Alessandro Bongini

Polymer-based electrochromic devices—I. Poly(3-methylthiophenes)

Abstract The basic aspects of electrochromism induced by a p-doping/undoping process of conjugated polymers are briefly described. The most important requisites for an electrochromic device are discussed, and polymer electrochromic performance data as well as the test results of a polymer-based variable light transmission electrochromic device are reported. The colour contrast control of conjugated polymers by “tailoring” their conjugation length is discussed and spectroelectrochemical data of poly(3-methylthiophenes) electrosynthesized from 3-methylthiophene isomeric dimers and isomeric tetramers are reported.

Ribavirin conjugated with lactosaminated poly-L-lysine: selective delivery to the liver and increased antiviral activity in mice with viral hepatitis.

Ribavirin (RIBV) is a useful drug in the treatment of chronic type C hepatitis but displays a toxicity for red blood cells (RBC), which limits its dosage and necessitates withdrawal in some patients. Selective concentration of RIBV in liver should improve therapeutic results. Liver targeting can be achieved by coupling the drug to galactosyl-terminating peptides, which specifically enter hepatocytes. In the present work, we conjugated RIBV to lactosaminated poly-L-lysine (L-Poly(Lys)), a hepatotropic carrier enabling intramuscular (IM) administration of conjugates. The L-Poly(Lys)-RIBV conjugate had a heavy drug load (312-327 microg of RIBV in 1 mg of conjugate) and was very soluble in 0.9% NaCl (200 mg/mL). The conjugate was devoid of acute toxicity in mouse. When incubated with human or mouse blood, it did not release the drug. After IM administration to mice, the conjugate was selectively taken up by the liver, where the drug was released in a pharmacologically active form. This was demonstrated using mice infected with a strain of murine hepatitis virus (MHV) sensitive to RIBV. Coupled RIBV, IM injected, inhibited MHV replication in liver at a daily dose two to three times lower than that of the free drug. In mice IM injected with a conjugate tritiated in the RIBV moiety, the ratios between the levels of radioactivity in liver and RBC were two times higher than in animals injected with free tritiated RIBV. In conclusion, the present results support the possibility that the chemotherapeutic index of RIBV in chronic type C hepatitis can be increased by conjugation with L-Poly(Lys).

A new synthesis of both the enantiomers of 4-amino-3-hydroxybutanoic acid (gabob) and mm2 calculations for rotamers of the intermediate oxazolidin-2-on

Abstract The easy Chromatographic separation of the diastereomertic mixture of oxazolidin-2-ones 4a and 4b allows to synthesize pure R-(-)- la and (S)-(+)-GABOB 1b . The 1H NMR pattern of 4a and 4b can be correlated with the configuration at C-5 and this relationship is confirmed by MM2 calculations for rotamera of 5-substituted oxazolidin-2-ones.

Electrochemical and optical properties of poly(3-methylthiophenes) electrosynthesized by 3,3′-, 3,4′- and 4,4′-dimethyl-2,2′-bithiophenes

Abstract The 3,3′-, 3,4′- and 4,4′-dimethyl-2,2′-bithiophenes, prepared in very pure form and characterized by 13 C NMR, were used as starting molecules for electrochemical polymerization of poly(3-methylthiophenes). The optical properties of the resulting polymers were interpreted on the basis of the conformation of the starting dimers determined by force field MMP2 calculations.

A theoretical study of the allyllithium ion-pair

Abstract Ab initio SCF computations have been performed on allyllithium using STO/3G atomic orbitals. Both the covalent and the ion-pair structures have been investigated and their energies minimized with respect to most of the geometrical parameters. The ion-pair structure is found to be more stable by 8 kcal/mol and a simple bonding scheme leads to the interpretation of its stability. The allyllithium molecule coordinated to two water molecules has also been studied to determine the effect of the solvent on the allyllithium bond.

Efficient synthesis of the four diastereomers of phosphothreonine from lactalhehyde

Abstract The four stereoisomers of phosphothreonine are obtained in high diastereomeric purity based on the stereoselective addition of trimethylsilyldiethylphosphite (TMSDEP) to scalemic N -trimethylsilyl-lacticimine and addition of TMSDEP to lactaldehyde followed by Mitsunobu inversion of the corresponding α-hydroxy-β-silyloxy phosphonate.

Trans -Diastereoselective synthesis of 3-phthalimido β-lactams via a two step-staudinger reaction

Abstract New conditions for the Staudinger reaction provide N -unsubstituted-3-phthalimido-β-lactams in satisfactory yields with complete trans-selectivity.

Push-pull amino succinimidyl ester thiophene-based fluorescent dyes: synthesis and optical characterization.

The design and synthesis of new fluorescent dyes with emission range at 490-650 nm are described. Their structural and electronic properties have been characterized by both experimental techniques and quantum-chemical calculations. The chromophores are donor-π-bridge-acceptor push-pull compounds with a π bridge of phenyl and thiophene rings and their combination. Compared with previous thiophene fluorophores, these dyes show significant redshift in the absorption and emission spectra and offer compact, red-emitting fluorophores. The dyes have amino succinimidyl active ester and can be readily conjugated to proteins, polymers and other amino-group-containing materials.

Oligothiophene S, S-dioxides : towards n-type semiconductor oligothiophenes?

Abstract A new class of thiophene based materials — oligothiophene S,S-dioxides, characterized by a much greater electron affinity than the precursor oligothiophenes — is described.

Lewis acid-catalyzed electrocyclization of 2-aza-1,3-butadienes to NH-β-lactams

Lewis acid-catalyzed cyclization of 2-aza-3-trimethylsilyloxy-buta-1,3-diene is reported. Stereochemical differences with the uncatalyzed cyclization are discussed.