The versatile reactivity of cyclo-(P5tBu4)- with complexes of the nickel triad

Na[cyclo-(P(5)tBu(4))] (1) reacts with [NiCl(2)(PEt(3))(2)] and [PdCl(2)(PMe(2)Ph)(2)] with elimination of tBuCl and formation of the corresponding metal(0) cyclopentaphosphene complexes [Ni{cyclo-(P(5)tBu(3))}(PEt(3))(2)] (2) and [Pd{cyclo-(P(5)tBu(3))}(PMe(2)Ph)(2)] (3). In contrast, complexes with the more labile triphenylphosphane ligand, such as [MCl(2)(PPh(3))(2)] (M=Ni, Pd), react with 1 with formation of [NiCl{cyclo-(P(5)tBu(4))}(PPh(3))] (4) and [Pd{cyclo-(P(5)tBu(4))}(2)] (5), respectively, in which the cyclo-(P(5)tBu(4)) ligand is intact. In the case of palladium, the cyclopentaphosphene complex [Pd{cyclo-(P(5)tBu(3))}(PPh(3))(2)] (6) in trace amounts is also formed. However, [Ni{cyclo-(P(5)tBu(4))}(2)] (7) is easily obtained by reaction of two equivalents of 1 and one equivalent of [NiCl(2)(bipy)] at room temperature. Complex 7 rearranges on heating in n-hexane or toluene to the previously unknown [Ni{cyclo-(P(5)tBu(4))PtBu}{cyclo-(P(4)tBu(3))}] (8), which presumably is formed via the intermediate [Ni{cyclo-(P(5)tBu(4))}{cyclo-(P(4)tBu(3))PtBu}], which, after an unexpected and unprecedented phosphanediide migration, gives 8, but always as an inseparable mixture with 7. In the reaction of 1 with [PtCl(2)(PPh(3))(2)], ring contraction and formation of [PtCl{cyclo-(P(4)tBu(3))PtBu}(PMe(2)Ph)] (9) is observed. Complexes 3-5 and 7-9 were characterised by (31)P NMR spectroscopy, and X-ray structures were obtained for 5-9.     

一株红树内生真菌Penicillium sp.(ZZF29#)次级代谢产物分离与鉴定

研究了一株药用红树内生真菌Penicillium sp.(ZZF29#)的次级代谢产物。用硅胶柱层析、制备薄层层析和重结晶等方法,从该菌发酵液的乙酸乙酯相中分离获得8种单体化合物,运用现代波谱技术并与文献数据对照,鉴定其结构分别为:环(苯丙-丙)二肽(1)、环(苯丙-甘)二肽(2)、环(苯丙-苯丙)二肽(3)、环(苯丙-酪)二肽(4)、大黄素(5)、大黄素甲醚(6)、麦角甾醇(7)和过氧化麦角甾醇(8)。     

Activity and Synergistic Antimicrobial Activity Between Diketopiperazines Against Bacteria In Vitro

The aim of the present study was to determine the synergistic effects of diketopiperazines [cyclo-(l-Pro-l-Leu) (1), cyclo-(d-Pro-l-Leu) (2), and cyclo-(d-Pro-l-Tyr) (3)] purified from a Bacillus sp. N strain associated with entomopathogenic nematode Rhabditis (Oscheius) sp. on the growth of bacteria. The minimum inhibitory concentration and minimum bactericidal concentration of the diketopiperazines was compared with that of the standard antibiotics. The synergistic antibacterial activities of the combination of diketopiperazines against pathogenic bacteria were assessed using the checkerboard assay and time?Ckill methods. The results of the present study showed that the combination effects of diketopiperazines were predominately synergistic (FIC index <0.5). Furthermore, time?Ckill study showed that the growth of the tested bacteria was completely attenuated with 4?C12?h of treatment with 50:50 ratios of diketopiperazines. These results suggest that the combination of diketopiperazines may be microbiologically beneficial. The three diketopiperazines are nontoxic to normal human cell line (L231 lung epithelial) up to 200?m???g/ml. The in vitro synergistic activity of cyclo-(l-Pro-l-Leu), cyclo-(d-Pro-l-Leu), and cyclo-(d-Pro-l-Tyr) against bacteria is reported here for the first time. These findings have potential implications in delaying the development of resistance as the antibacterial effect is achieved with lower concentrations of both drugs (diketopiperazines).     

