Simple dinitro substituted calix[4]arene forming a honeycomb-like architecture with hydrophobic channels

A rather easily structured permethylated dinitro calix[4]arene was found to exhibit large, stable and rigid channels in the solid state. These were obtained as guest free as well as solvent filled species and proved to reversibly adsorb selected organic solvents. Combined use of QMB measurements and X-ray powder diffraction revealed the predominantly reversible interaction of dichloromethane vapour with the channel structure as well as the integrity of the nanopores during adsorption and desorption. Examination of the flexible host component by NMR spectroscopy revealed a mixture of interchanging conformational isomers which could explain the high sensitivity of the crystallization process from the employed solvents

<span style="font-size:10.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-US">Flavones and triterpenes from the leaves of <i style="mso-bidi-font-style: normal">Vitex peduncularis</i></span>

279-282A new flavone, 4'-acetoxy-5-hydroxy-6,7-dimethoxyflavone 1 together with four known compounds, cirsimaritin <b style="mso-bidi-font-weight: normal">2, genkwanin 3, 3α-friedelinol <b style="mso-bidi-font-weight: normal">4 and 3β-friedelinol 5 have been isolated from the leaves of Vitex peduncularis Wall. (Verbenaceae). The structure of the new flavone was elucidated by detailed spectral (including 2D-NMR) and chemical studies. </span

Conformational behaviour and first crystal structures of a calix[4]arene featuring a laterally positioned carboxylic acid function in unsolvated and solvent-complexed forms

A detailed conformational analysis of a rarely investigated type of compound, a laterally monosubstituted calix[4]arene (1, which has a carboxylic acid function in the lateral position), is reported. 2D solution NMR techniques at various temperatures and in different solvents have been used, showing interesting aggregation behaviour for the different conformers. The first illustrations of crystal structures of this compound type are given, including the unsolvated carboxylic calix[4]arene and two mixed solvent complexes containing EtOH–H2O and EtOH–THF, respectively. Isostructurality calculations have been carried out, allowing detailed comparison of the investigated structures, and an unusual conformational chirality isomerism of the calixarene molecule is demonstrated

First total synthesis of the biscarbazole alkaloid oxydimurrayafoline

We report the first total synthesis of oxydimurrayafoline via nucleophilic substitution at the benzylic position at C-3 of the carbazole framework.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

Red Algae (Rhodophyta) from the Coast of Madagascar: Preliminary Bioactivity Studies and Isolation of Natural Products

Several species of red algae (Rhodophyta) from the coastal regions of Madagascar have been investigated for their natural products. The most abundant compound was cholesterol (5) in combination with a series of oxidized congeners. The brominated indoles 1–3 along with the sesquiterpene debilone (4) have been isolated from Laurencia complanata. For the first time, debilone (4) has been obtained from a marine plant. From the methanol extract of Calloseris sp., we have achieved the second isolation of the unusual A-ring contracted steroids (−)-2-ethoxycarbonyl-2β-hydroxy-A-nor-cholest-5-en-4-one (9) and phorbasterone B (10). The crude extracts of Laurencia complanata exhibited antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Streptococcus pneumoniae, and Candida albicans

The first example of a one-step synthesis of 2'-O-acetyl aryl-D-glucopyranosides

A selective acidic system for partial deacetylation of phenolic d-glucopyranosides per-acetates has been developed that allows synthesis of the corresponding 2′-O-acetyl-d-glucosides. Many disadvantages of generally used methods for preparing such mono-acyl derivatives involving multistep procedures or the use of enzymes are avoided. The ion at m/z 289 in mass spectra of their TMS derivatives indicates a particular and characteristic fragmentation pattern of these 2′-O-acetyl derivatives of d-glucopyranosides. Quantum-chemical calculations applying B3LYP/TZVP level of theory revealed the stability of 2′-O-acetyl glucopyranoside if compare with 3′-, 4′- and 6′- O-acetyl glucopyanosides

The first example of a one-step synthesis of 2'-O-acetyl aryl-D-glucopyranosides

A selective acidic system for partial deacetylation of phenolic d-glucopyranosides per-acetates has been developed that allows synthesis of the corresponding 2′-O-acetyl-d-glucosides. Many disadvantages of generally used methods for preparing such mono-acyl derivatives involving multistep procedures or the use of enzymes are avoided. The ion at m/z 289 in mass spectra of their TMS derivatives indicates a particular and characteristic fragmentation pattern of these 2′-O-acetyl derivatives of d-glucopyranosides. Quantum-chemical calculations applying B3LYP/TZVP level of theory revealed the stability of 2′-O-acetyl glucopyranoside if compare with 3′-, 4′- and 6′- O-acetyl glucopyanosides

Influence of laterally attached alkyl groups on the conformational behaviour of a basic calix[4]arene: combined NMR, molecular mechanics and X-ray study

Three new calixarenes 3–5 featuring an alkyl residue of different chain lengths attached to one of the central ring methylene groups of the basic calix[4]arene 1 have been prepared. A systematic study that includes also the lower homologous compound 2 showing the effect of the alkyl substitution on the conformational behaviour of the calixarene framework in comparison with the unsubstituted parent compound 1 is reported. The application of special 2D NMR techniques, 2D-EXSY and ROESY methods at various temperatures establishes that calixarenes 2–5 adopt the partial cone conformation of lower symmetry and far less the symmetric cone and 1,2-alternate conformations. In solution, they undergo a fast interconversion with relatively low activation energies of about 15 kcal/mol at room temperature. The conformer distribution is well reproduced by molecular mechanistic calculations (MMFF94), indicating the present conformers to assume the lowest steric energies. A single-crystal X-ray structure of the lateral ethyl derivative 2 corroborates these results, showing the molecule in a sterically favourable partial cone conformation