Stereochemistry Of Compounds Research Articles

Stereochemistry of 16a-Hydroxyfriedelin and 3-Oxo-16-methylfriedel-16-ene Established by 2D NMR Spectroscopy

Friedelin (1), 3β-friedelinol (2), 28-hydroxyfriedelin (3), 16α-hydroxyfriedelin (4), 30-hydroxyfriedelin (5) and 16α,28-dihydroxyfriedelin (6) were isolated through fractionation of the hexane extract obtained from branches of Salacia elliptica. After a week in CDCl3 solution, 16α-hydroxyfriedelin (4) reacted turning into 3-oxo-16-methylfriedel-16-ene (7). This is the first report of a dehydration followed by a Nametkin rearrangement of a pentacyclic triterpene in CDCl3 solution occurring in the NMR tube. These seven pentacyclic triterpenes was identified through NMR spectroscopy and the stereochemistry of compound 4 and 7 was established by 2D NMR (NOESY) spectroscopy and mass spectrometry (GC-MS). It is also the first time that all the 13C-NMR and 2D NMR spectral data are reported for compounds 4 and 7.

Cyclic diarylheptanoids from Myrica nana inhibiting nitric oxide release

Investigation of the roots of Myrica nana afforded five new cyclic diarylheptanoids, myricananins A–E ( 1–5), two new artifacts of myricananins A and B ( 6– 7), and four known compounds, 12-hydroxymyricanone ( 8), alnusonol ( 9), myricatomentogenin ( 10), and actinidione ( 11). The structures of these new compounds were established by detailed spectroscopic methods. The stereochemistry of compounds 1 and 2 were determined by single-crystal X-ray diffraction. In exception of compounds 2, 6 and 10, all the other compounds were examined for their inhibitory effects on nitric oxide production in lipopolysaccharides-activated macrophages. Compounds 1, 3, 7, 8 and 9 inhibited the release of nitric oxide with IC 50 values of 45.32, 63.51, 52.81, 30.19 and 46.18 μM, respectively. Furthermore, compound 1 was found to inhibit the expression of inducible nitric oxide synthase.

Two New Alkylated Piperidine Alkaloids from Western Honey Mesquite: Prosopis glandulosa Torr. var. torreyana

Prosopis glandulosa Torr. var. torreyana (L. Benson) M. C. Johnston root bark, collected in Texas, yielded two new alkylated piperidine alkaloids, namely 3-isocassine (1) and N-methyl-3-isocassine (2), together with the previously reported N-methylcassine (3). In addition, the alkylated piperidinyl indolizidine alkaloid juliprosopine (4) was isolated from the leaves of the same plant. The structures and stereochemistry of compounds 1–4 were determined from 1D and 2D NMR data, including COSY, HMQC, HMBC and NOESY experiments, and ESI-HRMS. Juliprosopine (4) demonstrated antimicrobial activities against a panel of microorganisms, including potent antifungal activities against Aspergillus fumigatus.

Cytotoxic Polyketides from the Marine Sponge Discodermia calyx

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A novel flavonoid from Lespedeza virgata (Thunb.) DC.: Structural elucidation and antioxidative activity

Bioactivity guided fractionation of the ethanolic extract of the whole plants of Lespedeza virgata (Thunb.) DC. resulted in the isolation of a novel flavonoid ( 1) along with five known compounds 2– 6. The molecular and structural formula as well as the stereochemistry of compound 1 were determined using data obtained from 1H and 13C NMR spectra, DEPT135 and by 2D HSQC, HMBC, 1H– 1H correlated spectroscopy ( 1H– 1H COSY), and nuclear overhauser effect spectroscopy (NOESY) experiments. The superoxide anion scavenging activities of all isolated compounds were evaluated by the hypoxanthine nitro blue tetrazolium and ESR methods and the new compound 1 showed the strongest antioxidative activity 95.79% (IC 50 = 0.14 mg/ml).

Penicidones A–C, three cytotoxic alkaloidal metabolites of an endophytic Penicillium sp.

Along with the known secondary metabolites lumichrome, physcion, and emodin-1,6-dimethyl ether, three alkaloids named penicidones A–C ( 1–3) were isolated from the culture of Penicillium sp. IFB-E022, an endophytic fungal strain residing in the stem of Quercus variabilis (Fagaceae). The structures of penicidones A–C were established by a correlative interpretation of spectroscopic data including IR, UV and HR-ESI-MS, as well as by analysis of a set of 1D and 2D NMR experiments. The stereochemistry of compounds 1 and 2 was obtained by comparison of the optical rotation with those of vermistatin and its analogues. Penicidones A–C were the first group of natural products possessing a penicidone framework. Compounds 1–3 exhibited moderate cytotoxicity against four cancer cell lines.