Coordination chemistry of the cyclo-(P(5)tBu(4))(-) ion: monomeric and oligomeric copper(I), silver(I) and gold(I) complexes

[Na{cyclo-(P(5)tBu(4))}] (1) reacts with [CuCl(PCyp(3))(2)] (Cyp=cyclo-C(5)H(9)) and [CuCl(PPh(3))(3)] (1:1) to give the corresponding copper(I) complexes with a tetra-tert-butylcyclopentaphosphanide ligand, [Cu{cyclo- (P(5)tBu(4))}(PCyp(3))(2)] (2) and [Cu{cyclo-(P(5)tBu(4))}(PPh(3))(2)] (3). The CuCl adduct of 2, [Cu(2)(mu-Cl){cyclo-(P(5)tBu(4))}(PCyp(3))(2)] (4), was obtained from the reaction of 1 with [CuCl(PCyp(3))(2)] (1:2). Compounds 2 and 3 rearrange, even at -27 degrees C, to give [Cu(4){cyclo- (P(4)tBu(3))PtBu}(4)] (5), in which ring contraction of the [cyclo-(P(5)tBu(4))](-) anion has occurred. The reaction of 1 with [AgCl(PCyp(3))](4) or [AgCl(PPh(3))(2)] (1:1) leads to the formation of [Ag(4){cyclo-(P(4)tBu(3))PtBu}(4)] (6). Intermediates, which are most probably mononuclear, "[Ag{cyclo-(P(5)tBu(4))}(PR(3))(2)]" (R=Cyp, Ph) could be detected in the reaction mixtures, but not isolated. Finally, the reaction of 1 with [AuCl(PCyp(3))] (1:1) yielded [Au{cyclo-(P(5)tBu(4))}(PCyp(3))] (7), whereas an inseparable mixture of [Au(3){cyclo-(P(5)tBu(4))}(3)] (8) and [Au(4){cyclo-(P(4)tBu(3))PtBu}(4)] (9) was obtained from the analogous reaction with [AuCl(PPh(3))]. Complexes 3-7 were characterised by (31)P NMR spectroscopy, and X-ray crystal structures were determined for 3-9.     

A comparison of electron impact and field ionization spectra of some 2,5-diketopiperazines

The mass spectra of cyclo-(Gly-Leu), cyclo-(Gly-Tyr), cyclo-(Ala-Tyr), cyclo-(Leu-Tyr), cyclo-(Val-Phe) and cyclo-(Leu-Phe) are presented. The use of high resolution mass measurements and metastable analysis allows the proposal of some general fragmentation mechanisms. The dominant features in the mass spectra of 2,5-diketopiperazines are fragments corresponding to cleavages of sidechains and the rupture of the piperazine-2,5-dione ring. The characteristic fragments may be used in the identification of any 2,5-diketopiperazines by mass spectrometry.     

Li(thf)3cyclo-(P4tBu4CH)]--synthesis, molecular structure and dynamic behaviour

[Li(thf)3cyclo-(P4tBu4CH)] (2-Li), containing the first tetraphosphacyclopentanide anion cyclo-(P4tBu4CH)- (2), was prepared, and its dynamic behaviour in solution analysed by variable-temperature 31P NMR spectroscopy.     

In situ synthesis of nickel tiara-like clusters with two different thiolate bridges

Four nickel clusters, cyclo-[{Ni(μ-S(i)Pr)(μ-SMe)}(6)] (1), cyclo-[{Ni(μ-StBu)(μ-SMe)}(6)] (2), cyclo-[{Ni(μ-S(i)Pr)(μ-SEt)}(6)] (3) and cyclo-[{Ni(μ-StBu)(μ-SEt)}(10)] (4), based on thiolate ligands have been successfully synthesized and characterized by elemental analysis, FT-IR spectra, UV-vis-NIR spectra, powder X-ray diffraction and single-crystal X-ray diffraction. Intriguingly, the SMe and SEt ligands are generated from solvothermal in situ ligand synthesis through the cleavage of the S-S bond respectively. The four nickel thiolate clusters exhibit tiara-like frameworks consisting of two different types of thiolate ligands.     

