N-H···O and C-H···F hydrogen bonds in the incommensurately modulated crystal structure of adamantan-1-ammonium 4-fluorobenzoate.

At low temperatures the organic salt adamantan-1-ammonium 4-fluorobenzoate, C10H18N(+)·C7H4FO2(-), possesses an incommensurately modulated crystal structure. The effect of the modulation on the atomic arrangement and intermolecular interactions is studied by analysing single-crystal X-ray diffraction data within the (3 + 1)-dimensional superspace approach and superspace group P2(1)/n(α0γ)00. The modulation strongly affects the position of the atoms as well as their atomic displacement parameters. Nevertheless, the molecular cations and anions are built by rigid moieties, which vary their orientation with respect to each other as a function of the phase of the modulation t. Cations and anions are connected into slabs by dense N-H···O and C-H···F hydrogen-bonded networks, which are characterized by being rather rigid and which show only a little variation as a function of the phase of the modulation t.

Antiviral agents derived from novel 1-adamantyl singlet nitrenes.

BACKGROUND: Amantadine constitutes an interesting, diamond crystal lattice-shaped, antivirally active amine with an inhibitory effect on influenza A viruses causing common 'flu' in humans. Unfortunately, amantadine forfeited most of its therapeutic potential because of resistance development in recent influenza A virus isolates. The antiviral efficacy of amantadine congeners can be chemically modified, resulting in re-constitution, improvement and/or extension of antiviral activities mediated by amino-adamantyls. METHODS: Newly synthesized compounds were evaluated towards HIV type-1 (HIV-1) replication in primary human lymphocytes. One N-phenacyl amantadine derivative was investigated for inhibiting the in vitro replication of respiratory viruses (influenza A viruses, influenza B virus, human parainfluenza virus type 3 and severe acute respiratory syndrome coronavirus). RESULTS: Two ketone-stabilized 1-adamantyl singlet nitrenes were discovered serendipitously. To our best knowledge these are the first persistently stable nitrenes to be reported. Their structure was proved by determining the X-ray single crystal structure of one hydrolytic elaboration product. This salt adduct revealed an incommensurately modulated crystal structure, which was solved by extensive computational refinement. We could show that ketone-stabilized 1-adamantyl singlet nitrenes are versatile synthons for the synthesis of antiviral drug candidates. An amantadine-folate conjugate was inhibitory on HIV-1 replication in primary human lymphocytes, and one N-phenacyl amantadine derivative was inhibitory towards low pathogenic avian influenza A virus (H5N1) replication in vitro. CONCLUSIONS: These results indicate that the aromatic-aliphatic ketone-stabilized 1-adamantyl singlet nitrenes, beyond being of fundamental interest in organic chemistry, represent versatile synthons for the synthesis of new amantadine-related potentially antiviral drugs.

Cyclobutane derivatives as novel nonpeptidic small molecule agonists of glucagon-like peptide-1 receptor.

A novel cyclobutane class of nonpeptidic glucagon-like peptide-1 (GLP-1) receptor agonists, exemplified by 3, was identified using receptor binding and multiple response element/cAMP response element (MRE/CRE)-driven reporter gene assays. The structures of 3 and its three isomers were elucidated by NMR, HRESIMS, and X-ray crystallography. A series of structural modifications were also made based on the core structure of 3 with different substitution groups at the west and east ends. Among these analogues, compound 16 was found to be 4- to 5-fold more potent than 3 both in vitro and in vivo.

Constituents of Trigonostemon chinensis.

Phytochemical investigation on the stem bark and wood of Trigonostemon chinensis led to the isolation of four new dinorditerpenoids, trigonostemons A-D (1, 3, 5, 6), a new phenanthrenone, trigonostemon E (7), and a new bisindole alkaloid, trigonostemon F (8). The structures were established by extensive spectroscopic methods. The absolute configurations of 1-6 were determined by X-ray crystallography, circular dichroism, quantum chemical TDDFT calculations, and chemical transformations. The relative configuration of 8 was confirmed by X-ray diffraction analysis.

Insecticidal heterolignans--tubuline polymerization inhibitors with activity against chewing pests.

Starting from natural product podophyllotoxin 1 substituted heterolignans were identified with promising insecticidal in vivo activity. The impact of substitution in each segment of the core structure was investigated in a detailed SAR study, and variation of substituents in both aromatic moieties afforded derivatives 5 and 43 with broad insecticidal activity against lepidopteran and coleopteran species. In vitro measurements supported by modeling studies indicate that heterolignans 3-134 act as tubuline polymerization inhibitors interacting with the colchicine-binding site. Insect specific structure-activity effects were observed showing that the insecticidal SAR described herein differs from reported cytotoxicity studies.

The study of different solid forms of Emodepside.

