Rocco Racioppi

Photochemical degradation of crude oil: Comparison between direct irradiation, photocatalysis, and photocatalysis on zeolite.

Direct irradiation for 100h of crude oil from Basilicata (Southern Italy) gave in the case of linear and branched alkanes a reduction of 9 and 5%, respectively. On the contrary, cyclic alkanes decreased for 54% while aromatic hydrocarbons showed a reduction of 37%. These results are in agreement with a prevalent electron transfer mechanism. Photocatalysis (100h) gave extensive degradation of crude oil: linear alkanes were degraded for 98.66%, branched alkanes were reduced for 97.31%, cyclic alkanes for 96.04%, while aromatic compounds and alkenes were reduced for 99.54 and 98.38%, respectively. These results are in agreement with a prevalent hydrogen abstraction mechanism. When photocatalysis is performed in the presence of zeolite linear alkanes were degraded for 79.85%, branched alkanes were reduced for 45.38%, cyclic alkanes for 58.10%, while aromatic compounds were reduced for 91.85%. In this case, an increase of the relative amount of alkenes (42.05%) was observed.

In Vitro Antifungal Activity of Burkholderia gladioli pv. agaricicola against Some Phytopathogenic Fungi

The trend to search novel microbial natural biocides has recently been increasing in order to avoid the environmental pollution from use of synthetic pesticides. Among these novel natural biocides are the bioactive secondary metabolites of Burkholderia gladioli pv. agaricicola (Bga). The aim of this study is to determine antifungal activity of Bga strains against some phytopathogenic fungi. The fungicidal tests were carried out using cultures and cell-free culture filtrates against Botrytis cinerea, Aspergillus flavus, Aspergillus niger, Penicillium digitatum, Penicillium expansum, Sclerotinia sclerotiorum and Phytophthora cactorum. Results demonstrated that all tested strains exert antifungal activity against all studied fungi by producing diffusible metabolites which are correlated with their ability to produce extracellular hydrolytic enzymes. All strains significantly reduced the growth of studied fungi and the bacterial cells were more bioactive than bacterial filtrates. All tested Bulkholderia strains produced volatile organic compounds (VOCs), which inhibited the fungal growth and reduced the growth rate of Fusarium oxysporum and Rhizoctonia solani. GC/MS analysis of VOCs emitted by strain Bga 11096 indicated the presence of a compound that was identified as 1-methyl-4-(1-methylethenyl)-cyclohexene, a liquid hydrocarbon classified as cyclic terpene. This compound could be responsible for the antifungal activity, which is also in agreement with the work of other authors.

Photochemical dimerization of esters of urocanic acid

Abstract The irradiation of urocanate esters in the presence of benzophenone in acetonitrile with a mercury lamp led to the formation of dimers. Methyl and ethyl urocanate gave a 2:1 mixture of dimethyl or diethyl c-3,t-4-di(1H-imidazol-4-yl)cyclobutane-r-l,t-2-dicarboxylate and dimethyl or diethyl t-3,c-4-di-(1H-imidazol-4-yl)cyclobutane-r-1,t-2-dicarboxylate. The allyl urocanate gave in high yields only of diallyl c-3,t-4-di(1H-imidazol-4-yl)cyclobutane-r-1,t-2-dicarboxylate. The regiochemistry of the reaction can be explained considering the frontier orbital interactions. The stereochemistry of the reaction can be justified on the basis of the ΔHf of the products. In all the cases, the most stable dimers were obtained.

Ichthyotoxic sesquiterpenes and xanthanolides from Dittrichia graveolens

Abstract The ichthyotoxicity of Dittrichia graveolens was found to be due to the major sesquiterpenes 12-carboxyeudesma-3,11(13)-diene and tomentosin. In addition, seven structurally related sesquiterpenes and two new xanthanolides were isolated and their structures elucidated.

