Structural analysis of an impurity of the drug landiolol.

In a course of development and preparation of landiolol (1a), a known ultra-short-acting ß-blocker, process quality control by HPLC and LC-MS analysis consistently showed an impurity peak ranging from 0.05% to 0.15 % and exhibiting a molecular mass m/z 887. To identify the hitherto unknown impurity, we prepared one of the possible landiolol derivatives with the same molecular mass for proper spectral characterization (NMR and MS). Its equivalence with the unknown impurity was then confirmed by LC-MS analysis. Ultimately, using fragmentation patterns in LC-MS and selective two-dimensional NMR experiments, the structure of the impurity was assigned as [(4S)-2,2-dimethyl-1,3-dioxolan-4-yl]methyl 3-{4-[(2S)-2-hydroxy-3-(3-{4-[(2S)-2-hydroxy-3-[(2-{[(morpholin-4-yl)carbonyl]amino}ethyl)amino]propoxy]phenyl}-N-(2-{[(morpholin-4-yl)carbonyl]amino}ethyl)propanamido)propoxy]phenyl}propanoate (2). It was found that the impurity was present in two rotameric forms at room temperature. The synthesis and NMR characterization of (2) are discussed.

NXO building blocks for backbone modification of peptides and preparation of pseudopeptides.

The design and synthesis of novel building blocks for peptide modification, termed "NXO", is reported. We describe the utility of these building blocks to prepare new pseudo- and oligopeptides and demonstrate the efficient assembly of modified tripeptides using both conventional liquid phase peptide synthesis and solid supported synthesis. Pertaining to the study of NXO in peptide mimicry, the structure of NXO-incorporating tripeptide beta-strand mimics was investigated in the N(L)AlaO incorporating beta-sheet model compound 13. Evidenced by spectroscopy and computation, 13 selectively adopts a beta-structure in chloroform and characteristically samples the NXO-modified backbone site in the core beta-sheet region. ROESY (HNMR) and molecular dynamics data suggest that when disrupting the cross-strand hydrogen-bonding pattern by switching the solvent from CDCl(3) to d(3)-MeOH, the main conformation with peptide and NXO-peptide backbones similar to that in root mean square deviation of corresponding backbone atoms (rmsd) is preserved.

Red light as a 12-oxo-leukotriene B4 antagonist: an explanation for the efficacy of intensive red light in the therapy of peripheral inflammatory diseases.

To explain the successful treatment of various inflammatory diseases by using intensive red light, a non-linear theory is presented for the interaction of electric dipoles with light involving frequency doubling. It is applied to analyze the influence of light on organic molecules with permanent electric dipoles. The molecule 5-hydroxy-12-oxo-(5S,6Z,8E,10E,14Z)-6,8,10,14-eicosatetraenoic acid, 12-oxo-leukotriene B4 (12-Oxo-LTB4, an intermediate in the lipoxygenase-catalyzed path of arachidonic acid metabolism), is suspected to play a major role in the healing process, as, first, it plays a key role in the metabolism of leukotriene B4 (LTB4), which in many diseases acts as a source of inflammatory reactions; second, its dipole resonance is located at a wavelength of 316 nm, which can be excited by a 632 nm source through frequency doubling. From the structure of 12-Oxo-LTB4 and the knowledge of the partial charges of its 54 atoms, the equivalent values for dipole charges and dipole moment are derived. The power balance demonstrates that intensive red light with a power density of 0.4 W/cm2 transfers sufficient energy to 12-Oxo-LTB4 to render it biologically inactive. Hence, by generating a reactive high-energy leukotriene pathway intermediate, the law of mass action steers the chemical equilibrium to interrupt the inflammatory cascade.