Glycosylation of panaxadiol

Glycosylation of 3β,12β-dihydroxy-20R,25-epoxydammarane (panaxadiol) (1) under Koenigs–Knorr, Helferich, and ortho-ester reaction conditions was studied. Condensation of panaxadiol and 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosylbromide (2) in the presence of silver oxide and 4-Å molecular sieves in dichloroethane gave a mixture of acetylated panaxadiol 3- and 12-O-β-D-glucopyranosides (3:1 ratio). Reaction of diol 1 and D-glucose tert-butylorthoacetate (3) in the presence of 2,4,6-collidinium perchlorate in chlorobenzene resulted in regioselective formation of panaxadiol 12-O-β-D-glucopyranoside tetraacetate. Reaction of equimolar amounts of 1 and glycosyl donor 2 in the presence of Hg(II) cyanide in nitromethane at 90°C was accompanied by opening of the tetrahydropyran ring and gave 3β,12β,25-trihydroxydammar20(22)E-ene 12-O-β-D-glucopyranoside tetraacetate. Panaxadiol 3- and 12-O-β-D-glucopyranosides and 3β,12β,25-trihydroxydammar-20(22)E-ene 12-O-β-D-glucopyranoside tetraacetate were synthesized for the first time.     

Structure of methyl-7-methoxy-7-phenyl-6-<Emphasis Type="Italic">endo</Emphasis>-halobicyclo[3.1.1]heptane-6-<Emphasis Type="Italic">exo</Emphasis>-carboxylate diastereomers in single crystals

The structure of diastereomeric methyl-7-anti-methoxy-7-syn-phenyl-and methyl-7-syn-methoxy-7-anti-phenyl-6-endo-bromobicyclo[3.1.1]heptane-6-exo-carboxylates 2a and 3a and their chlorine-and iodine-substituted analogs 2b and 3c was studied by XRD. The diastereomers differ in the geometrical parameters of the carbon framework of the molecules. The C(1)-C(2)-C(3)-C(4)-C(5)-C(6) six-membered ring is in the intermediate conformation between envelope and chair in structures 2 and envelope in structures 3. In compound 2a, the cyclobutane fragment has a higher degree of folding than in 3a; one of the possible reasons for that is the donor-acceptor interaction between the 6-methoxycarboxylic and 7-methoxy groups in molecule 2a.     

Concise synthesis of two natural steroidal glycosides isolated from <Emphasis Type="Italic">Allium schoenoprasum</Emphasis>

Two natural steroidal glycosides, diosgenin 3-O-α-l-rhamnopyranosyl-(1→2)-[β-d-glucopyranosyl-(1→4)]-β-d-glucopyranoside (1) and laxogenin 3-O-α-l-rhamnopyranosyl-(1→2)-[β-d-glucopyranosyl-(1→4)]-β-d-glucopyranoside (2) with important cytotoxic activity against the HCT 116 and HT-29 human colon cancer cell lines have been efficiently synthesized via straightforward sequential glycosylation reaction with the combined use of N-phenyltrifluoroacetimidates and trichloroacetimidates donors at room temperature. All structures of the synthesized new compounds were identified by ¹H NMR, ¹³C NMR and HRMS spectra.     

Molecular dynamic studies of amyloid-beta interactions with curcumin and Cu<Superscript>2+</Superscript> ions

Amyloid-beta (Aβ) peptide readily forms aggregates that are associated with Alzheimer’s disease. Transition metals play a key role in this process. Recently, it has been shown that curcumin (CUA), a polyphenolic phytochemical, inhibits the aggregation of Aβ peptide. However, interactions of Aβ peptide with metal ions or CUA are not entirely clear. In this work, molecular dynamics (MD) simulations were carried out to clear the nature of interactions between the 42-residue Aβ peptide (Aβ-42) and Cu²⁺ ions and CUA. Altogether nine different models were investigated, and more than 2 µs of the simulation data were analyzed. The models represent the possible modes of arrangement between Aβ-42 and Cu²⁺ ions and CUA, respectively, and were used to shed light on the Aβ-42 conformational behavior in the presence of Cu²⁺ ions and CUA molecules. Obtained data clearly showed that the presence of a CUA molecule or a higher concentration of copper ions significantly affect the conformational behavior of Aβ-42. Calculations showed that the change of the His13 protonation state (Aβ(H13δ)-Cu²⁺, Aβ(H13δ)-Cu²⁺ -CUA models) leads to higher occurrence of the Asp23-Lys28 salt bridge. Analyzes of trajectories revealed that C-terminal β-sheet structures occurred significantly less frequently, and CUA promoted the stabilization of the α-helical structure. Further, calculations of the Aβ-42 complex with CUA and Cu²⁺ ions showed that CUA can chelate the Cu²⁺ ion and directly interact with Aβ, which may explain why CUA acts as an inhibitor of Aβ aggregation.     