Ferromagnetic spin coupling between endohedral metallofullerene La@C82 and a cyclodimeric copper porphyrin upon inclusion

The cyclic host cyclo-[P(Cu)](2) carrying two covalently connected Cu(II) porphyrin units can accommodate La@C(82), a paramagnetic endohedral metallofullerene, in its cavity to form the inclusion complex cyclo-[P(Cu)](2)?La@C(82), which can be transformed into the caged complex cage-[P(Cu)](2)?La@C(82) by ring-closing olefin metathesis of its side-chain olefinic termini. On the basis of electron spin resonance (ESR) and electron spin transient nutation (ESTN) studies, cyclo-[P(Cu)](2)?La@C(82) is the first ferromagnetically coupled inclusion complex featuring La@C(82), whereas cage-[P(Cu)](2)?La@C(82) is ferrimagnetic.     

Carboracycles: Macrocyclic Compounds Composed of Carborane Icosahedra Linked by Organic Bridging Groups

A family of macrocyclic compounds are described, together with their precursors. These cycles are composed of icosahedral carboranes linked via their carbon vertices through 1,3-trimethylene, alpha,alpha'-1,3-xylylene, or alpha,alpha'-2,6-lutidylene groups. The compounds cyclo-(1,3-trimethylene-1',2'-closo-1',2'-C(2)B(10)H(10))(4) (6a), cyclo-(1,3-trimethylene-1',2'-closo-9',12'-dimethyl-1',2'-C(2)B(10)H(8))(4) (6b), cyclo-(1,3-trimethylene-1',2'-closo-1',2'-C(2)B(10)H(10))(3) (9), cyclo-(alpha,alpha'-1,3-xylylene-1',2'-closo-1',2'-C(2)B(10)H(10))(2) (11a), cyclo-(alpha,alpha'-1,3-xylylene-1',7'-closo-1',7'-C(2)B(10)H(10))(2) (11b), cyclo-(alpha,alpha'-1,3-xylylene-1',7'-closo-9',10'-dimethyl-1,7-C(2)B(10)H(8))(2) (11c), cyclo-(alpha,alpha'-1,3-xylylene-1',2'-closo-1',2'-C(2)B(10)H(10))(4) (12), cyclo-(alpha,alpha'-1,3-xylylene-1',7'-closo-1',7'-C(2)B(10)H(10))(3) (13), cyclo-(alpha,alpha'-2,6-lutidylene-1',7'-closo-1',7'-C(2)B(10)H(10))(2) (19), and cyclo-(alpha,alpha'-2,6-lutidylene N-oxide-1',7'-closo-1',7'-C(2)B(10)H(10))(2) (20) have been synthesized. The structures of 6a, 6b, 9, 11a, 11b, 11c, 12, and 19 have been determined by X-ray crystallography. Crystal data: for 6a, triclinic, space group P&onemacr;, a = 11.131(2) ?, b = 12.642(2) ?, c = 12.996(2) ?, alpha = 84.383(6) degrees, beta = 65.884(6) degrees, gamma = 97.292(5) degrees, Z = 1, R = 0.079; for 6b, monoclinic, space group P2(1)/a, a = 13.500(2) ?, b = 31.141(3) ?, c = 13.831(2) ?, beta = 99.90(1) degrees, Z = 2, R = 0.097; for 11a, monoclinic, space group C2/c, a = 14.5682(8) ?, b = 14.5046(8) ?, c = 16.1998(8) ?, beta = 95.631(2) degrees, Z = 4, R = 0.081; for 11b, monoclinic, space group P2(1)/n, a = 11.650(2) ?, b = 10.606(2) ?, c = 11.730(2) ?, beta = 104.951(6) degrees, Z = 2, R = 0.069; for 11c, orthorhombic, space group Pbca, a = 12.532(2) ?, b = 14.271(2) ?, c = 18.143(3) ?, Z = 4, R = 0.076; for 19, orthorhombic, space group Pcab (No. 61, standard setting Pbca), a = 11.0428(6) ?, b = 11.3785(6) ?, c = 22.533(1) ?, Z = 4, R = 0.074.     

