@article {668, title = {Latonduines A and B, new alkaloids isolated from the marine sponge Stylissa carteri: Structure elucidation, synthesis, and biogenetic implications}, journal = {Organic Letters}, volume = {5}, number = {15}, year = {2003}, note = {ISI Document Delivery No.: 703AJTimes Cited: 17Cited Reference Count: 18}, month = {Jul}, pages = {2735-2738}, type = {Article}, abstract = {Latonduines A (6) and B (7), two new alkaloids with unprecedented heterocyclic skeletons, have been isolated from the Indonesian marine sponge Stylissa carted. The structures of the, latonduines were elucidated by analysis of spectroscopic data and confirmed by the total synthesis of latonduine A (6). It is proposed that ornithine is the biogenetic precursor to the aminopyrimidine fragment of the latonduines.}, keywords = {COMPOUND, DEBROMOHYMENIALDISINE, HYMENIALDISINE, INHIBITION, STEVENSINE}, isbn = {1523-7060}, url = {://000184257600039}, author = {Linington, R. G. and Williams, D. E. and Tahir, A. and Van Soest, R. and Andersen, R. J.} } @article {5075, title = {New mode of coordination for the dinitrogen ligand: Formation, bonding, and reactivity of a tantalum complex with a bridging N-2 unit that is both side-on and end-on}, journal = {Journal of the American Chemical Society}, volume = {123}, number = {17}, year = {2001}, note = {ISI Document Delivery No.: 428CCTimes Cited: 84Cited Reference Count: 91}, month = {May}, pages = {3960-3973}, type = {Article}, abstract = {The reaction of a mixture of 1 equiv of PhPH2 and 2 equiv of PhNHSiMe2CH2Cl with 4 equiv of (BuLi)-Li-n followed by the addition of THF generates the lithiated ligand precursor [NPN]Li-2. (TKF)2(where [NPN] = PhP(CH2SiMe2NPh)(2)). The reaction of [NPN]Li-2. (THF)(2) with TaMe3Cl2 produces [NPN]TaMe3, which reacts under HZ to yield the diamagnetic dinuclear Ta(IV! tetrahydride ([NPN]Ta)(2)(mu -H)4 This hydride reacts with N-2 with the loss of H-2 to produce ([NPN]Ta(mu -H))(2)(mu-eta (1):eta (2)-N-2), which was characterized both in solution and in the solid state, and contains strongly activated Nz bound in the unprecedented side-on end-on dinuclear bonding mode. A density functional theory calculation on the model complex [(H3P)(H2N)(2)Ta(mu -H)](2)-mu-eta (1):eta (2)-N-2) provides insight into the molecular orbital interactions involved in the side-on end-on bonding mode of dinitrogen. The reaction of ([NPN]Ta(mu -H))(2)(mu-eta (1):eta (2)-N-2) with propene generates the end-on bound dinitrogen complex ([NPN]Ta(CH2CH2CH3))(2)(mu-eta (1):eta (1)-N-2), and the reaction of [NPN]Li-2. (THF)(2) with NbCl3-(DME) generates the end-on bound dinitrogen complex ([NPN]NbCl)(2)(mu-eta (1):eta (1)-N-2). These two end-on bound dinitrogen complexes provide evidence that the bridging hydride ligands are responsible for the unusual bonding mode of dinitrogen in ([NPN]Ta(mu -H))(2)(mu-eta (1):eta (2)-N-2). The dinitrogen moiety in the side-on end-on mode is amenable to functionalization; the reaction of ([NPN]Ta(mu -H))(2)(mu-eta (1):eta (2)-N-2) with PhCH2Br results in C-N bond formation to yield [NPN]Ta(mu-eta (1):eta (2)-N2CH2Ph)(mu -H)(2)TaBr[NPN]. Nitrogen-15 NMR spectral data an provided for all the tantalum-dinitrogen complexes and derivatives described.}, keywords = {CHEMISTRY, CLEAVAGE, COMPOUND, CRYSTAL-STRUCTURE, MOLECULAR-STRUCTURES, NITROGEN-FIXATION, {ACTIVATION}, isbn = {0002-7863}, url = {://000168442700013}, author = {Fryzuk,Michael D. and Johnson, S. A. and Patrick, B. O. and Albinati, A. and Mason, S. A. and Koetzle, T. F.