Cycloaminomethylation of dihydric phenols catalyzed by <Emphasis Type="Italic">d</Emphasis>- and <Emphasis Type="Italic">f</Emphasis>-metal compounds

An efficient method has been developed for the synthesis of 7,16,25-triaryl-7,8,16,17,25,26-hexahydro-6H,15H,24H-tribenzo[f,m,t][1,5,8,12,15,19,3,10,17]hexaoxatriazacyclohenicosines, 3,8-diaryl-2,3,4,7,8,9-hexahydrobenzo[1,2-e:4,3-e′]bis[1,3]oxazines, 3,9-bis(chlorophenyl)-3,4,9,10-tetrahydro-2H,8H-benzo[1,2-e:3,4-e′]bis[1,3]oxazines, and 2,9-bis(chlorophenyl)-1,2,3,8,9,10-hexahydrobenzo[1,2-e:6,5-e′]bis-[1,3]oxazines via cycloaminomethylation of pyrocatechol, resorcinol, and hydroquinone with N,N-bis(methoxymethyl) anilines in the presence of samarium catalysts.     

New derivatives of 4-quinaldinol

The reactions of 1, 1, 3-trichloro-1-propene and also 1, 1, 1-trichloro-2-propene with acetoacetic ester gave α-(γ, γ-dichlorallyl)acetoacetic ester (I). In the reactions with aniline and o- and p-toluidines, the corresponding α-(γ, γ-dichloroallyl)-β-arylamino-crotonic esters were produced, thermal cyclization of which gave 2-methyl-3-(γ, γ-dichloroallyl)-4-hydroxyquinoline (II) and its 6CH₃- (III) and 8CH₃- (IV) homologs. With phosphorus oxychloride, II–IV gave the corresponding 4-chloro-substituted quinolines (V–VII); with concentrated sulfuric acid, II–VII were converted into the corresponding β-quinolinylpropionic acids VIII–XIII.     

Crystal and molecular structures of two modifications of a chelate compound of Pb[(<Emphasis Type="Italic">iso</Emphasis>-C<Subscript>4</Subscript>H<Subscript>9</Subscript>)<Subscript>2</Subscript>PS<Subscript>2</Subscript>]<Subscript>2</Subscript>

A chelate compound Pb[(iso-C₄H₉)₂PS₂]² is synthesized. Using X-ray diffraction data, the crystal structures of two modifications of this compound are determined (X8 APEX diffractometer, MoK _α radiation, 14169 F _hkl , R = 0.0480 for the low temperature α-form and 6261 F _hkl , R = 0.0387 for the β-form studied at ambient temperature). The crystals are triclinic: a = 11.047(2) Å, b = 14.486(3) Å, c = 32.048(6) Å; α = 91.30(3)°, β = 99.73(3)°, γ = 101.61(3)°, V = 4942.9(17) ų, Z = 8, ρ_calc = 1.682 g/cm³ (α-modification) and a = 11.2124(5) Å, b = 14.6989(7) Å, c = 17.1644(6) Å; α = 109.393(1)°, β = 94.989(2)°, γ = 101.649(1)°, V = 2576.83(19) ų, Z = 4, ρ_calc = 1.613 g/cm³ (β-modification), space group \(P\bar 1\) for both polymorphs. The structures are molecular, coordination cores of PbS₄ are tetragonal pyramids with Pb atoms in the vertices and S atoms in the base. In both structures intermolecular Pb...S contacts yield supramolecular ensembles comprising by four molecules, where PbS₄₊₂ cores form planar aggregates of edge-sharing octahedra. The ensembles are joined by weak intermolecular S...S interactions resulting in the development of polymeric chains along the a axis.     