Oxetane Synthesis through the Paternò-Büchi Reaction

The Paternò-Büchi reaction is a photochemical reaction between a carbonyl compound and an alkene to give the corresponding oxetane. In this review the mechanism of the reaction is discussed. On this basis the described use in the reaction with electron rich alkenes (enolethers, enol esters, enol silyl ethers, enanines, heterocyclic compounds has been reported. The stereochemical behavior of the reaction is particularly stressed. We pointed out the reported applications of this reaction to the synthesis of naturally occuring compounds.

The Paternò-Büchi Reaction of 2-Furylmethanols

The Paterno-Buchi reaction between 2-furylmethanol derivatives and aromatic carbonyl compounds shows good regioselectivity and high stereoselectivity. The regio- and stereoselectivity of the reaction can be explained by assuming a role of both the substituent on the 2-furylmethanol derivative and the hydroxy group in order to favor the approach of the carbonyl group towards a prochiral face of the furan. Electrochemical and kinetic properties of 2-furylmethanols are in agreement with an electron-transfer mechanism. The stereoselectivity of the reaction was confirmed using chiral 2-furylmethanols: These substrates gave the corresponding Paterno-Buchi adducts with high enantiomeric excess.

On the stereoselectivity of the Paternò-Büchi reaction between carbonyl compounds and 2-furylmethanol derivatives. The case of aliphatic aldehydes and ketones

Abstract The Paterno–Buchi reaction between 2-furylmethanol derivatives and aliphatic aldehydes and ketones induced by irradiation through Vycor at 8°C shows high regioselectivity but no stereoselectivity. This behaviour can be rationalised by assuming that this type of compound reacts through both singlet and triplet excited states. Ab initio calculations are in agreement with the formation of the 1,4-biradical. The more stable biradical accounts for the observed regioselectivity. The lack of stereoselectivity was discussed on the basis of two hypotheses. The allylic strain proposed by Adam does not account for the observed results. On the contrary, hydrogen bond interaction between (triplet excited) carbonyl oxygen and hydroxy group is able to describe the observed behaviour.

The Paterno-Buchi Reaction on Furan Derivatives

The Paterno-Buchi reaction on furan derivatives is reviewed. The photochemical reaction of furan derivatives in the reaction with carbonyl compounds gives the corresponding monoadduct with high regio- and stereoselectivity. When the reaction is carried out in benzene, a large amount of the diadduct can be obtained. The exo stereoselectivity at C-6 was explained assuming the presence of a secondary orbital effect on spin orbit coupling. Regio- and stereoselectivity of the reaction of carbonyl compounds with 2, 3-dihydrofuran is described. Applications of the reaction to the synthesis of 2- and 3-furylmethanol derivatives is reported. The synthesis of asteltoxin, avenaciolide, and oxetanocin is also reported. Asymmetric reactions on chiral glyoxylate is reported. The low diastereoselectivity of the reaction with chiral ketones and aldehydes is discussed. Finally, the high diastereoselectivity observed in the reaction with 2-furylmethanol derivatives is reported.

Enzyme-catalyzed desymmetrization of meso-skipped polyols to useful chiral building blocks

Abstract the biocatalytic desymmetrization, in presence of different enzymes, of two models of polyfunctionalized diols in a meso form was studied PFL was found to be the most selective enzyme with excellent results in chemical and optical yield with some of the tested substrates. The obtained chiral building block was utilized for some useful synthetic transformations toward the synthesis of natural products

Enzyme catalysed lactonization of 3,5 dihydroxy esters: Enantioselective synthesis of naturally occurring 3-hydroxy-5-decanolide, (−)-massoialactone, and 3-hydroxy-5-icosanolide.

Abstract Synthesis of optically active (+)-3-hydroxy-5-decanolide, (−)-massoialactone and of the recently isolated 3-hydroxy-5-icosanolide was achieved by enzyme-catalysed lactonization of racemic 3,5 dihydroxy esters with PPL in dry Et 2 O. Ees vary from 86% up to >98%.