The reactivity of cyclo-(P5tBu4)- towards group 13, 14 and 15 metal chlorides: complexation and formation of cyclooligophosphanes, [cyclo-(P5tBu4)]2 and [cyclo-(P4tBu3)PtBu]2, by reductive elimination

[Na(THF)4][cyclo-(P5tBu4)] (1) reacts with Et2AlCl and GeCl4 to give Et2Al[cyclo-(P5tBu4)](THF) (2) and, in low yield, GeCl3[cyclo-(P5tBu4)], respectively, while the reaction of 1 with SnCl2, PbCl2 or BiCl3 results in the formation of the structural isomers [cyclo-(P5tBu4)]2 (3) and [cyclo-(P4tBu3)PtBu]2 (4)(besides other cyclic phosphanes) and elemental metal.     

Growth format, electronic architecture, magnetic, and optical properties of aromatic cyclo-Cu3Au3 homotops

Bimetallic Cu(3)Au(3) clusters have been investigated using electronic structure calculation techniques (DFT) to understand their electronic, magnetic, and optical properties as well as the geometrical structures. The most stable homotop is the planar cyclo-[Cu(3)(micro-Au)(3)] form consisting of a triangular positively charged Cu(3) structural core with negatively charged Au atoms occupying exposed positions. This structure is characterized by the maximum number of heterobonds and peripheral positions of Au atoms. Possible growth formats of the cyclo-[Cu(3)(micro-Au)(3)] homotops have been explored following both the edge-capping and the stepwise metal atom substitution mechanism. The bonding pattern along with the density of states (DOS) plots of the cyclo-[Cu(3)(micro-Au)(3)] homotop are thoroughly analyzed and compared with those of the pure cyclo-[Cu(3)(micro-Cu)(3)] and cyclo-[Au(3)(micro-Au)(3)] clusters. Particular attention was paid on the stability of these bimetallic clusters in relation with the ring-shaped electron density distribution (aromaticity). It was found that all 3-membered metal rings exhibit significant aromatic character, which was verified by a number of established criteria of aromaticity, such as structural, energetic, magnetic (NICS profiles), and out-of-plane ring deformability criteria. The NICS (1) values correlate well with the out-of-plane ring deformation energy. Finally, a comprehensive analysis of the optical spectra of the CuAu, Cu(2), and Au(2) diatomics and the cyclo-[Cu(3)(micro-Au)(3)], cyclo-[Cu(3)(micro-Cu)(3)], and cyclo-[Au(3)(micro-Au)(3)] clusters placed the electronic assignments of the optical transitions on a firm footing.     

Diastereoselective synthesis of 2-amino-4-phosphonobutanoic acids by conjugate addition of lithiated Schöllkopf's bislactim ethers to vinylphosphonates

Conjugate additions of lithiated bislactim ethers derived from cyclo-[Gly-Val] and cyclo-[Ala-Val] to alpha-, beta-, or alpha,beta-substituted vinylphosphonates allow direct and stereoselective access to a variety of 3- or 4-monosubstituted and 2,3-, 2,4-, or 3,4-disubstituted 2-amino-4-phosphonobutanoic acids (AP4 derivatives) in enantiomerically pure form. The relative stereochemistry was assigned by X-ray diffraction analysis or NMR study of 1,2-oxaphosphorinane derivatives. Competitive eight-membered "compact" and "relaxed" transition-state structures are invoked to rationalize the stereochemical outcome of the conjugate additions.     

海洋放线菌Streptomyces sp. V5产生的一个新的八元环内酯

海洋放线菌Streptomyces sp. V5分离自南中国海红树根部土壤, 从其培养液分离获得一个新的八元环内酯octalactin C (A), 以及四个已知化合物2-甲基-3-呋喃甲酸(B)、环(脯-亮)二肽(C)、环(丙-缬)二肽(D)和尿嘧啶(E). 通过完整的波谱数据解析了它们的结构.     

Two new metabolites of a marine endophytic fungus (No. 1893) from an estuarine mangrove on the South China Sea coast

The endophytic fungus No. 1893 was isolated from the dropper of Kandelia candel from an estuarine mangrove on the South China Sea coast. The ethyl acetate extract of the fermentation broth of this fungus strain exhibited cytotoxicity toward NCI4460 and Bel-7402, and high activities against Heliothis armigera (Hühner) and Sinergasilus spp. Two new lactones, 1893A (1) and B (2), together with 5-(p-hydroxybenzyl)hydantoin and two cyclodipeptides, cyclo-(Ser-Leu) and cyclo-(Phe-Gly), were isolated from the extract. Their structures were determined by spectroscopic experiments, including X-ray diffraction.     