Cytotoxic Polyketides from the Marine Sponge Discodermia calyx

Bioassay-guided fractionation of the MeOH extract from the sponge Discodermia calyx collected off the coast of Jeju Island, South Korea, led to the isolation of a polyketide, icadamide C (1), along with previously reported theopederin K (3). Structure elucidation was performed by a combination of high resolution mass and 2D-NMR (principally COSY, HMBC, HSQC, and NOESY) spectroscopy. Stereochemistry of compound 1 was determined as 2R*, 3R*, 6R*, 10S*, 11S*, 12R*, 13S*, 15R* and 2'S by NMR data and Marfey analysis. Isolated metabolites displayed potent cytotoxic activity against a small panel of five human solid tumor cell lines with ED50 values of less than 0.1 μg/mL.

Labdane diterpenes from the seeds of Platycladus orientalis

Two new labdane diterpenes, 14(R),15-dihydroxy-8(17),12(E)-labdadien-19-oic acid (1) and 16-methyl–12,15-epoxy-8(17),13-labdadien-19-oic acid (2), together with four known compounds, were isolated from the seeds of Platycladus orientalis. Their structures were established by spectroscopic methods. The stereochemistry of compound 1 was defined by X-ray crystallographic analysis.

Secondary metabolites from Opuntia ficus-indica var. saboten

A butanol fraction, from the methanolic extract of Opuntia ficus-indica var. saboten, on purification either by preparative TLC or reversed phase HPLC, yielded three chemical components: isorhamnetin 3- O-(6″- O- E-feruloyl)neohesperidoside ( 1), (6 R)-9,10-dihydroxy-4,7-megastigmadien-3-one-9- O-β- d-glucopyranoside ( 2) and (6 S)-9,10-dihydroxy-4,7-megastigmadien-3-one-9- O-β- d-glucopyranoside ( 3) along with 15 known compounds. Structures of compounds ( 1– 3) were elucidated by aid of spectroscopic analyses. The absolute stereochemistry in compounds 2 and 3 was established with the help of CD data analysis and comparison with the literature data. In a DPPH radical scavenging assay, compound 1 showed moderate inhibitory activity (IC 50 = 45.58 μg/ml).

Synthesis of C2-β-Fluoro-Substituted Adenine Nucleosides Via Pivaloyl Derivatives of Adenosine and 3 -Deoxyadenosine

Syntheses of 9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)adenine (9) its 3-deoxy derivative, 9-(2,3- dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (16), with the DAST treatment of the corresponding 3,5- di-O-pivaloyladenosine (7) and its 3-deoxy derivative 14 are described. The role of the pentofuranose ring stereochemistry of nucleosides 7 and 14 in the DAST fluorination is discussed. Stereochemistry of compounds 7 and 14 as well as fluorides 9 and 16 was studied by the PSEUROT 6.3 program. Keywords: Nucleosides, purine, 2'-deoxyfluoro derivatives, PSEUROT analysis

Ring-B Linked Bidihydroflavonoids fromThuidium kanedae Sak

A new bidihydroflavonoid, thuidinin 1, together with 5 known compounds including one known biflavonoid 3′,3′′′-binaringenin (2) and four other known natural products pentadecane (3), methyl β-orcinolarboxylate (4), β-sitosterol (5) and daucostenol (6), were isolated from leaves of Thuidium kanedae Sak. Their structures were established on the basis of 1D and 2D spectroscopic analysis. The absolute stereochemistry of compounds 1 and 2 was determined by CD spectra.

Andropanolide and Isoandrographolide, Minor Diterpenoids from Andrographis paniculata: Structure and X-ray Crystallographic Analysis

Phytochemical investigation of the leaves of Andrographis paniculata has led to the isolation of a new labdane type diterpenoid, andropanolide (1), along with seven known diterpenoids including isoandrographolide (2), previously reported as a rearrangement product of andrographolide. The structures and stereochemistry of compounds 1 and 2 were established by X-ray crystallographic analysis.

Three Dammarane-Type Saponins fromGynostemma pentaphyllum

Three new dammarane-type saponins, compounds 1 - 3, were isolated from the aerial parts of Gynostemma pentaphyllum. Their structures were determined using NMR analysis and acid hydrolysis. The structure and stereochemistry of compound 1 were confirmed by X-ray crystallography.