Emodepside is an endoparasiticide used in veterinary drugs. It exists in four different crystal forms which were characterised using DSC, TGA, evolved gas analysis (using FT-IR spectroscopy), hot-stage microscopy, FT-Raman, FT-IR and FT-NIR spectroscopy and powder X-ray diffraction. Thermal analysis showed that the forms II-IV contain considerable amounts of water being easily lost upon heating. Hot-stage microscopy indicated that the crystal structures do not change upon the loss of water. To examine whether the forms II-IV are hydrates or modifications of Emodepside having water adsorbed to the crystal surface and/or absorbed into disordered defect regions, the behaviour of the forms at different relative humidities was analysed using FT-Raman and FT-NIR spectroscopy and vapour sorption analysis. Changes in the C=O stretching region in the Raman spectra upon the removal of water revealed that all three forms represent non-stoichiometric hydrates forming isomorphic dehydrates. Sorption analysis indicated the presence of localised water molecules in the structure of form IV. Several OH combination bands of water were found in the NIR spectrum of each form indicating differently bound water molecules. Crystal structure analysis of form IV at ambient humidity revealed four well-defined water positions in the asymmetric unit.

Antidiabetic activities of triterpenoids isolated from bitter melon associated with activation of the AMPK pathway.

Four cucurbitane glycosides, momordicosides Q, R, S, and T, and stereochemistry-established karaviloside XI, were isolated from the vegetable bitter melon (Momordica charantia). These compounds and their aglycones exhibited a number of biologic effects beneficial to diabetes and obesity. In both L6 myotubes and 3T3-L1 adipocytes, they stimulated GLUT4 translocation to the cell membrane--an essential step for inducible glucose entry into cells. This was associated with increased activity of AMP-activated protein kinase (AMPK), a key pathway mediating glucose uptake and fatty acid oxidation. Furthermore, momordicoside(s) enhanced fatty acid oxidation and glucose disposal during glucose tolerance tests in both insulin-sensitive and insulin-resistant mice. These findings indicate that cucurbitane triterpenoids, the characteristic constituents of M. charantia, may provide leads as a class of therapeutics for diabetes and obesity.

Diterpenoids from the pericarp of Platycladus orientalis.

Eight labdane-type diterpenes, 7beta,13S-dihydroxylabda-8(17),14-dien-19-oic acid (1), 12R,15-dihydroxylabda-8(17),13E-dien-19-oic acid (3c), 12R,15-dihydroxylabda-8(17),13Z-dien-19-oic acid (3d), 12R,13R,14S-trihydroxylabda-12,15-epoxy-8(17)-en-19-oic acid (4a), 12S,13S,14R-trihydroxylabda-12,15-epoxy-8(17)-en-19-oic acid (4b), 15-hydroxy-12-oxolabda-8(17),13E-dien-19-oic acid (5), 14R,15-dihydroxylabda-8(17),12Z-dien-19-oic acid (7a) and 14S,15-dihydroxylabda-8(17),12Z-dien-19-oic acid (7b), along with 20 known diterpenoids, were isolated from the pericarp of Platycladus orientalis. Their structures were unambiguously elucidated by NMR spectroscopic and single crystal X-ray diffraction analyses, as well as via chemical correlation conversion. NMR spectroscopic data of known isomers 8c and 8d were reported as a supplement to existing data.

Mono- and Di-sesquiterpenoids from Chloranthus spicatus.

Three new dimeric sesquiterpenoids, chloramultilides B-D ( 1- 3), along with 10 known sesquiterpenoids, were isolated from the whole plant of Chloranthus spicatus. Their structures were established by physical data (1D and 2D NMR, MS). The structure and absolute configuration of 1 was confirmed by X-ray crystallography. Compound 1 exhibited moderate in vitro antifungal activity.

Synthesis and anthelmintic activity of substituted (R)-phenyllactic acid containing cyclohexadepsipeptides.

The substituted (R)-phenyllactic acid containing cyclohexadepsipeptides (CHDPs) represent novel enniatin derivatives with strong in vivo activities against the parasitic nematode Haemonchus contortus Rudolphi in sheep. 2D NMR spectroscopic analysis revealed for the substituted (R)-phenyllactic acid containing CHDPs one major conformer with an unsymmetrically folded conformation lacking a cis-amide bond. A correlation between the substitution pattern and its anthelmintic activity was found. Here we report on a simple total synthetic pathway of the precursor for this particular type of CHDPs and an efficient modification of the benzylic side chain (R-PhLac(2)).

The Melting Point Alternation in the Short-Chain n-Alkanes: Single-Crystal X-Ray Analyses of Propane at 30 K and of n-Butane to n-Nonane at 90 K.

A less dense packing is observed in the odd-numbered n-alkanes compared to the even-numbered members, which consequently lowers melting temperatures. The reason for this is that the even-numbered n-alkanes have optimal intermolecular interactions at both ends (see the picture on the left), while the odd-numbered ones possess these only at one end-at the other end the intermolecular distances are longer (right).