The Gem-Tetraziridinocyclotriphosphazene Diazide,A Synthon to Monophosphazenylmonoazido Derivatives of Biological Interest

Abstract

The gem-tetraziridinocyclotriphosphazenes, N₃P₃Az₄XY, are both antitumor agents (1, 2) and immuno-modulators (3, 4) whatever X and Y are, but their selectivity for malignant cells is commonly poor. In an attempt at the production of more selective drugs, we prepared monoazido derivatives (X=N₃, Y=something else) for covalent binding to antibodies.     

Multiscale Structures to Describe Porous Media Part II: Transport Properties and Application to Test Materials

A renormalization method for the computation of the transport properties of a porous medium modelled as a multiscale random network is proposed. The method applies to electrical conduction, molecular diffusion, hydraulic transport under low Reynolds number, transport of condensable vapour, in the medium fully or partially saturated by one or two immiscible fluids. For 31 test materials, the method previously exposed by the authors for the reconstitution of the pore structure from the mercury intrusion curve is applied. Then, the intrinsic permeability is computed. The results are in good agreement with the measured permeability.     

Synthesis of Isobrassilexin,a Biologically Active Isomer of Brassilexin,a Cruciferac Phytoalexin

The synthesis of isobrassilexin 2, a hitherto non natural indoloisothiazole is reported (two steps, 43% yield). This substance, an isomer of brassilexin 1 has shown important biological properties in vitro.     

HIV-1 integrase inhibition of biscoumarin analogues

Nineteen biscoumarins bearing free and modified hydroxyl substituents at benzoyloxyphenyl linker have been synthesized by multiple step synthesis. Among these biscoumarins, thirteen were found to be active molecules against HIV-1 integrase (HIV-1 IN). The structure-activity relationship of the nineteen compounds on HIV IN may be useful for the design of potent therapeutic agents.     

Additive Properties of the Dufresne Laws and Their Multivariate Extension

The Dufresne laws are defined on the positive line by their Mellin transform , where the a _i and b _j are positive numbers, with pq, and where (x) _s denotes (x+s)/(x). Typical examples are the laws of products of independent random variables with gamma and beta distributions. They occur as the stationary distribution of certain Markov chains (X _n) on defined by where X ₀, (A ₁, B ₁),..., (A _n, B _n),... are independent. This paper gives some explicit examples of such Markov chains. One of them is surprisingly related to the golden number. While the properties of the product of two independent Dufresne random variables are trivial, we give several properties of their sum: the hypergeometric functions are the main tool here. The paper ends with an extension of these Dufresne laws to the space of positive definite matrices and to symmetric cones.     

Iodoplumbate mit polymeren Anionen – Synthese und Kristallstrukturen von [Na3(OCMe2)12][Pb4I11(OCMe2)], (Ph4P)2[Pb5I12] und (Ph4P)4[Pb15I34(dmf)6]

Iodoplumbates with Polymeric Anions – Synthesis and Crystal Structures of [Na₃(OCMe₂)₁₂][Pb₄I₁₁(OCMe₂)], (Ph₄P)₂[Pb₅I₁₂], and (Ph₄P)₄[Pb₁₅I₃₄(dmf)₆] Reactions of PbI₂ with NaI in polar organic solvents followed by crystallization with large cations yield iodoplumbate complexes with various compositions and structures. [Na₃(OCMe₂)₁₂][Pb₄I₁₁(OCMe₂)] 3 , (Ph₄P)₂[Pb₅I₁₂] 4 and (Ph₄P)₄[Pb₁₅I₃₄(dmf)₆] 7 contain one-dimensional infinite anionic chains of face- or edge-sharing PbI₆ or PbI₅L (L = acetone, DMF) octahedra. [Na₃(OCMe₂)₁₂][Pb₄I₁₁(OCMe₂)] 3 : Space group P1 (No. 1), a = 1120.3(5), b = 1265.3(6), c = 1608.3(8) pm, α = 74.64(4), β = 70.40(4), γ = 85.24(4)°, V = 2071(2) · 10⁶ pm³; (Ph₄P)₂[Pb₅I₁₂] 4 : Space group C2/c (No. 15), a = 787.00(10), b = 2812.0(5), c = 3115.9(5) pm, β = 96.240(13)°, V = 6885(2) · 10⁶ pm³; (Ph₄P)₄[Pb₁₅I₃₄(dmf)₆] 7 : Space group P2₁/n (No. 14), a = 2278.8(4), b = 1782.6(3), c = 2616.8(4) pm, β = 114.432(13)°, V = 9678(3) · 10⁶ pm³.     

Photochemistry of the three carboxypyridines in water: a pH dependent reaction

The photochemistry of ortho, meta and para-carboxypyridines (pK(a)(1)= 1.0-2.1 and pK(a)(2)= 4.7-5.3) in aqueous medium was studied by laser-flash photolysis and product studies. At pH < pK(a)(1), hydroxylated compounds are produced with low quantum yields. Within the pH range 4-7, ortho and meta isomers undergo dimerization together with decarboxylation with a quantum yield showing a very sharp maximum around pK(a)(2)([small phi](max)= 0.09 and 0.01, respectively) while the para isomer is photostable. End-of-pulse transients assigned to triplet states were detected by laser-flash photolysis at pH < pK(a)(1) and pH > 4. Additionally, the carboxypyridinyl radicals were detected as secondary intermediates at pH < pK(a)(1) and 4 < pH < 7 and the OH-adduct radicals at pH < pK(a)(1). This is in favour of an electron transfer reaction between triplet and starting compound producing a charge transfer species. The radical anion would escape as carboxypyridinyl radical while the radical cation may add water at pH < pK(a)(1) yielding the OH-adduct radical or may undergo decarboxylation at pH > 4. The high quantum yield of phototransformation of the ortho isomer at pH > 4 is due to an easy decarboxylation process. A reaction scheme is proposed accounting for the dependences of [small phi] on both the pH and the carboxypyridines concentration. This study points out the distinct pattern of reactivity of carboxypyridines depending on the ionisation state of starting compounds and isomeric substitution.     

Nondestructive monitoring of the photochromic state of dithienylethene monolayers by surface plasmon resonance

The use of surface plasmon resonance (SPR) as a nondestructive, nonerasing readout of the isomerization state of a photochromic dithienylethene covalently linked to a chemically modified gold surface was investigated. Four different binding layers were examined: 11-mercaptoundecanol (MUO), an amine-modified 11-mercaptoundecanol (MUO-NH2), dextran, and an amine-modified dextran. The binding of dithienylethene to the modified gold surface and photoisomerization of the photochrome in the bound state were established by FTIR. Solvent effects were measured for every layer tested using ethanol and hexanes. In general, large, easily measurable SPR signal changes could be detected under conditions where photoisomerization of the dithienylethene photochrome was not quenched by the gold plasmon, establishing SPR as a viable form of readout for potential dithienylethene-based optical data storage or processing devices. Dextran-bound photochrome in ethanol exhibited the largest SPR response upon photoisomerization, but is more prone to time-dependent fluctuations resulting from swelling of the dextran layer (caused by slow diffusion of the solvent) than the other layers. Large responses are also provided by MUO-NH2 and MUO, and the signal is much more stable than that for dextran.