Electronic and crystal structure of (N-CH<Subscript>3</Subscript>-2,2′-bipyridinium)(dodecahydro-dicarba-<Emphasis Type="Italic">nido</Emphasis>-undecaborate)

The compound [N-Me-2,2′-Bipy]⁺[C₂B₉H₁₂]^?-(N-CH₃-2,2′-bipyridinium)(dodecahydro-dicarba-nidoundecaborate) has been synthesized, and its structure has been determined. The compound was defined by IR, ¹¹B and ¹⁴N NMR, and X-ray photoelectron spectroscopy. Crystal data: C₁₃H₂₃B₉N₂, M = 304.62, monoclinic crystals, space group P2₁/c, a = 11.840(4) Å, b = 10.051(3) Å, c = 15.573(6) Å, β = 102.43(3)°, V = 1809.8(10) ų, Z = 4, d _calc = 1.118 g/cm³, R = 0.0607.     

Composition of essential oils of four <Emphasis Type="Italic">Hedychium</Emphasis>species from Vietnam

Background

Vietnam is a country blessed with many medicinal plants widely used as food and for medicinal purposes, and they contain a host of active substances that contribute to health. However, the analysis of chemical constituents of these plant species has not been subject of literature discussion.

Results

In this study, the chemical compositions of essential oils of four Hedychium species, obtained by hydrodistillation, were determined by means of gas chromatography-flame ionization detector (GC-FID) and gas chromatography–mass spectrometry (GC-MS) techniques. Individually, α-pinene (52.5%) and β-pinene (31.8%) were present in the leaf oil of Hedychium stenopetalum Lodd., while linalool (45.2%), (E)-nerolidol (8.7%) and α-pinene (5.0%) were identified in the root. The leaf of Hedychium coronarium J. König was characterized by α-pinene (20.0%), linalool (15.8%), 1,8-cineole (10.7%), α-pinene (10.1%) and α-terpineol (8.6%); while α-pinene (23.6%), α-humulene (17.1%) and β-caryophyllene (13.0%) were identified in the root. Hedychium flavum Roxb., gave oil whose major compounds were α-pinene (22.5%), α-humulene (15.7%) and β-caryophyllene (10.4%) in the leaf; α-humulene (18.9%), β-caryophyllene (11.8%) and α-pinene (11.2%) in the stem, as well as α-pinene (21.8%), linalool (17.5%) and 1,8-cineole (13.5%) in the root. The main constituents of Hedychium ellipticum Buch.-Ham. ex Smith were (E)-nerolidol (15.9%), α-pinene (11.8%) and bornyl acetate (9.2%) in the leaf with 1,8-cineole (40.8%), α-pinene (18.3%) and α-pinene (11.0%) occurring in the root.

Conclusions

Ubiquitous monoterpenes and sesquiterpenes were identified as characteristic markers for Hedychium species. This work is of great importance for the evaluation of Hedychium essential oils grown in Vietnam.

     

Crystal structure of KPb<Subscript>2</Subscript>Cl<Subscript>5</Subscript> and KPb<Subscript>2</Subscript>Br<Subscript>5</Subscript>

The KPb₂Cl₅ and KPb₂Br₅ crystals are monoclinic (P2₁/c) with a microtwinned structure. X-ray analysis of chloride resulted in the parameters a = 8.854(2) Å, b = 7.927(2) Å, c = 12.485(3) Å; β = 90.05(3)°, d_calc = 4.78(1) g/cm³ (STOE STADI4, MoK_α, 2θ_max = 80°), R₁ = 0.0702 for 4094 F ≥ 4 σ(F) reflections. For bromide, a = 9.256(2) Å, b = 8.365(2) Å, c = 13.025(3) Å; β = 90.00(3)°, d_calc = 5.62(1) g/cm³ (Bruker P4, MoK_α, 2θ_max = 70°), R₁ = 0.0692 for 3076 F ≥ 4 (F) reflections.     

Synthesis,crystal structure,and thermal analysis of a copper(II) complex with imidazo[4,5-<Emphasis Type="Italic">f</Emphasis>]1,10-phenantroline

A new complex, [Cu₂(μ ₂-Cl)₂(IP)₂Cl₂] · 4H₂O (IP = imidazo[4,5-f]1,10-phenathroline), was synthesised and characterised by elemental analysis, thermal analysis, IR spectra, and X-ray crystallography. The results showed that the complex crystallises in the monoclinic space group P \(\bar 1\); a = 7.880 (2) Å, b = 9.227(2) Å, c = 10.694(2) Å; α = 97.788(4)°, β = 100.637(4)°, γ = 95.841(3)°; V = 750.7(3) ų, and Z = 1. The complex is further stabilised by H-bonds and a π-π stacking interaction between the pyridine and benzene rings of two neighbouring molecules with the centroid.centroid distance of 3.498(3) Å, leading to a 3D supramolecular architecture. Thermal decomposition procedure of the complex explored by TG-DTG has three stages, and the final product is Cu in residual rate of 16.18 % (calculated to be 16.26 %).     

