Inclusion Complexes of Cyproterone Acetate with Cyclodextrins in Aqueous Solution

Cyproterone acetate (CPA) is a steroidal antiandrogen with a progestogenic activity. Given that this molecule has a very poor water solubility (2.1 g/mL), different cyclodextrins (CDs) were tested to form inclusion complexes and to increase solubility. Two different techniques were compared to study the affinity between CPA and CDs: phase-solubility studies and NMR spectroscopy. The stoichiometry and the stability constant could be determined for most complexes with the aid of phase-solubility studies. The greatest increase in solubility was achieved with the methylated -CDs, but hydroxypropylated - and -CDs also gave enhanced solubilities. ¹H-NMR studies showed a solubility increase similar to that found with phase-solubility studies. The proof of inclusion in the2,6-dimethyl--CD (DIMEB) was shown by ¹H-NMR and t-ROESY spectra.     

Phosphate-selective electrodes containing immobilised ionophores

Phosphate selective electrodes have been produced based upon rubbery membranes containing heterocylic macrocycles as sensors covalently bound to a cross-linked polystyrene-block–polybutadiene-block–polystyrene (SBS) polymer. The membranes were robust and the best HPO₄²⁻-selective membrane fabricated was composed of 7.1% (m/m) dicumyl peroxide, 28.3% (m/m) 2-nitrophenyloctylether, 9.8% (m/m) 3-(10-undecenyl)-1,5,8-triazacyclodecane-2,4-dione, 31.0% (m/m) SBS and 23.8% (m/m) PoleStar™ 200R (clay-based filler). The characteristics of this electrode were a linear Nernstian range of 3.9×10⁻³ to 1×10⁻⁶ mol dm⁻³ HPO₄²⁻ with a limit of detection of 1.0×10⁻⁶ mol dm⁻³ HPO₄²⁻, a slope of −29.7±0.9 mV per activity decade and a pH range from 6 to 8. Selectivity coefficients for phosphate against various interfering anions (chloride, sulfate and nitrate) were determined. Response times were 2 min or under, stability of response and electrode lifetime in continuous use were also very satisfactory. The response behavior of HPO₄²⁻-ISEs based upon mobile and bound ionophores was comparable and suggests that mobility of the ionophore is not necessary to obtain a working ISE and that covalent binding of ionophores can be used to produce ISEs of increased stability and robustness.     

Phosphines: Nucleophilic organic catalysts for the controlled ring‐opening polymerization of lactides

A new metal‐free synthetic approach to the controlled ring‐opening polymerization (ROP) of lactide with nucleophilic phosphines as transesterification catalysts is described. P(Bu)₃, PhPMe₂, Ph₂PMe, PPh₃, and related phosphines are commercially available, inexpensive catalysts that generate narrowly dispersed polylactides with predictable molecular weights. These organic catalysts must be used in combination with an initiator, such as an alcohol, to generate an alcoholate ester α‐end group upon ROP. A likely polymerization pathway is through a monomer‐activated mechanism, with minimal active species, facilitating narrow molecular weight distributions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 844–851, 2002; DOI 10.1002/pola.10168     

Highly efficient three-component synthesis of protected homoallylic amines by bismuth triflate-catalyzed allylation of aldimines

Bismuth triflate catalyzes the allylation of a variety of in situ generated protected aldimines using aldehydes, primary carbamates, and allyltrimethylsilane in a three-component reaction. The reaction proceeds rapidly and affords the corresponding protected homoallylic amine in good yield (up to 86%). Scope and limitations of the aldehyde and carbamate components are reported.     

