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Isotopes in Environmental and Health... Sep 2006The complex formed between 4-methylpyridine and pentachlorophenol (4MPPCP) crystallises in a triclinic space group. If the same complex is synthesized from deuterated...
The complex formed between 4-methylpyridine and pentachlorophenol (4MPPCP) crystallises in a triclinic space group. If the same complex is synthesized from deuterated pentachlorophenol, it crystallizes in an entirely different monoclinic polymorph. Using solid-state NMR of samples synthesized with a full range of deuteration levels, crystallized from solution or the melt, and in the presence or absence of seeds, we have confirmed that the isotopomers indeed have different thermodynamically stable crystal structures. The roots of this phenomenon of isotopomeric polymorphism apparently lie in the differences in hydrogen bonding between the polymorphs. The triclinic form has a relatively short hydrogen bond. High-field solid-state NMR shows both the 1H chemical shift and the 2H electric quadrupole coupling of the hydrogen involved in the bond to be strongly temperature-dependent, indicating a low-lying excited state of the hydrogen bond longitudinal vibration. Inelastic neutron scattering of isotopomers of 4MPPCP has allowed us to identify the three orthogonal vibrational modes of the hydrogen in the hydrogen bond, at 29.7, 145, and 205 meV (240, 1168, and 1651 cm(-1)). The longitudinal mode is the lowest in energy, and it indicates a slightly asymmetric low-barrier double-well potential. Intrinsic to such potentials is a very small difference in zero-point energies (ZPEs) between the protonated and deuterated forms. As a contrast, the monoclinic form has a comparatively normal hydrogen bond, in which the proton and deuteron ZPEs should be different by approximately 500 cm(-1). A scenario can be envisaged where the triclinic protonated form is lower in energy than the monoclinic protonated form, but the triclinic deuterated form is higher in energy than the monoclinic deuterated form. This evidently accounts for the difference in relative stabilities of the two forms upon isotope substitution.
Topics: Crystallization; Magnetic Resonance Spectroscopy; Pentachlorophenol; Picolines
PubMed: 16870562
DOI: 10.1080/10256010600840093 -
ChemMedChem Jun 2014The lipophilicity of ten photoactivatable platinum(IV) diazido prodrugs of formula trans,trans,trans-[Pt(N3 )2 (OH)2 (R)(R')] (where R and R' are NH3 , methylamine,...
The lipophilicity of ten photoactivatable platinum(IV) diazido prodrugs of formula trans,trans,trans-[Pt(N3 )2 (OH)2 (R)(R')] (where R and R' are NH3 , methylamine, ethylamine, pyridine, 2-picoline, 3-picoline or thiazole) has been determined by their retention times on reversed-phase HPLC. The lipophilicity of the complexes shows a linear dependence on the lipophilicity (partition coefficient) of the ligands. Accumulation of platinum in A2780 human ovarian cancer cells after one hour drug exposure in the dark is compared with their cytotoxic potency on activation with UVA (365 nm) and to their lipophilicity. No correlation between lipophilicity and intracellular accumulation of platinum was observed, perhaps suggesting involvement of active transport and favoured influx of selected structures. Furthermore, no correlation between platinum accumulation and photocytotoxicity was observed in A2780 cancer cells, implying that the type of intracellular damage induced by these complexes plays a key role in their cytotoxic effects.
Topics: Amines; Antineoplastic Agents; Cell Line, Tumor; Cell Survival; Chromatography, High Pressure Liquid; Cisplatin; Coordination Complexes; Humans; Isomerism; Picolines; Platinum; Thiazoles; Ultraviolet Rays
PubMed: 24840112
DOI: 10.1002/cmdc.201402066 -
Molecules (Basel, Switzerland) Aug 2022Amphichoterpenoids D () and E (), two new picoline-derived meroterpenoids with a rare 6/6/6 tricyclic pyrano[3,2-c]pyridinyl--pyranone scaffold, were isolated from the...
Amphichoterpenoids D () and E (), two new picoline-derived meroterpenoids with a rare 6/6/6 tricyclic pyrano[3,2-c]pyridinyl--pyranone scaffold, were isolated from the ascidian-derived fungus SYSU-MS7908. Their structures, including the absolute configurations, were established by extensive spectroscopic methods (1D and 2D NMR and high-resolution mass spectrometry) and ECD calculations. Compounds and showed anti-acetylcholinesterase (anti-AChE) activities with IC values of 12.5 μM and 11.6 μM, respectively. The binding interactions between , , and AChE were investigated using molecular docking analyses.
Topics: Animals; Beauveria; Magnetic Resonance Spectroscopy; Molecular Docking Simulation; Molecular Structure; Picolines; Terpenes; Urochordata
PubMed: 36014315
DOI: 10.3390/molecules27165076 -
BMJ (Clinical Research Ed.) Oct 1989
Topics: Cathartics; Child; Child, Preschool; Citrates; Colonoscopy; Fiber Optic Technology; Humans; Inflammatory Bowel Diseases; Organometallic Compounds; Picolines
PubMed: 2511982
DOI: 10.1136/bmj.299.6707.1101-c -
Journal of Bacteriology Aug 1958
Topics: Bacillus megaterium; Picolines; Picolinic Acids
PubMed: 13563413
DOI: 10.1128/jb.76.2.167-178.1958 -
Archiv Der Pharmazie Und Berichte Der... Oct 1963
Topics: Chemistry, Pharmaceutical; Glycosides; Hexoses; Pentoses; Picolines; Pyridines; Research
PubMed: 14205490
DOI: 10.1002/ardp.19632961010 -
Organic Letters Feb 2020A general method has been developed for the formation of glycosyl chlorides and bromides from picolinic esters under mild and neutral conditions. Benchtop stable...
A general method has been developed for the formation of glycosyl chlorides and bromides from picolinic esters under mild and neutral conditions. Benchtop stable picolinic esters are activated by a copper(II) halide species to afford the corresponding products in high yields with a traceless leaving group. Rare β glycosyl chlorides are accessible via this route through neighboring group participation. Additionally, glycosyl chlorides with labile protecting groups previously not easily accessible can be prepared.
Topics: Bromides; Chelating Agents; Chlorides; Esters; Glycosides; Molecular Structure; Picolines
PubMed: 32026682
DOI: 10.1021/acs.orglett.0c00078 -
The Journal of Biological Chemistry Mar 1969
Topics: Cold Temperature; Fluorescence; Hydrogen-Ion Concentration; Luminescent Measurements; Methanol; Picolines; Pyridoxal Phosphate; Spectrum Analysis
PubMed: 5773051
DOI: No ID Found -
Drug and Therapeutics Bulletin Dec 1976
Clinical Trial
Topics: Aged; Cathartics; Clinical Trials as Topic; Humans; Picolines
PubMed: 795627
DOI: No ID Found -
Stomatologiia 2008
Review
Topics: Antioxidants; Humans; Periodontal Diseases; Picolines
PubMed: 19209390
DOI: No ID Found