Condensation of aldehydes and ketones

The alkaline condensation of β-aceto-and β-propionaphthalenes with furfural has given, respectively, 2-(α-furfuryl)-1, 3-di(β-naphthoyl)-propane and 3-(α-furyl)-2,4-di(β-naphthoyl)pentane; both δ-diketones have also been obtained by the Michael condensation. Under more severe conditions, two molecules of furfural condense with three molecules of β-acetonaphthalene to form 2, 4-di(α-furyl)-1, 3, 5-tri(β-naphthoyl)pentane. Under similar conditions, benzaldehyde exhibits only a feeble capacity for triketone condensation with β-acetonaphthalene. The condensation of β-propionaphthalene with furfural has given the new compound furylidenepropionaphthalene. It has been shown that both under the conditions of the improved Chichibabin pyridine synthesis and under the conditions of the Leuckhardt reaction, 3-(α-furyl)-1, 3-di(β-naphthoyl)propane gives 4-(α-furyl)-2, 6-di(β-naphthyl)pyridine.     

3-(1-Methyl-1-nitroethyl-1-<Emphasis Type="Italic">ONN</Emphasis>-azoxy)-4-aminofuroxan. Synthesis and transformations of the amino group

A four-step procedure to convert 4-(1-methyl-1-nitroethyl-1-ONN-azoxy)-3-cyanofuroxan into 3-(1-methyl-1-nitroethyl-1-ONN-azoxy)-4-aminofuroxan was developed. The pathways of transformation of the amino group of the synthesized compound into N-nitramino-, N-alkyl-N-nitramino-, N,N’-methylenediamino-, N,N’-methylene-N,N’-dinitramino-, and azo groups were studied.     

Crystal and molecular structure of <Emphasis Type="Italic">tris</Emphasis>(<Emphasis Type="Italic">m</Emphasis>-chlorophenyl)phosphine selenide

The crystal and molecular structure of tris(m-chlorophenyl)phosphine selenide, C₁₈H₁₂Cl₃PSe (I), was investigated by X-ray diffraction (XRD) analysis. The trigonal rhombohedral structure of I (space group \(R\overline 3 c\), a = 14.110(2) Å, c = 32.360(4) Å, Z = 12) was solved by direct methods and refined by least squares in an anisotropic approximation (R = 0.029) for 1319 averaged measured reflections (CAD-4 automatic diffractometer, λCuK_α).     

Bioactive compounds from <Emphasis Type="Italic">Smilax excelsa</Emphasis> L.

Phytochemical investigation of EtOAc extract of Smilax excelsa has led to isolation and structure elucidation of five compounds. The structures of these compounds are established by different spectroscopic techniques including 1D and 2D-NMR, HRMS and ECD spectroscopy. The compounds were: solanesol (1), violasterol A (2), trans-resveratrol (3), 5-O-caffeoylshikimic acid (4) and 6-O-caffeoyl-β-d-fructofuranosyl-(2-1)-α-d-glucopyranoside (5). The configuration of compound 2 was established by electronic circular dichroism (ECD) spectroscopy. Meanwhile the cytotoxicity and antibacterial activity of the compounds were evaluated by MTT and MIC assays. Compounds 1 and 2 showed promising inhibition on MCF-7 cell line with IC₅₀ of 161.6 and 190.0 µM, respectively. Also compounds 2 and 3 illustrated activity against Staphylococcus aureus with MIC values of 142.5 and 136.9 µM, respectively.     

Synthetic transformations of isoquinoline alkaloids. Synthesis of 1-halo derivatives of <Emphasis Type="Italic">endo</Emphasis>-ethenotetrahydrothebaine and their behavior in the heck reaction