Investigation of the Interactions of β‐Peptides with DNA Duplexes by Circular Dichroism Spectroscopy

The interaction of β‐peptides with the DNA duplexes of dA₂₀dT₂₀ and a GCN4‐binding CRE sequence was examined. To gauge the factors that govern these interactions, two β‐pentadecapeptides, 1 and 2 , a β‐dodecapeptide, 3 , three β‐decapeptides, 4 – 6 , three β‐heptapeptides, 7 – 9 , and β‐octaarginine 10 were designed and synthesized. The β‐peptides were conceived to adopt a β‐peptide 3₁₄ helix, in which the side chains at position i and i + 3 are aligned vertically along one side of the helix. The side chains of Lys, Asn, and Arg were positioned such that potential H‐bonding sites were created for a helical conformation to interact with the base pairs of DNA. CD Analysis showed that β‐peptides 1, 2 , and 10 interacted with dA₂₀dT₂₀. In addition, β‐peptides 1 and 2 showed significant interaction with a DNA‐duplex 20mer containing the ATF/CREB recognition sequence for the regulatory protein GCN4. It is impossible, at this stage of the investigation, to make a safe proposal about the actual nature of the interaction of the structures(s) of the complexes, the formation of which is suggested by the CD spectra reported herein.     

X-ray crystal structures of three nonbenzodiazepinic ligands for the benzodiazepine receptor sites: SR95926, CMW1842, and L16317:nab initio MO study of the electronic properties

The crystal structures ofp-methoxyphenyl-3-triazolo [4,3-a] isoquinoline (SR95926),p-methoxyphenyl-3-triazolophtalazine (CMW1842), andp-methoxyphenyl-3-N-dimethoxyethylamino-6-triazolophtalazine (L16317) have been solved by direct methods from single-crystal X-ray diffraction data, and refined by full-matrix least squares. SR95926: monoclinic,P2₁/n,a=20.950(3),b=6.769(1),c=9.465(2) Å,=100.90(1)°. CMW1842: triclinic,P¯1,a=8.784(1),b=9.160(4),c=8.555(1) Å,=99.10(2),=93.90(1), =106.77(1)°. L16317: monoclinic,P2₁/_n,a=20.124(3),b=9.586(1),c=10.788(1) Å,=91.91(1)°. FinalR factors are 0.034, 0.037, and 0.053, respectively. Experimental geometries were used to perform STO-3Gab initio molecular-orbital calculations. A relationship between the electronic pattern within the molecules and the affinity of the benzodiazepine receptor sites is pointed out.     

The paradox of trees in type theory

We show how to represent a paradox similar to Russell's paradox in Type Theory withW-types and a type of all types, and how to use this in order to represent a fixed-point operator in such a theory. It is still open whether such a construction is possible without theW-type.This research was partly supported by ESPIRIT Basic Research Action Logical Frameworks.     

Inégalités de Gagliardo-Nirenberg pour les semi-groupes d'opérateurs et applications

One shows the equivalence between an abstract form of a Gagliardo-Nirenberg inequality and an estimate of the decay of the L ¹–L norm of a semigroup of operators. This equivalence, contrary to the one with the classical Sobolev inequalities, allows the treatment of situations where the decay is exponential. Related results and applications are given.

Cet article a pu être terminé pendant un séjour de l'auteur à l'université d'Edimbourg.     

Rapidly decaying solutions of the nonlinear Schrödinger equation

We consider global solutions of the nonlinear Schrödinger equation

A Theoretical Study of Complex Formation between Formaldehyde and Lithium

Ab initio SCF and CI calculations on the cationic and neutral complexes of formaldehyde and lithium are reported. For the cationic complex CH₂O/Li⁺, the stabilization energy of 41.7 kcal/mol obtained from the SCF calculation increases to 51.6 kcal/mol if a configuration interaction is introduced. For the neutral complex CH₂O^?/Li⁺, the C_2v-conformer of the ²A₁-state with the equilibrium bond distances of d(C? O) = 1.23 Å and d (O? Li) = 1.90 Å is calculated to be more stable than the ₂B₁-state with d (C? O) = 1.34 Å, and d (O? Li) = 1.65 Å. Charge transfer and polarization effects upon complex formation are discussed.