Domenico Albanese

Hindering biofilm formation with zosteric acid.

The antifoulant, zosteric acid, was synthesized using a non-patented process. Zosteric acid at 500 mg l−1 caused a reduction of bacterial (Escherichia coli, Bacillus cereus) and fungal (Aspergillus niger, Penicillium citrinum) coverage by 90% and 57%, respectively. Calculated models allowed its antifouling activity to be predicted at different concentrations. Zosteric acid counteracted the effects of some colonization-promoting factors. Bacterial and fungal wettability was not affected, but the agent increased bacterial motility by 40%. A capillary accumulation test showed that zosteric acid did not act as a chemoeffector for E. coli, but stimulated a chemotactic response. Along with enhanced swimming migration of E. coli in the presence of zosteric acid, staining showed an increased production of flagella. Reverse transcriptase-PCR revealed an increased transcriptional level of the fliC gene and isolation and quantification of flagellar proteins demonstrated a higher flagellin amount. Biofilm experiments confirmed that zosteric acid caused a significant decrease in biomass (−92%) and thickness (−54%).

Liquid–Liquid Phase Transfer Catalysis: Basic Principles and Synthetic Applications

Phase transfer catalysis (PTC) [1] was first introduced in the 1960s as a powerful tool to carry out reactions efficiently between reagents dissolved in mutually insoluble aqueous and organic phases. These reactions used to be performed by dissolving the inorganic anion in a protic organic medium, thus strongly reducing reactivity as a result of anion solvation and selectivity, as a result of solvolytic side reactions. The introduction of dipolar aprotic solvents such as dimethylformamide (DMF) or dimethylsulfoxide (DMSO) produced an enhanced reactivity by decreasing anion solvation [2]. However, their use is not devoid of drawbacks related to their cost, problematic removal, and environmental incompatibility. As a consequence of its simplicity PTC soon received widespread attention by academic and industrial chemists and is now an established procedure for many industrial applications, e.g., in the pharmaceutical and agrochemical industries, as well as in monomer synthesis and polymer modification. This chapter will focus on the basic principles of phase transfer catalysis with major attention devoted to catalysis at liquid interfaces, the topic of this book; therefore, important aspects of PTC such as solid–liquid PTC or gas–liquid PTC will only be touched on. In the last part of this chapter a restricted selection of new relevant applications of liquid–liquid PTC are also presented in order better to illustrate the scope and generality of this methodology.

Phase transfer catalysis: some recent applications in organic synthesis

Abstract A survey dealing with the use of anhydrous potassium carbonate as an efficient base for promoting organic reactions under solid–liquid phase transfer catalysis (SL-PTC) conditions is reported. In particular, the generation in situ of trifluoro- and trichloroacetamidide, and reactions of these azaanions with 2-bromocarboxylic esters and epoxides, affording protected α-amino acids and β-amido alcohols, respectively, are described. The reduction of allylic nitroderivatives with CS 2 to oximes or nitriles under SL- and liquid–liquid PTC (LL-PTC) is also presented. Finally, new preparation methods and a study of the reactivity of quaternary onium fluorides, hydrogendifluorides and dihydrogentrifluorides, together with the use of dihydrogentrifluorides as hydrofluorinating agents under SL-PTC conditions, are reported.

Regioselective conversion of O-protected glycidols to fluorohydrins catalyuzed by tetrabutylammonium dihydrogentrifluoride under solid-liquid PTC conditions

Abstract A number of O-protected glycidols are regioselectively converted into the corresponding fluorohydrins FCH2CH(OH)CH2OX by reaction with catalytic amounts of Bu4N+H2F3- and a molar excess of KHF2. Most of the protective groups (X) examined are stable under the above conditions, moreover stereogenic carbons are not affected.

Albumin as a promiscuous biocatalyst in organic synthesis

Albumin emerged as a biocatalyst in 1980 and the continuing interest in this protein is proved by numerous papers. The use of albumin was initially confined to the field of asymmetric oxidations and reductions, but more recently it has found a broader application to chemical reactions such as additions, condensations and eliminations. This review reports the main applications of albumin in organic synthesis that have appeared in the literature in the past decade.

Synthesis of N-sulfonyl aziridines through regioselective opening of epoxides under solid-liquid PTC conditions

The ring opening of epoxides 1 with 4-toluenesulfonamide (6) under solid-liquid phase transfer catalysis (SL-PTC) conditions afforded regioselectively β-sulfonamidoalcohols 7 in high yields. These were further converted into N-sulfonylaziridines 9 after activation of the hydroxy leaving group followed by ring closing in the presence of potassium carbonate.

N-Monoalkylation of α-Amino Acid Esters under Solid-Liquid PTC Conditions

N-(2-Nitrophenylsulfonyl)- (o-NBS-AA-OMe, 4) and N-(4-Nitrophenylsulfonyl)-α-amino acid methyl esters (p-NBS-AA-OMe, 5) were N-alkylated with a variety of alkyl halides 6 under solid-liquid phase-transfer catalysis (SL-PTC) conditions, affording the alkylated products o-NBS-N-R2-AA-OMe 7 and p-NBS-N-R2-AA-OMe 8 in excellent yields without any detectable racemization.

Complementary heterogeneous/homogeneous protocols for the synthesis of densely functionalized benzo[d]sultams: C-C bond formation by intramolecular nucleophilic aromatic fluorine displacement.

Polyfunctionalized benzo[d]sultams 7 and 8, which contain an alpha-amino acid unit, have been synthesized from the corresponding open chain (pentafluorobenzene)sulfonamides 4 by complementary solid-liquid phase transfer catalysis (SL-PTC) and homogeneous protocols. The cyclization step proceeds through the intramolecular nucleophilic displacement of an aromatic fluorine atom.

Cyanobacteria cause black staining of the National Museum of the American Indian Building, Washington, DC, USA

Microbial deterioration of stone is a widely recognised problem affecting monuments and buildings all over the world. In this paper, dark-coloured staining, putatively attributed to microorganisms, on areas of the National Museum of the American Indian Building, Washington, DC, USA, were studied. Observations by optical and electron microscopy of surfaces and cross sections of limestone indicated that biofilms, which penetrated up to a maximum depth of about 1 mm, were mainly composed of cyanobacteria, with the predominance of Gloeocapsa and Lyngbya. Denaturing gradient gel electrophoresis analysis revealed that the microbial community also included eukaryotic algae (Trebouxiophyceae) and fungi (Ascomycota), along with a consortium of bacteria. Energy-dispersive X-ray spectroscopy analysis showed the same elemental composition in stained and unstained areas of the samples, indicating that the discolouration was not due to abiotic chemical changes within the stone. The dark pigmentation of the stone was correlated with the high content of scytonemin, which was found in all samples.

Regioselective opening of epoxides to β-amido alcohols under solid-liquid PTC conditions

Abstract A study on the ring opening of a number of epoxides 1 with trifluoroacetamide ( 2 ) under solid-liquid phase transfer catalysis (SL-PTC) conditions has been performed. The reaction is completely regioselective affording β-amido alcohols 3 deriving from the attack of the nucleophile to the less substituted carbon atom of the oxirane ring.