POLAND Marmesinine-C20H24O9, coumarin β-D-glucoside derivative-appears in several plants-e.g. Ruta graveolens, playing role of biocontrolling, antipathogenic compound. Marmesinine was first isolated by Reisch in 1970. Its molecular structure was assigned using NMR spectroscopy by Duddeck and coworkers (1993). In spite of development in separation techniques-marmesinine is difficult to crystallize, appearing as 'amorphous powder' (Kitayama, 2001). The crystal structure of marmesinine was determined from single microcrystal diffraction and, independently, from powder diffraction-with the aim of comparing the conformations and precision of both structural models. The single crystal experiment (CAD-4 diffractometer, copper radiation), yielded lattice parameters a = 7.8503, b = 5.9850, c = 40.579 Å, α = β = γ = 90°, in P212121 space group. The structure was solved and refined to R = 0.035, and could serve as good reference for powder methods. The powder diffraction experiments (Grochowski, Serda, Baehtz, Knapp, 2001), were done on the B2 beamline of DESY-HASYLAB (Hamburg) using wavelength 1.3572 Å and a channel-cut type analyzer crystal. The pattern was indexed with TREOR90 giving lattice parameters a = 7.8449(3), b = 5.9903(2), c = 40.598(2) Å, α = β = γ = 90° with figure of merit M20=158, F20=506. The effective resolution of the data (d = 1.75 Å) was limited by the sample, hence structure solution was attempted by global optimization rather than direct methods. Structure solution was carried out by simulated annealing, using the program DASH ver. 2.0. Several simulated annealing runs were tried to achieve the global minimum. (C. a.) belong to the oldest natural therapeutics, known and used in Europe since 1630. They are also very interesting both from the chemical (stereospecific reactions) and crystallographic (intermolecular interactions) points of view. First X-ray crystal data for some C. a., were determined in 1959 [1], while the absolute configuration of quinidine was reported in 967 [2]. Recently we found in CSDS about 90 crystal structures of C. a. and their derivatives. The most important problems solved in result of the X-ray structure analysis concerned: i) conformations observed in crystals versus energetically preferred conformations of isolated molecules, ii) conformational behavior of different diastereoisomers, iii) effect of protonation and esterification on conformation and other parameters of molecular geometry, iv) interactions of C. a. molecules with the crystalline environment via hydrogen bonds and π-π stacking. Essential for understanding the structure-biological activity relationships are the studies of inactive threo epimers of C. a. and of metal-C. a. interactions. Among still unsolved questions the most urgent seem to be the mode of C. a. interactions with biological macromolecules and relatively low stereospecificity of their active diastereoisomers towards various biological targets. Quinolones are common antibacterial agents consisting N1-substituted 4-oxo-1,4-dihydroquinoline with an...
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