} } @article {3754, title = {Stereoselective synthesis of new chlorophyll A related antioxidants isolated from marine organisms}, journal = {Journal of Organic Chemistry}, volume = {61}, number = {7}, year = {1996}, note = {ISI Document Delivery No.: UD653Times Cited: 39Cited Reference Count: 37}, month = {Apr}, pages = {2501-2510}, type = {Article}, abstract = {A new class of natural antioxidants, chlorophyll a related chlorins 3, 4(S), 4(R), 5(R), 6, 7, 8, and 9, have been synthesized from a chlorophyll a degradation product, pheophorbide a methyl ester (1). Claisen-type intramolecular condensation of pyropheophorbide a methyl ester (2) afforded the common intermediate enol 3. Chlorin 1 and enol 3 have a propensity to undergo exocyclic ring opening by ionic bases. The organic base DBU was found to be an efficient reagent for promoting the asymmetric hydroxylation of these chlorins, using N-sulfonyloxaziridines, without cleavage of the exocyclic rings. Model studies for hydroxylactonization have shown that periodate oxidation of hydroxy ketone 10 stereoselectively and predominantly forms hydroxy lactone 17(S). Periodate oxidation of alpha-hydroxy 1,3-diketone 4(R) and/or 4(S) to furnish hydroxy lactone 5(R) and diketone 7 was found out to be regioselective, and the site of reaction depends on the appropriate choice of reaction media. H-1 NMR spectra have provided information on the absolute configuration of diastereomers at the C-13(2) or C-15(1) position.}, keywords = {2-SULFONYLOXAZIRIDINES, CHEMISTRY, COMPOUND, DERIVATIVES, enol, HYDROXYLATION, ORIGINS, RCI, RUDITAPES-PHILIPPINARUM}, isbn = {0022-3263}, url = {://A1996UD65300039}, author = {Ma, L. F. and Dolphin, D.} } @article {3753, title = {Synthesis and spectral studies of natural chlorins having antioxidative activity}, journal = {Pure and Applied Chemistry}, volume = {68}, number = {3}, year = {1996}, note = {ISI Document Delivery No.: UM994Times Cited: 3Cited Reference Count: 1510th International Conference on Organic SynthesisDEC 11-16, 1994BANGALORE, INDIAInt Union Pure \& Appl Chem, Organ Chem Div, Indian Natl Sci Acad, Natl Organ Symp Trust, India, Indian Inst Sci, Jawaharlal Nehru Ctr Adv Sci Res}, month = {Mar}, pages = {765-769}, type = {Proceedings Paper}, abstract = {Starting from pheophorbide a methyl ester (1), a degradation product of chlorophyll a, novel natural antioxidants of chlorophyll a related chlorins 3, 5(S), 5(R), 8(R), 9-13 have been synthesized in high yields. Key steps involve formation of 5(R) and 5(8) via a DBU-promoted asymmetric hydroxylation of 3, and regioselective periodate oxidations of 5 to 8(R) and 9.}, keywords = {COMPOUND, enol, RUDITAPES-PHILIPPINARUM}, isbn = {0033-4545}, url = {://A1996UM99400059}, author = {Ma, L. F. and Dolphin, D.} } @article {2773, title = {PREPARATION AND CHARACTERIZATION OF THE OSMIUM CLUSTER COMPLEXES H2OS3(CO)8L(ETFCPCME) (L=CO OR PET2FC) AND H2OS3(CO)8[(ETA-C5H3PET2)FE(ETA-C5H4)]}, journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie}, volume = {71}, number = {3}, year = {1993}, note = {ISI Document Delivery No.: KU982Times Cited: 4Cited Reference Count: 35}, month = {Mar}, pages = {399-409}, type = {Article}, abstract = {{Thermolysis of Os3(CO)11](PEt2Fc) (Fc = (eta-C5H4)Fe(eta-C5H5)) in octane for 8 h affords H2Os3(CO)9(EtFcPCMe), 10, and H2Os3(CO)8[(eta-C5H3PEt2)Fe(eta-C5H4)], 9e, in 15 and 65\% yield, respectively. Heating Os3(CO),2 and PEt2Fc in 1:2 molar ratio in xylene for 10 h gives two isomers of H2Os3(CO)8(PEt2Fc)(EtFcPCMe), 11, in about 40\% yield. Two crystalline modifications of the complex 9e have been obtained from the same solvent: 9eA, triclinic}, keywords = {BENZYNE, BOND, CHEMISTRY, COMPOUND, COORDINATION, LIGANDS, MODE, RAY CRYSTAL-STRUCTURES, REACTIVITY, TRIOSMIUM CLUSTERS}, isbn = {0008-4042}, url = {://A1993KU98200020}, author = {Cullen, W. R. and Rettig, S. J. and Zheng, T. C.} } @article {7303, title = {ORGANOMETALLIC NITROSYL CHEM .52. A UNIQUE MU-ETA-1-ETA-2-NO LIGAND IN A BIMETALLIC ALKYLIDENE NITROSYL COMPLEX OF MOLYBDENUM}, journal = {Journal of the American Chemical Society}, volume = {114}, number = {17}, year = {1992}, note = {ISI Document Delivery No.: JH996Times Cited: 15Cited Reference Count: 18}, month = {Aug}, pages = {6922-6923}, type = {Note}, keywords = {ABSTRACTION, CHEMISTRY, COMPOUND, DOUBLE-BOND, MOLECULAR-STRUCTURE, REACTIVITY, TETRANITROSYL, TUNGSTEN}, isbn = {0002-7863}, url = {://A1992JH99600051}, author = {Legzdins,Peter and Rettig, S. J. and Veltheer, J. E.} }