous attributed and published in the scientific literature.

Lactarane sesquiterpenoids from Lactarius subvellereus and their cytotoxicity

Subvellerolactones B ( 1), D ( 2), and E ( 3), structurally unusual lactarane sesquiterpenoids, were isolated from the fruiting bodies of Lactarius subvellereus together with four known lactarane sesquiterpenes ( 4– 7). The chemical structures and stereochemistries of compounds 1– 3 were determined on the basis of spectroscopic analyses, including 1D and 2D NMR experiments and a convenient Mosher ester procedure. Subvellerolactone B ( 1) exhibited cytotoxicity against the A549, SK-MEL-2, and HCT-15 cell lines with IC 50 values of 26.5, 18.3, and 14.2 μM, respectively, and subvellerolactones D ( 2) and E ( 3) showed cytotoxicity against the A549 and HCT-15 cell lines (IC 50 ( 2): 25.1 and 17.8 μM, and IC 50 ( 3): 19.6 and 28.7 μM, respectively).

Antimicrobial and Antiparasitic Abietane Diterpenoids from the Roots of Clerodendrum eriophyllum

Chromatographic separation of the roots of a Kenyan medicinal plant, Clerodendrum eriophyllum, led to the isolation of ten abietane diterpenoids (1-10), one of which (1) was isolated for the first time from a natural source. Using spectroscopic data, the structure of 1 was determined to be 12-hydroxy-8,12-abietadiene-3,11,14-trione. Circular dichroism (CD) spectra showed that the stereochemistry of compounds 1, 3, and 6-8 belongs to the normal series of abietane diterpenes, which confirmed the absolute stereochemistry of the isolated compounds. Compounds 1-10 were evaluated for their in vitro antiplasmodial, antileishmanial, antifungal and antibacterial activities. Compounds 3 and 7 exhibited potent antifungal activity (IC50/MIC 0.58/1.25 and 0.96/2.5 microg/mL, respectively) against C. neoformans, whereas 3, 6 and 7 showed strong antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus with IC50/MIC values between 1.33-1.75/2.5-5 and 0.96-1.56/2.5 microg/mL, respectively. In addition, compounds 3 and 9 exhibited potent antileishmanial activity (IC50 0.08 and 0.20 microg/mL, respectively) against L. donovani, while 3 and 7 displayed weak antimalarial activity against Plasmodium falciparum, but 9 was inactive.

New alkaloids from Capparis spinosa: Structure and X-ray crystallographic analysis

Fruits of Capparis spinosa contain a significant amount of compounds with many health benefits. Three new alkaloids, capparisine A ( 1), capparisine B ( 2), capparisine C ( 3), and two known alkaloids, 2-(5-hydroxymethyl-2-formylpyrrol-1-yl) propionic acid lactone ( 4), and N-(3′-maleimidy1)-5-hydroxymethyl-2-pyrrole formaldehyde ( 5) were isolated from the fruits of C. spinosa L. The five compounds were purified by solvent separation, column chromatography, and preparative HPLC, consecutively. The chemical structures of compounds 1– 5 were established on the basis of a spectroscopic analysis, and the stereochemistries of compounds 1 and 2 were proved by X-ray crystallographic analysis. Nevertheless, the five compounds had no inhibitory effect on the human hepatocyte cell line HL-7702 apoptosis induced by Act D (200 ng/ml) and TNF-α (20 ng/ml) with high content screening assay.

Stereochemistry of Compounds with Coordination Number Ten

The stereochemistry of ten-coordinate rare-earth and transition-metal compounds is studied from the point of view of continuous shape measures (CShM) and derived tools. A total of 19 ideal ten-vertex polyhedra belonging to 12 different symmetry point groups have been considered, from which nine are retained for the description of the stereochemistries of all studied compounds. The structures of the coordination spheres are analyzed by families, according to the denticity and topology of the ligands. Some ligand topologies are seen to consistently favor usually neglected ideal polyhedra, such as the capped trigonal cupola.

Ulmosides A and B: Flavonoid 6-C-glycosides from Ulmuswallichiana, stimulating osteoblast differentiation assessed by alkaline phosphatase

Chemical investigation of Ulmus wallichiana stem bark resulted in isolation and identification of three new compounds (2 S,3 S)-(+)-3′,4′,5,7-tetrahydroxydihydroflavonol-6- C-β- d-glucopyranoside ( 1), (2S,3S)-(+)-4′,5,7-trihydroxydihydroflavonol-6- C-β- d-glucopyranoside ( 3) and 3- C-β- d-glucopyranoside-2,4,6-trihydroxymethylbenzoate ( 8), together with five known flavonoid-6-C-glucosides ( 2, 4– 7). Their structures were elucidated using 1D and 2D NMR spectroscopic analysis. The absolute stereochemistry in compounds 1 and 3 were established with the help of CD data analysis and comparison with the literature data analysis. All the isolated compounds ( 1– 8) were assessed for promoting the osteoblast differentiation using primary culture of rat osteoblast as an in vitro system. Compounds 1– 3 and 5 significantly increased osteoblast differentiation as assessed by alkaline phosphatase activity.