Band 71, Heft 2

A mixture of two compounds with potent antiplasmodial activity in vitro against the W2 strain of Plasmodium falciparum (half maximal inhibitory concentration, 1.12 μg/mL) was obtained in a previous investigation of the CH 2 Cl 2 -MeOH extract of the seeds of Salacia longipes var. camerunensis. Separation by column chromatography led now to the isolation of salaterpene E ( 1 ) and (1 R ,2 R ,4 S ,5 S ,6 R ,7 R ,9 S ,10 R )-2-acetoxy-1,6,9-tribenzoyloxy-4-hydroxy-dihydro- β -agarofuran ( 2 ). The structure of 1 was elucidated by spectroscopic analysis, and its absolute configuration was established unambiguously by means of single-crystal X-ray diffraction. Also the absolute configurations of the recently described salaterpenes A ( 2a ) and D ( 2b ) were determined by this method using the anomalous scattering of the oxygen atoms only.

A variety of N -acyl- N -(4-chlorophenyl)-4-nitrobenzenesulfonamides ( 1a – e ) were synthesized in one pot from 4-chloroaniline under solvent-free conditions and have been developed as chemoselective N-acylation reagents. Selective protection of primary amines in the presence of secondary amines, acylation of aliphatic amines in the presence of aryl amines, and monofunctionalization of primary-secondary diamines as well as selective N-acylation of amino alcohols using these reagents are described. All of the acylation reactions were carried out in water as a green solvent. High stability and easy preparation of these acylating reagents are other advantages of this method.

Three new complexes of Cu(II) halides (Cl, Br) with 1-methylimidazole (MIm), [Cu(MIm) 4 ]Br 2 ( 1 ), [Cu(MIm) 4 Br]Br · H 2 O ( 2 ), and [Cu(MIm) 6 ]Cl 2 · 2H 2 O ( 3 ) have been synthesized in ethanol. Their crystal structures have been determined by single-crystal X-ray diffraction. FT-IR spectroscopy, mass spectrometry, and thermal analyses were applied to characterize the compounds.

Calix[4]arene-thiourea and -tetraamide naked-eye receptors do not show any tendency to self-aggregation and are highly sensitive towards small monoanions; association constants in DMSO for halogenides (chloride to iodide) and HSO 4 – are <200 m –1 . Basic anions deprotonate both receptors leading to a high and selective optical readout. Binding constants for carboxylates, fluoride, and dihydrogen phosphate are three orders of magnitude higher (~10 5 m –1 ) in case of the tetrathiourea receptor.

Treatment of [RuCl 2 (PPh 3 ) 3 ] with equimolar amounts of 2,4-pyridinedicarboxylic acid (2,4-dipicH 2 ) in the presence of Et 3 N afforded a tetranuclear complex [Ru( μ -2,4-dipic)(PPh 3 ) 2 ] 4 ( 1 ) as red crystals. The crystal and molecular structure of [Ru( μ -2,4-dipic)(PPh 3 ) 2 ] 4 ·CHCl 3 ·8H 2 O ( 1 ·CHCl 3 ·8H 2 O) was determined by single-crystal X-ray diffraction. Each ruthenium center in 1 is six-coordinated with two phosphorus atoms from triphenylphosphine ligands, one nitrogen atom from a pyridyl moiety and three oxygen atoms from two 2,4-dipic 2– ligands. 2,4-Pyridinedicarboxylate dianions (2,4-dipic 2– ) act as bridging ligands to form the stable tetranuclear metallamacrocyclic compound. The electrochemical properties of 1 were also investigated.

Original first-principles calculations were performed to study the structural and electronic properties of quaternary B x Al y Ga 1– x – y N compounds, using the non-relativistic full-potential linearized augmented plane wave method as employed in the W ien 2k code. For the exchange-correlation potential, local density approximation and generalized gradient approximation have been used to calculate theoretical lattice parameters, bulk modulus, and their pressure derivatives. Non-linear variation with compositions x and y of the lattice parameter, bulk modulus, and direct and indirect band gaps have been found. The calculated bowing of the fundamental band gaps is in good agreement with the available experimental and theoretical values.

