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Design, Synthesis, Inhibitory Activity, and Binding Mode Study of Novel DNA Methyltransferase 1 Inhibitors. -A series of reaction products from maleic anhydrides and tryptophan is synthesized as novel non-nucleoside DNA methyltransferase (DNMT) inhibitors. Among this series, compounds (I) are found to be more potent DNMT1 inhibitors than the previously reported substance RG 108. The binding-mode analysis of compound (Ia) is also reported. -(SUZUKI*, T.; TANAKA, R.; HAMADA, S.; NAKAGAWA, H.; MIYATA*, N.; Bioorg. Med.

We successfully prepared and crystallographically characterized the first intermolecular charge-transfer (CT)-based vapochromic compound, (EV)(HO)[Fe(CN)] (1-Wet, EV: 1,1'-diethyl-4,4'-bipyridine-1,1'-diium), an ethyl viologen-containing CT salt. 1-Wet, which is purple in color, is transformed into a brown powder (1-Dry) upon exposure to methanol vapor, drying over silica gel, or heating; 1-Dry returns to 1-Wet upon exposure to water vapor. These color changes are induced by hydration and dehydration, and gravimetric analyses suggest that 1-Dry is the dehydrated form of 1-Wet, namely, (EV)(H)[Fe(CN)]. Interestingly, desorption of water molecules from the oxonium ions in 1-Wet produces isolated protons (H) that remain in 1-Dry as counter cations. Powder X-ray crystal structure analysis of 1-Dry reveals the presence of very short contacts between the nitrogen atoms of adjacent [Fe(CN)] anions in the crystal. The isolated protons are trapped between the nitrogen atoms of cyanido ligands to form very short N···H···N hydrogen bonds. A detailed comparison of the crystal structures of 1-Wet and 1-Dry reveals that hydration and dehydration induce changes in crystal packing and intermolecular CT interactions, resulting in reversible color changes.

The methyl viologen dication, used under the name Paraquat as an agricultural reagent, is a well-known electron-acceptor species that can participate in charge-transfer (CT) interactions. The determination of the crystal structure of this species is important for accessing the CT interaction and CT-based properties. The title hydrated salt, bis(1,1'-dimethyl-4,4'-bipyridine-1,1'-diium) hexacyanidoferrate(II) octahydrate, (CHN)[Fe(CN)]·8HO or (MV)[Fe(CN)]·8HO [MV is the 1,1'-dimethyl-4,4'-bipyridine-1,1'-diium (methyl viologen) dication], crystallizes in the space group P2/c with one MV cation, half of an [Fe(CN)] anion and four water molecules in the asymmetric unit. The Fe atom of the [Fe(CN)] anion lies on an inversion centre and has an octahedral coordination sphere defined by six cyanide ligands. The MV cation is located on a general position and adopts a noncoplanar structure, with a dihedral angle of 40.32 (7)° between the planes of the pyridine rings. In the crystal, layers of electron-donor [Fe(CN)] anions and layers of electron-acceptor MV cations are formed and are stacked in an alternating manner parallel to the direction of the -2a + c axis, resulting in an alternate layered structure.

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