Structural development of benzhydrol-type 1'-acetoxychavicol acetate (ACA) analogs as human leukemia cell-growth inhibitors based on quantitative structure-activity relationship (QSAR) analysis

Benzhydrol-type analogs of 1'-acetoxychavicol acetate (ACA) were developed as inhibitors of human leukemia HL-60 cell growth based on quantitative structure-activity relationship (QSAR) analysis. An analog containing an anthracenyl moiety (8) was a potent inhibitor with the IC(50) value of 0.12 microM.     

Comparison of molecular conductance between planar and twisted 4-phenylpyridines by means of two-dimensional phase separation of tetraphenylporphyrin templates at a liquid-HOPG interface

Tetraphenylporphyrin (TPP) rhodium chlorides coordinated by planar and twisted 4-phenylpyridine derivatives were synthesized. An STM image was taken by a 2-D phase separation technique and the conductance was evaluated. Difference in apparent height between these phenylpyridines reflects the conductance ratio of ligands.     

Preparation and electrochemical properties of SAM of alkanethiols functionalized with 2-aza[3]ferrocenophane on gold electrode

Thiols functionalized with N-aryl[3]azaferrocenophane formulated as HS-(CH₂)_n-N(CH₂Cp)₂Fe (1: n = 6, 2: n = 8, 3: n = 10, 4: n = 12) and disulfide obtained by oxidation of 4 (5) were synthesized via three or four steps reactions starting from 1,1′-ferrocenedimethanol, 4-aminophenol, and α,ω-aklanedithiol. Self-assembled monolayers (SAMs) of these thiols and disulfide on gold electrode were prepared by immersing the electrode in MeCN solutions of the compounds. Cyclic voltammograms of the SAM of 1 (n = 6) exhibited reversible redox of the Fe center at E_1/2 = 0.26 V (vs. Ag⁺/Ag) in the presence of Et₄NBF₄ in MeCN and at E_1/2 = 0.40 V (vs. AgCl/Ag) in the presence of NaClO₄ in H₂O. Addition of HClO₄ to the solutions shifted the redox peaks to higher potentials, E_1/2 = 0.51 V (vs. Ag⁺/Ag) in MeCN and E_1/2 = 0.48 V (vs. AgCl/Ag) in H₂O, respectively, which was ascribed to positive charge of tertiary ammonium group formed by protonation of the amino group of the azaferrocenophane. E_1/2 of SAM of 1 in H₂O solution varies depending on the anion contained in the electrolyte, NaClO₄ (0.40 V), NaBF₄ (0.46 V), Na₂SO₄ (0.53 V), and NaCl (0.55 V). Kinetic data of electron transfer between the Fe center and the gold surface of the SAM of 2-4 were obtained with variable scanning rate. Laviron’s analysis provided tunneling constant β, 0.05 Å⁻¹, suggesting that the structural changes in the SAMs on oxidation/reduction undergoes the insignificant change of the kinetic constants of the electron transfer depending on the range of the spacer length. In the acidic aqueous media, the kinetic parameters indicated that the imbalanced electron transfer between oxidized and reduced states of the Fe center was caused by the protonation of bridged amine group of azaferrocenophane.     

Simultaneous determination of vitamin K1, vitamin K1 2,3-epoxide and menaquinone-4 in human plasma by high-performance liquid chromatography with fluorimetric detection

A highly sensitive method for measuring endogenous vitamin K1, menaquinone-4 (which is one of the K2 vitamins) and vitamin K1 2,3-epoxide in human plasma was developed, based on high-performance liquid chromatography with coulometric reduction and fluorimetric detection, following extraction from plasma and purification on a Sep-Pak silica cartridge. The detection limits of vitamin K1, menaquinone-4 and vitamin K1 2,3-epoxide were 5, 5 and 8 pg per injection for the standard substances and 30, 30 and 50 pg/ml in human plasma, respectively.     

Mechanism and stereochemistry of enzymatic cyclization of 24,30-Bisnor-2,3-oxidosqualene by recombinant beta-amyrin synthase

Recombinant beta-amyrin synthase from Pisum sativum converted 24,30-bisnor-2,3-oxidosqualene into a 3:1:0.2 mixture of 29,30-bisnor-beta-amyrin, 29,30-bisnorgermanicol, and 29,30-bisnor-delta-amyrin. Further, enzyme reactions with [23-13C]- and [23,23-2H]-labeled isotopomers demonstrated that the cyclization did not proceed through formation of a lupanyl primary cation with a five-membered E-ring, but an electrophilic addition of the tetracyclic C-18 cation on to the terminal double bond directly generated a thermodynamically favored pentacyclic secondary cation with a less-strained six-membered E-ring. Interestingly, the formation of the three regioisomers suggested that the absence of the terminal methyl groups resulted in a structural perturbation in the folding conformation of the E-ring of the oleanyl cation at the active site of the enzyme.