Bromination of endo-ethenotetrahydrothebaine derivatives having a pyrrolidine ring fused at the C⁷-C⁸ bond, namely 1′-substituted 4,5α-epoxy-6α,14-etheno-3,6-dimethoxy-17-methyl-2′,5′,7β,8β-tetrahydro-1′H-14α-pyrrolo[3′,4′:7,8]morphinan-2′,5′-diones, 1′-aryl-4,5α-epoxy-6α,14-etheno-3,6-dimethoxy-17-methyl-2′,5′,7β,8β-tetrahydro-1′H-14α-pyrrolo[3′,4′:7,8]morphinans, and 4,5α-epoxy-6α,14-etheno-2′α-hydroxy-3,6-dimethoxy-17-methyl-1′-phenyl-2′,5′,7β,8β-tetrahydro-1′H-14α-pyrrolo[3′,4′:7,8]morpphinan-5′-one, with molecular bromine in formic acid smoothly afforded the corresponding 1-bromo derivatives. Iodination of 4,5α-epoxy-6α,14-etheno-3,6-dimethoxy-17-methyl-1′-phenyl-2′,5′,7β,8β-tetrahydro-1′H-14α-pyrrolo[3′,4′:7,8]-4,5α-epoxy-6α,14-etheno-3,6-dimethoxy-17-methyl-1′-phenyl-2′,5′,7β,8β-tetrahydro-1′H-14α-pyrrolo[3′,4′:7,8]-morphinan-2′,5′-dione with iodine(I) chloride gave 4,5α-epoxy-6α,14-etheno-1-iodo-3,6-dimethoxy-17-methyl-1′-phenyl-2′,5′,7β,8β-tetrahydro-1′H-14α-pyrrolo[3′,4′:7,8]morphinan-2′,5′-dione. The resulting 1-halo derivatives were brought into the Heck reaction with acrylic acid esters to obtain 1-[(E)-2-(alkoxycarbonyl)ethenyl]-substituted compounds. Demethylation of the 6-methoxy group in 1-bromo-endo-ethenotetrahydrothebaines was accomplished using boron(III) bromide in chloroform.     

Analogs of ecdysteroids with a tetrasubstituted Δ<Superscript>8,14</Superscript>-bond

By hydrogenation of (20R,22R)-6α,14α,25-trihydroxy-and (20R,22R)-6β,14α,25-trihydroxy-2,3:20,22-bis(isopropylidenedioxy)-5α-cholest-7-enes on a catalyst (Raney nickel) the corresponding (5α,6α)-and (5β,6β)-epimers of previously unknown Δ^8,14-6-hydroxy derivatives of ecdysteroids were synthesized.     

New nitrogen-containing<Emphasis Type="Italic">α</Emphasis>-oxides

N-(2,3-Epoxypropyl)-α-pyrrolidone and N-(2,3-epoxypropyl)-α-suecinimide have been obtained for the first time. It has been shown that N-(2,3-epoxypropyl)-α-pyrrolidone readily reacts with ammonia and diethylamine to form the corresponding amino alcohols.     

Structural studies of nickel(II) complexes with 1-<Emphasis Type="Italic">tert</Emphasis>-butylimidazole-2-thione and 3-phenyl-5-methyl-pyrazole ligands

The nickel(II) complexes dichlorobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂Cl₂] (1), dinitratobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂(NO₃)₂] (2), dichloro-bis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)Cl₂] (3) and dinitratobis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)(NO₃)₂] (4) have been synthesized and studied. The single crystal X-ray diffraction analysis was carried out for 1 and 4 {Bruker Kappa Apex-II CCD diffractometer, MoK _α radiation}. Crystal data for 1: monoclinic C2/c, a = 16.949(2) Å, b = 8.6647(10) Å, c = 15.461(3) Å, β = 117.662(4)°, V = 2011.1(5) ų, Z = 4, D _calc = 1.460 g/cm³. Crystal data for 4: triclinic P-1, a = 9.9775(7) Å, b = 11.2254(8) Å, c = 14.8068(10) Å, α = 75.401(4)°, β = 87.422(4)°, γ = 74.874(4)°, V = 1548.86(19) ų, Z = 2, D _calc = 1.405 g/cm³. Coordination core of complex 1 adopts distorted tetrahedral geometry whereas core 4 has distorted octahedral geometry. The bonded nitrates are of two types coordinating as monodentate and bidentate ligands.     

Experimental and Theoretical Vibrational Spectra of Sideridiol Isolated from <Emphasis Type="Italic">Sideritis</Emphasis> Species

Sideridiol (ent-7α,18β-dihydroxykaur-15-ene) one of the ent-kaurene diterpenoid, is isolated from the genus Sideritis L. belongs to the family of Lamiaceae. The vibrational frequencies of sideridiol in the ground state have been calculated using the Density Functional Theory (DFT) method with the 6-31G(d) and 6 31+G(d,p) basis sets. The calculated vibrational frequencies have been compared with that of obtained experimental IR spectrum.