Reactivity of cyclooligophosphanes: synthesis and structural characterisation of cyclo-1,4-(BH3)2(P4Ph4CH2) and cyclo-1,2-(BH3)2(P5Ph5)

The borane complexes cyclo-1,4-(BH3)2(P4Ph4CH2) (3) and cyclo-1,2-(BH3)2(P5Ph5) (4) were prepared by reaction of cyclo-(P4Ph4CH2) and cyclo-(P5Ph5) with BH3(SMe2). Only the 2:1 complexes 3 and 4 were isolated, even when an excess of the borane source was used. In solution, 3 exists as a mixture of the two diastereomers (R(P)*,S(P)*,S(P)*,R(P)*)-(+/-)-3 and (R(P)*,R(P)*,R(P)*,R(P)*)-(+/-)-3. However, in the solid state the (R(P)*,S(P)*,S(P)*,R(P)*)-(+/-) diastereomer is the major stereoisomer. Similarly, while only one isomer of 4 is observed in its X-ray structure, NMR spectroscopic investigations reveal that it forms a complex mixture of isomers in solution. 3 may be deprotonated with tBuLi to give the lithium salt cyclo-1,4-(BH3)2(P4Ph4CHLi) (3 x Li), though this could not be isolated in pure form.     

南海红树内生真菌1947号次级代谢产物的研究

红树植物是一类生长于潮间带的乔灌木的通称。近年来,国内外对红树内生真菌代谢产物的研究呈快速发展趋势。本课题组自上世纪90年代以来开始研究南海红树内生真菌代谢产物,迄今已从南海红树内生真菌分离得到许多有意义的代谢产物[1-5]。编号为1947号的内生真菌分离自香港江口红     

Single turn peptide alpha helices with exceptional stability in water

Cyclic pentapeptides are not known to exist in alpha-helical conformations. CD and NMR spectra show that specific 20-membered cyclic pentapeptides, Ac-(cyclo-1,5) [KxxxD]-NH(2) and Ac-(cyclo-2,6)-R[KxxxD]-NH(2), are highly alpha-helical structures in water and independent of concentration, TFE, denaturants, and proteases. These are the smallest alpha-helical peptides in water.     

Synthesis and molecular structure of the first rhodium(I) complex containing a tetra-tert-butylcyclopentaphosphanide ligand

Na[cyclo-(P(5)(t)Bu(4))] (1) reacts with [RhCl(PPh(3))(3)] (1:1) to give the first rhodium(I) complex with a tetra-tert-butylcyclopentaphosphanide ligand, [Rh{cyclo-(P(5)(t)Bu(4))}(PPh(3))(2)] (2). 2 was characterized by NMR ((1)H, (13)C, (31)P), MS, IR, and X-ray structure determination.     

Weed growth inhibitors from Aspergillus fischeri TISTR 3272

Chloroform and ethyl acetate extracts of Aspergillus fischeri TISTR 3272 showed good growth inhibitory activity on Mimosa pigra and Echinochloa crus-galli. Bioassay-directed fractionation of the active extracts led to the isolation of five known compounds, (+)-terrein (1), (-)-6-hydroxymellein (2), two diketopiperazines (cyclo-(S-Pro-S-Leu) (3) and cyclo-(S-Pro-S-Val) (4)) and butyrolactone I (5). Compounds 2-5 were reported for the first time in this fungus. Their structural determinations were based on analyses of spectroscopic data and their weed growth inhibitory effects were assessed.     

Molecular mechanics (MM2) calculations on peptides and on the protein Crambin using the CYBER 205

The MM2 potential functions for amides and peptides have been further extended by examining the experimental crystal structures for cyclo-(-Ala-Ala-Gly-Gly-Ala-Gly-), I, and cyclo-(-Ala-Ala-Gly-Ala-Gly-Gly-), II. The force field obtained was then applied to a study of the structure of the hydrophobic protein Crambin, for which a high resolution crystal structure is available. The energy minimization was carried out using a version of MM2 adapted to the CYBER 205.