Triterpene Saponins from the Leaves of Ilex kudingcha

Nine new triterpene saponins, ilekudinosides K-S (1-9), and eight known triterpene saponins were isolated from the 70% ethanol extract of the leaves of Ilex kudingcha. The new saponins were characterized as 3-O-alpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl-alpha-kudinlactone (1), 3-O-beta-D-glucopyranosyl(1-->3)-alpha-L-arabinopyranosyl-beta-kudinlactone (2), 3-O-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranosyl-gamma-kudinlactone (3), 3-O-beta-D-glucopyranosyl(1-->2)-beta-D-glucopyranosyl-alpha-kudinlactone (4), 3-O-beta-D-glucopyranosyl(1-->2)-alpha-L-arabinopyranosyl-alpha-kudinlactone (5), 3-O-beta-D-glucopyranosyl(1-->3)-alpha-L-arabinopyranosyl-alpha-kudinlactone (6), 3-O-alpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl-beta-kudinlactone (7), 3-O-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranosyl-beta-kudinlactone (8), and 3-O-alpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl-gamma-kudinlactone (9), respectively. The structures and stereochemistry of compounds 1-9 were elucidated by spectroscopic data interpretation and chemical degradation.

A new germacranolide from Carpesium cernuum

As a part of our interest in biologically active germacranolides from the genusCarpesium (Compositae), we have investigated the constituents ofCarpesium cernuum. This paper reports the isolation and structural elucidation of a new germacranolide, cernolide A (Compound 1), from the herb. The structure of Compound 1 was determined as 2α,3β-dihydroxy-9-angeloxygermacra-4-en-6,12-olide on the basis of spectral evidence. The skeleton of Compound 1 was elucidation by IR, MS,1H and13CNMR, COSY, HMQC and HMBC experiments. The stereochemistry of Compound 1 was deduced by ROESY spectral data. Finally, the procedures of extraction and isolation were described in detail.

QSAR Modeling of Datasets with Enantioselective Compounds using Chirality Sensitive Molecular Descriptors*

Shape descriptors used in 3D QSAR studies naturally take into account chirality; however, for flexible and structurally diverse molecules such studies require extensive conformational searching and alignment. QSAR modeling studies of two datasets of fragrance compounds with complex stereochemistry using simple alignment-free chirality sensitive descriptors developed in our laboratories are presented. In the first investigation, 44 α-campholenic derivatives with sandalwood odor were represented as derivatives of several common structural templates with substituents numbered according to their relative spatial positions in the molecules. Both molecular and substituent descriptors were used as independent variables in MLR calculations, and the best model was characterized by the training set q 2 of 0.79 and external test set r 2 of 0.95. In the second study, several types of chirality descriptors were employed in combinatorial QSAR modeling of 98 ambergris fragrance compounds. Among 28 possible combinations of seven types of descriptors and four statistical modeling techniques, k nearest neighbor classification with CoMFA descriptors was initially found to generate the best models with the internal and external accuracies of 76 and 89%, respectively. The same dataset was then studied using novel atom pair chirality descriptors (cAP). The cAP are based on a modified definition of the atomic chirality, in which the seniority of the substituents is defined by their relative partial charge values: higher values correspond to higher seniorities. The resulting models were found to have higher predictive power than those developed with CoMFA descriptors; the best model was characterized by the internal and external accuracies of 82 and 94%, respectively. The success of modeling studies using simple alignment free chirality descriptors discussed in this paper suggests that they should be applied broadly to QSAR studies of many datasets when compound stereochemistry plays an important role in defining their activity.

Cycloartane-type triterpenoids from Sphaerophysa salsula

Four novel cycloartanes, named sphaerophysone A (1), B (2), C (3) and D (4), were isolated from the ethanol extract of Sphaerophysa salsula (Pall.) DC. The structures were elucidated on the basis of spectral evidence, and the stereochemistry of compound 1 was defined by X-ray crystallographic analysis. Sphaerophysone B (2) may be an artifact formed in the isolation procedure.

Chemistry at the apical position of square-pyramidal copper(II) complexes: synthesis, crystal structures, and magnetic properties of mononuclear Cu(II), and heteronuclear Cu(II)–Hg(II) and Cu(II)–Co(II) complexes containing [Cu(AA)(BB)] + moieties (AA=acetylacetonate, salicylaldehydate; BB=1,10-phenanthroline, Me 2bipy=4,4 ′-dimethyl-2,2 ′-bipyridine)

