Alessandro Medici

Use of moss (Tortula muralis Hedw.) for monitoring organic and inorganic air pollution in urban and rural sites in Northern Italy

Abstract Concentrations of polycyclic aromatic hydrocarbons (PAHs) and trace metals, as well as stable nitrogen (N) isotope composition, were determined in moss tissues from an urban area and from rural sites in northern Italy. The total PAH contents were higher in the urban area. The percentage fraction of low molecular weight volatile PAHs on total PAHs was greater in rural sites. The mean concentration ratio (urban:rural) was, overall, much lower for trace metals than for PAHs. Among metals, only Pb levels were highest in the city center, and were, in turn, associated with a more positive δ15N signature in moss tissue. This indicates that exposure to slow-moving traffic in the city center resulted both in higher Pb deposition and a greater contribution of NOx, compared with NHx, in atmospheric N pollution. Most metals (namely Cd, Cr, Fe, Ni, V and Zn) were moderately enriched in moss tissues from the urban area, especially in the sectors downwind from the main emission sources. In contrast, Co and Cu contents in the urban area did not differ from those in rural sites. We concluded that organic (PAH) and inorganic (metal) pollution showed varying patterns which reflected differences as regards both emission sources and atmospheric transport pathways. Atmospheric deposition of PAHs peaked in close vicinity to urban emission sources. Conversely, the atmospheric deposition of metals, except Pb, was more diffuse over the territory.

Biotransformations on steroid nucleus of bile acids

The bile acids in mammals are all derivatives of 5 beta-cholan-26-oic acid. They represent the major quantitative pathway by which cholesterol is metabolized in the body. This article covers the microbial and enzymatic transformations of free, saturated bile acids, that kept unaltered the C-24 cyclopentane-perhydrophenantrene nucleus. The bile acids that have been considered include the primary cholic and chenodeoxycholic acids, the secondary deoxycholic and lithocholic acids as well as the relevant dehydrocholic, ursocholic and ursodeoxycholic acids. Among the bile acid biotransformations, attention is paid to reactions that lead to pharmaceutically significant compounds. This is the case of 7 alpha-hydroxy epimerization of chenodeoxycholic acid to ursodeoxycholic acid, currently used for cholesterol galistone dissolution therapy and in the treatment of cholestatic liver diseases. Emphasis has placed on reporting reactions that may be of general interest and on the practical aspects of work in the field of biotransformations.

Anti-Prelog microbial reduction of prochiral carbonyl compounds

Abstract Yarrowia lipolytica strains isolated from various habitats were tested in the reduction of prochiral carbonyl groups. The anti-Prelog reduction ( R -enantiomer) is observed with different yields and enantiomeric excesses depending on the structure of the ketones 1a-e .

Thiazolylmethylenetriphenylphosporane and its benzo derivative: stable and practical wittig reagents for the synthesis of vinylthiazoles and vinylbenzo : two-carbon homologation of aldehydes

Abstract The title thiazolyl phosphorane is a stable yet quite reactive Wittig-type reagent which upon reaction with various aldehydes affords vinylthiazoles, mainly or exclusively as E -isomers, in very good yields. Also the benzothiazolyl phosphorane derivative, unlike a literature report, prove to react with aldehydes. Vinylthiazoles subjected to formyl deblocking from thiazole nucleous afford two-carbon homologated satured aldehydes. As an example, one of these vinylthiazoles, viz. the β-phenyl derivative 8f, proves to add n -butyl lithium cuprate to give after the formyl deblocking 3-phenylheptanal.

Plants in organic synthesis: an alternative to baker's yeast

The reduction of acetophenone 1 and the hydrolysis of 1-acetoxy-2-methylcyclohexene 3 with various commercially available plants to the corresponding S-carbinol 2 and S-ketone 4 are described. The further incubation of 2-methylcyclohexanone 4 with some plants affords the enantiomerically pure trans- and/or cis-alcohol 5 and 6, respectively.

Combined microbial oxidation and reduction: a new approach to the highyield synthesis of homochiral unsaturated secondary alcohols from racemates

Abstract The oxidation of racemic secondary alcohols with Bacillus stearothermophilus followed by reduction of the mixture with Yarrowialipolytica to afford high yields of the enantiomerically pure R-alcohols 1a, b, d is described. Comparisons with Yarrowia lipolytica reduction, Bacillus stearothermophilus oxidation, and the contemporary use of the two microrganisms have been made.

Diastereoselectivity in the 1,2-addition of silylazoles to chiral aldehydes. Stereocontrolled homologation of α-hydroxyaldehydes.

Abstract The addition of 2-trimethylsilylazoles (thiazole, benzothiazole, oxazole) to α-asymmetric aldehydes give the corresponding O -silylcarbinols in good chemical yield and high stereoselectivity; the reaction is employed for the stereoselective homologation of D -glyceraldehyde.

Kinetic resolution of racemic secondary alcohols via oxidation with Yarrowia lipolytica strains

Abstract Cyclic and alicyclic racemic secondary alcohols are kinetically resolved via oxidation with Yarrowia lipolytica strains. The comparison of the oxidation reactions with the reductions of the corresponding ketones supports the hypothesis of the presence of two alcohol dehydrogenases with opposite enantioselectivity.

Tocopherol, fatty acids and sterol distributions in wild Ecuadorian Theobroma subincanum (Sterculiaceae) seeds

Abstract Ecuadorian Theobroma subincanum (Sterculiaceae) seed parts were analyzed to determine quali-quantitative tocopherol distribution. Fatty acids and sterols in the embryos, teguments and endosperm were also evaluated with an aim to better-characterize the plant matrix for its potential use as a source of phytochemicals, for the cocoa butter processing industry and/or as a new source of low cost natural products in the cosmetic, drug and alimentary/nutraceutical industries. HPLC for tocopherols and gas-chromatography (GC), GC–mass spectrometry (MS) analyses for fatty acids profile (FAP) and phytosterols were performed. Tocopherols were particularly abundant in the embryo, with quali-quantitative data similar to wheat germ oil whereas, in the teguments and endosperm, the concentrations of tocopherols were lower. The fatty acid profile and phytosterol characterization of the seed parts showed qualitative homogeneous data. In the endosperm, 80% of the entire FAP consisted of oleic and stearic acid while, among sterols, cycloartenol was more abundant in endosperm than in embryos and teguments. Accordingly, T. subincanum seeds can be proposed as possible substitutes in the cocoa processing industry and as a potential source of vitamin E isomers.

Stereospecific homologation of d-xylo and d-galacto dialdoses by 2-trimethylsilylthiazole

Abstract Homologation of the title dialdoses is carried out by diastereogenic addition of 2-trimethylsilylthiazole (1) to the side-chain aldehyde and unmasking the formyl group from thiazole ring; further addition of 1 to the resulting homologated dialdoses exhibited good levels of diastereoselectivity.