Treatment of P 4 with one equivalent of Li[Si t Bu 3 ] leads to the formation of a number of oligo-phosphanes and -phosphides, e.g. the bicyclo[1.1.0]tetraphosphane P 4 (Si t Bu 3 ) 2 , the heptaphosphanortricyclane P 7 (Si t Bu 3 ) 3 , the tetraphosphides Li 3 [P(PSi t Bu 3 ) 3 ] (Li 3 [2a] ), and the pentaphosphacyclopentadienide Li[P 5 ]. From this reaction we could isolate single crystals of Li 3 [2a] . However, this reaction took another course in the presence of Li[OSi t Bu 3 ]. When P 4 was treated with one equivalent of Li[Si t Bu 3 ] in the presence of Li[OSi t Bu 3 ], the heptaphosphanortricyclanide Li[P 7 (Si t Bu 3 ) 2 ] (Li [8a] ) was formed. Single crystals of the cluster {Li 4 (C 6 H 6 )(OSi t Bu 3 ) [8a] 3 }·C 6 H 6 (orthorhombic, space group Pca 2 1 ) were isolated from the reaction mixture at ambient temperature. This cluster compound consists of three chiral Li[P 7 (Si t Bu 3 ) 2 ] units, one silanolate Li[OSi t Bu 3 ], and one benzene molecule. We further investigated the degradation reaction of the bicyclo[1.1.0]tetraphosphane P 4 (Si t Bu 3 ) 2 . After heating a benzene solution to 60 °C for 24 h, we found 100 % conversion of P 4 (Si t Bu 3 ) 2 , and P 7 (Si t Bu 3 ) 3 (monoclinic, space group P 2 1 / c ) and t Bu 3 SiPH 2 were formed.

A facile metal-free approach to the synthesis of imidazo[1,2- a ]pyridine was developed through a tandem reaction of Michael addition and oxidative coupling. Iodine– t- butyl hydroperoxide–pyridine was found to be a green and efficient catalytic system for this approach.

The phosphide oxides La 3 Cu 4 P 4 O 2 and La 5 Cu 4 P 4 O 4 Cl 2 were synthesized from lanthanum, copper(I) oxide, red phosphorus, and lanthanum(III) chloride through a ceramic technique. Single crystals can be grown in a NaCl/KCl flux. Both structures were refined from single crystal X-ray diffractometer data: I 4/ mmm , a = 403.89(4), c = 2681.7(3) pm, wR 2 = 0.0660, 269 F 2 values, 19 variables for La 3 Cu 4 P 4 O 2 and a = 407.52(5), c = 4056.8(7) pm, wR 2 = 0.0905, 426 F 2 values, 27 variables for La 5 Cu 4 P 4 O 4 Cl 2 . Refinement of the occupancy parameters revealed full occupancy for the oxygen sites in both compounds. The structures are composed of cationic (La 2 O 2 ) 2+ layers and covalently bonded (Cu 4 P 4 ) 5– polyanionic layers with metallic characteristics, and an additional La 3+ between two adjacent (Cu 4 P 4 ) 5– layers. The structure of La 5 Cu 4 P 4 O 4 Cl 2 comprises two additional LaOCl slabs per unit cell. Temperature-dependent magnetic susceptibility studies revealed Pauli paramagnetism. The phosphide substructure of La 3 Cu 4 P 4 O 2 was studied by 31 P solid state NMR spectroscopy. By using a suitable dipolar re-coupling approach the two distinct resonances belonging to the P 2 4– and the P 3– units could be identified.

Crystals of Li A [N(CN) 2 ] 2 were obtained from the reaction of LiCl and A Cl ( A = K or Rb) with Ag[N(CN) 2 ] in water and subsequent evaporation of the filtered solution at 80 °C under normal atmospheric conditions. Crystals of the title compound form thin rectangular plates that are transparent, colorless, and very fragile. Single-crystal structure analyses have shown that both compounds are isotypic and adopt the tetragonal space group I 4/ mcm (no. 140, Z = 4) with the cell parameters a = 701.53(12) and c = 1413.7(5) pm for LiK[N(CN) 2 ] 2 and a = 730.34(10) and c = 1414.4(4) pm for LiRb[N(CN) 2 ] 2 . The crystal structure is described and compared to that of the pseudo-binary alkali metal dicyanamides.

A procedure was empirically developed to prepare the compound LiK 2 [SCN] 3 , which forms colorless, transparent, very fragile, and extremely hygroscopic thin rectangular plates. Its unique crystal structure was determined by single-crystal X-ray diffraction. LiK 2 [SCN] 3 adopts the orthorhombic space group Pna 2 1 (no. 33, Z = 4) with the cell parameters a = 1209.32(9), b = 950.85(9), and c = 849.95(6) pm.