New families of mononuclear and heteropolynuclear complexes have been obtained by using [Cu(AA)(BB)] + building-blocks (AA=acetylacetonate or salicylaldehydate; BB=1,10-phenanthroline, 4,4 ′-dimethyl-2,2 ′-bipyridine). The following mononuclear complexes have been structurally characterized: [Cu(acac)(Me 2bipy)]ClO 4 ( 1), [Cu(acac)(Me 2bipy)(NCS)] ( 2), [Cu(acac)(phen)(NCS)] ( 3). In compound 1 the copper(II) exhibits a square planar geometry, while the stereochemistry of compounds 2 and 3 is square pyramidal, with the isothiocyanato ligand coordinated in the apical position. The reaction between 2 and HgCl 2 affords a trinuclear complex, [{Cu(acac)(Me 2bipy)(μ-NCS)} 2Hg(SCN) 2] ( 4). The reaction between 3 and HgCl 2 leads to tetranuclear Cu 2Hg 2 compound, [{Cu(acac)(phen)(NCS)} 2{(ClHg) 2(NCS) 2}] ( 5), with a unique structure, and to a trinuclear complex, [{Cu(acac)(phen)(NCS)} 2Hg(SCN) 2] ( 6). The structure of 5 consists of a {Hg 2(NCS) 2} ring on which two [Cu(acac)(phen)(NCS)] moieties are attached. In compounds 4, 5 and 6 the mercury atoms are tetracoordinated. By reacting [Cu(sal)(phen)(OClO 3)] with (NEt 4) 2[Co(NCS) 4], a heterohexanuclear compound is obtained: [{Cu(sal)(phen)(SCN)} 2Co(NCS) 2] 2 ( 7), with the following topology of the metallic centers: Cu–Co–Cu–Cu–Co–Cu. The cobalt(II) ions in 7 are tetracoordinated by nitrogen atoms arising from two bridging and two terminal thiocyanato ligands. The central copper(II) ions are bridged by the phenoxo oxygen atom arising from the sal − ligand. The cryomagnetic properties of compounds 2– 5 and 7 have been investigated and discussed. The magnetic behavior of compounds 2– 5 has been ascribed to intermolecular exchange interactions mediated by the stacking interactions. The magnetic interaction between Cu(II) and Co(II) in 7 was found ferromagnetic ( J=+0.6 cm −1), as theoretically predicted. The exchange interactions between the central copper(II) ions is antiferromagnetic ( J=−5.8 cm −1).

Reactions of [C,N,N′]-cyclometallated platinum compounds with phosphines: transphobia and effect of the chloro substituents : Crystal structure of [PtCl(3,5-C 6H 2Cl 2CHNCH 2CH 2NMe 2)(PPh 3) 2

The reaction of [C,N,N′]-cyclometallated platinum compounds [PtX(C 6H 4− n Cl n CHNCH 2CH 2NMe 2)] ( 1a– 1g) with triphenylphosphine gave either [C,N]-cyclometallated compounds [PtX(C 6H 4− n Cl n CHNCH 2CH 2NMe 2)PPh 3] ( 2), in which PPh 3 is trans to the imine nitrogen, or compounds [PtX(C 6H 4− n Cl n CHNCH 2CH 2NMe 2)(PPh 3) 2] ( 4), with cleavage of the metallacycle. The stereochemistry of compounds 2 is the expected one according to the transphobia effect, while formation of compounds 4 takes place only when there is a chlorine atom adjacent to the metallated carbon. An ionic compound 3 has also been obtained using the chelate diphosphine 1,2-bis(diphenylphosphino)ethane. All compounds have been fully characterised including a structure determination for [PtCl(3,5-C 6H 2Cl 2CHNCH 2CH 2NMe 2)(PPh 3) 2] ( 4f).

Sesquiterpene lactones from Anthemis altissima and their anti-Helicobacter pylori activity.

Seven sesquiterpene lactones, (-) sivasinolide (1), a new naturally occurring eudesmanolide (altissin, 2), desacetyl-beta-cyclopyrethrosin (3), tatridin-A (4), 1-epi-tatridin B (5), 1alpha,10beta-epoxy-6-hydroxy-1,10H-inunolide (6), and spiciformin (7), were isolated from Anthemis altissima. Also isolated were 10 known flavonoids, namely, apigenin (8), kaempferol 4'-methyl ether (9), quercetin (10), quercetin 3-methyl ether (11), isorhamnetin (12), rhamnetin (13), 6-hydroxyquercetin 3,6,4'-trimethyl ether (14), isoquercetrin (15), taxifolin (16), and eriodictyol (17), and one phenolic acid, chlorogenic acid (18). The structure and the stereochemistry of compound 2 were deduced by spectroscopic methods. The in vitro activity of the sesquiterpene lactones (1-5) against Helicobacter pylori, as well as against three Gram-positive and three Gram-negative bacteria growing aerobically, was tested using the microdilution method. Compounds 8-18 have also been tested against H. pylori.