Characterisation of an inclusion complex between cladribine and 2-hydroxypropyl-beta-cyclodextrin.

Parenterally administered cladribine (2-chloro-2'-deoxyadenosine) has demonstrated promising efficacy and safety in clinical trials in patients with multiple sclerosis (MS). An oral formulation of this small molecule would be an attractive option for patients. Here, we describe the chemical characterisation of the inclusion complex between cladribine and the drug carrier molecule 2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD).

A kinetic study of the conjugate addition of benzenethiol to cyclic enones catalyzed by a nonsymmetrical uranyl-salophen complex.

The Et3N-assisted addition of benzenethiol to enones in chloroform is catalyzed with high turnover efficiency by the phenyl-substituted uranyl-salophen compound 3. Catalytic data show a close adherence to a quatermolecular mechanism involving reaction of a base-activated thiol with a reversibly formed complex of enone and metal catalyst, with a complication of product inhibition due to the formation of a product-catalyst complex. The role of the binding energy made available by interactions with the aromatic sidearm of the catalyst is discussed in terms of catalyst-substrate and catalyst-transition state complementarity.

Rhodium-mediated stereoselective polymerization of "carbenes".

Unprecedented rhodium-catalyzed stereoselective polymerization of "carbenes" from ethyl diazoacetate (EDA) to give high molecular mass poly(ethyl 2-ylidene-acetate) is described. The mononuclear, neutral [(N,O-ligand)M(I)(cod)] (M = Rh, Ir) catalytic precursors for this reaction are characterized by (among others) single-crystal X-ray diffraction. These species mediate formation of a new type of polymers from EDA: carbon-chain polymers functionalized with a polar substituent at each carbon of the polymer backbone.

"Oscillating" metallocene catalysts: what stops the oscillation?

The 150 MHz (13)C NMR microstructural analysis of polypropylene samples produced with two representative "oscillating" metallocene catalysts of largely different steric hindrance, namely [(2-(3,5-di-tert-butyl-4-methoxyphenyl)indenyl)(2)ZrP](+) and [(2-phenylindenyl)(2)ZrP](+) (P = polymeryl), and the implications on the origin of the stereocontrol are presented and discussed in detail. The original mechanistic proposal of an "oscillation" between a rac-like (isotactic-selective) and a meso-like (nonstereoselective) conformation cannot explain the observed polymer configuration. The isotactic-stereoblock nature of the polymers obtained with the former catalyst proves unambiguously that the active cation "oscillates" between the two enantiomorphous rac-like conformations at an average frequency that, even at high propene concentration, is only slightly lower than that of monomer insertion.

A new syringopeptin produced by bean strains of Pseudomonas syringae pv. syringae.

Two strains (B728a and Y37) of the phytopathogenic bacterium Pseudomonas syringae pv. syringae isolated from bean (Phaseolus vulgaris) plants were shown to produce in culture both syringomycin, a lipodepsinonapeptide secreted by the majority of the strains of the bacterium, and a new form of syringopeptin, SP(22)Phv. The structure of the latter metabolite was elucidated by the combined use of mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy and chemical procedures.

Rates and Equilibria of the Michael-Type Addition of Benzenethiol to 2-Cyclopenten-1-ones.

The triethylamine-catalyzed addition reactions of benzenethiol to 2-cyclopenten-1-one and its 2- and 3-methyl derivatives have been found to be appreciably reversible in chloroform solution. Rates and equilibria have been carefully measured at 25 degrees C in order to assess the negative influence on addition exerted by methyl groups substituted on the carbon-carbon double bond. 2-Methyl-2-cyclopenten-1-one has been found to react with benzenethiol under kinetic control to give the cis adduct as the sole detectable product in a highly stereoselective anti addition process.

Effect of Cation-Complexing Agents on the Ba(II)-Assisted Basic Ethanolysis of Phenyl Acetate: From Cation Deactivation to Cation Activation.

A thorough investigation of the effect of adding cation complexing agents on the barium-assisted basic ethanolysis of phenyl acetate shows that any catalytic activity disappears upon sequestration of the metal ion by cryptand 222, but addition of the crown ethers 18C6, 15C5, and 12C4 yields ternary complexes of 1:1:1 (crown ether)-(metal ion)-ethoxide composition, in which instead of the expected cation deactivation a definite cation activation takes place. Clear-cut evidence was obtained that the quaternary complex [EtOBa(15C5)(2)](+), albeit substantially less reactive than the uncomplexed barium-bound ethoxide, is still more reactive than free ethoxide.