We report on the synthesis and self-assembly study of novel supramolecular monomers encompassing quadruple hydrogen-bonding motifs and metal coordinating 2,2'-bipyridine units. When mixed with metal ions such as Fe 2+ or Zn 2+ , the tetrahedron cage complexes are formed in quantitative yields and full diastereoselectivity, even in highly polar acetonitrile or methanol solvents. The symmetry of the complexes obtained has been shown to depend critically on the flexibility of the ligand. Restriction of the rotation of the hydrogen-bonding unit with respect to the metal coordinating site results in a T-symmetric cage, whereas by introducing flexibility either through a methylene linker or rotating benzene ring allows the formation of S 4-symmetric cages with selffilled interior. In addition, the possibility to select between tetrahedral cages or helicates, and to control the dimensions of the aggregate, has been demonstrated with three component assembly using external hydrogen-bonding molecular inserts or by varying the radius of the metal ion (Hg 2+ vs Fe 2+). Self-sorting studies of individual Fe 2+ complexes of with ligands of different sizes revealed their inertness toward ligand scrambling.

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A facile and scaleable synthetic process of compound 2, an important intermediate for synthesis of ketolide semisynthetic antibiotics, was developed starting from commercially available clathromycin with an overall yield of ∼74%. This synthetic pathway was composed of four steps from compound 3 which could be prepared from clathromycin without using expensive reagents such as EDC‚HCl (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride) or more active reagents such as methanesulfonic anhydride. This new process was efficient and practical as demonstrated by scale-up to prepare more than 1 kg of pure compound 2.

The genus Berchemia (Rhamnaceae) with more than 31 species occurred in Asia. About eighteen species are distributed in south part of China. Their roots have been used as a remedy for gall stones, stomach-ache, rheumatism and lumbago in Chinese folk medicine. 1) Hitherto, B. racemosa, B. pakistanica, B. zeyheri, B. formosana, B. polyphylla, and B. floribunda were chemically investigated and some lignans, 2) flavones, 3-9) aromatic glycosides 10,11) and quinines [12][13][14] were isolated. In the course of our search for active components from the genus Berchemia, ethanol extracts of the roots of B. floribunda showed obviously hepatoprotective effects against D-galactosamine-induced toxicity. Furthermore, from bioactivity-directed fractionation four novel anthraquinone-benzisochromanquinone dimers, named floribundiquinones A-D (1-4) were isolated, along with six known anthraquinones, 10-(chrysophanol-7Ј-yl)-10-hydroxy-chrysophanol-9-anthrane (5), 15) physcion (6), 16) chrysophanol (7), 1,5,8-trihydroxy-3-methyl-anthraquinone (8), 17) aloe-emodin (9), 18) and xanthorin (10). 17) Their structures including the absolute axial stereochemistry were elucidated on the basis of spectroscopic methods. Hepatoprotective activities of compounds 1-4, 6, and 7 were evaluated against D-galactosamine-induced toxicity in WB-F344.Floribundiquinone A (1) was obtained as a brown amorphous powder. The IR spectrum indicated the presence of hydroxyl, hydrogen bonded carbonyl and aromatic groups. The high resolution (HR)-EI-MS of 1 showed a molecular ion peak at m/z 570.1513 corresponding to molecular formula C 32 H 26 O 10 . The UV spectrum of 1 showed absorption maxima at 203, 222, 254, 283, and 434 nm in MeOH. These data suggested that 1 has quinone groups.The 1 H-NMR spectrum of 1 ( Four novel anthraquinone-benzisochromanquinone dimers, named floribundiquinones A, B, C, and D (1-4), along with six known anthraquinones, 10-(chrysophanol-7-yl)-10-hydroxychrysophanol-9-anthrane (5), physcion (6), chrysophanol (7), 1,5,8-trihydroxy-3-methyl-anthraquinone (8), aloe-emodin (9), and xanthorin (10), were isolated from the roots of Berchemia floribunda. Their structures including the absolute axial stereochemistry were elucidated on the basis of spectroscopic methods. Floribundiquinones represent a novel carbon skeleton with an anthraquinone-benzisochromanquinone unit. Hepatoprotective activities were evaluated against D-galactosamine-induced toxicity in WB-F344 rat hepatic epithelial stem-like cells.