Unexpected different chemoselectivity in the aerobic oxidation of methylated planar catechin and bent epicatechin derivatives catalysed by the Trametes villosa laccase/1-hydroxybenzotriazole system

Unreported methylated catechin and epicatechin derivatives 5 and 6 were synthesized by an oxa-Pictet- Spengler reaction. Catechin 5 shows the B and C rings coplanar because of the formation of a trans junction between the C ring and the newly generated six-term cycle D, in turn condensed to ring B. In contrast, epicatechin 6 presents a bent geometry due to the establishment of a cis junction between the C ring and the newly formed cycle D. The oxidation of compounds 5 and 6 in the presence of the Trametes villosa laccase/1-hydroxybenzotriazole (HBT) system was investigated under aerobic conditions in both a biphasic system and a reverse micelle. The unexpected different chemoselective oxidation at the benzylic position of catechin and epicatechin derivatives 5 and 6 has been rationalized using a molecular modelling approach. These results demonstrate that the Trametes villosa laccase/HBT system represents a useful tool to functionalize the C-2 or C-4 position of phenolic compounds depending on the structural features

Synthesis of a novel ester of hydroxytyrosol and lipoic acid exhibiting an antiproliferative effect on human colon cancer HT-29 cells

A novel hydroxytyrosol-lipoic acid derivative has been synthesized. Key steps are an esterification reaction between tyrosol and cJipoic acid derivatives and a regioselective aromatic hydroxylation ofthe monohydroxylated ester performed by 2-iodoxybenzoic acid (IBX) followed by an in situ reductionw ith sodium dithionite (Na2S2O4T).h e novel estere xhibited an antiproliferative effect on the human colorectal adenocarcinoma HT-29 cell line signifrcantly more potent than its parent compounds

Dimethyl carbonate: an environmentally friendly solvent for hydrogen peroxide (H2O2)/methyltrioxorhenium (CH3ReO3, MTO) catalytic oxidations

Environmentally friendly oxidations of various organic compounds with the hydrogen peroxide (H2O2)/methyltrioxorhenium(CH3ReO3, MTO) catalytic system have been described in dimethyl carbonate (DMC), a cheap commercially available and benign chemical having interesting solvating properties, low toxicity and high biodegradability. Oxidations proceeded with good conversions and in good yields. Spectrophotometric analysis demonstrated that the [CH3ReO(O–O)2] complex was formed in DMC and that it was stable for several days at room temperature.L'articolo è disponibile sul sito dell'editore: http://www.sciencedirect.co

Selected short papers from SIB-GIB 2003 Italian National Congress - Preparation and characterisation of nanostructured drug release systems

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Preparazione e caratterizzazione di sistemi micro e nanostrutturati a rilascio di farmaci

Negli ultimi anni, l'impiego di micro e nanoparticelle biodegradabili per il rilascio di farmaci è risultato un approccio importante per controllare il rilascio sia in termini di cinetica che in termini di sito-specificità. Nel presente lavoro sono state realizzate nanoparticelle di albumina e poliallilammina che sono state poi impiegate per l'intrappolamento di un antibiotico, il cefamandolo nafato. Sistemi nanostrutturati sono stati poi ottenuti per intrappolamento delle particelle ottenute in film di poliuretani. Tale strategia ha permesso di ottenere sistemi a rilascio controllato di farmaco dotati di attività antibatterica duratura nel tempo