Three new triterpene glycosides, intercedensides A (1), B (2), and C (3), were isolated from the sea cucumber Mensamria intercedens Lampert, which is found in the South China Sea, and their structures have been elucidated by spectroscopic analysis (NMR and ESIMS) and chemical transformations. Intercedensides A (1) and C (3) have a conjugated double bond (22E,24-diene) in the side chain of the aglycon. Intercedenside B (2) has two beta-D-xylose and two sulfate groups in the carbohydrate chain. All three glycosides showed significant cytotoxicity against 10 human tumor cell lines with ED(50) in the range 0.6-4.0 microg/mL. Intercedenside A (1) exhibited significant in vivo antineoplastic activity against mouse Lewis lung cancer and mouse S180 sarcoma. On the basis of these initially promising results, intercedensides A-C merit further study as potential anticancer agents.

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Taking advantage of the steric hindrance and charge-driving effects, four air-stable pentagonal bipyramidal mononuclear Dy compounds were hydrothermally synthesized. With a tetradentate ligand, N,N'-bis(2-methylenepyridinyl)ethylenediamine (Bpen), invariably coordinates to Dy in an equatorial plan, 1-3 achieve an orderly transformation of the ligand field by sequentially replacing the remaining sites of the Dy ion. Compound 4 possesses the same coordination atoms but a different peripheral coordination sphere with 3. Magnetic characterizations display that the compounds are field-induced single-ion magnets (SIM) with actually low barriers, even though 2 has both the same atoms and a similar geometry of the first sphere compared with [Dy(bbpen)Cl] (2', H bbpen=N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl)ethylenediamin), a high-performance SIM previously reported. Detailed ab initio calculations have been employed to further elucidate the electronic and magnetic structure of the low-lying energy levels of compounds 1-4 and 2'. The theoretical results indicate there is an apparent difference in the electronic structure for these compounds. The analysis on the electrostatic potential further demonstrates that although the pentagonal bipyramidal D is one of the ideal configurations expected, the electron density of the donor atoms from the different hybridizations and other functional groups, outside the first sphere, should also be considered in the rational design of promising molecular magnets.

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