Paolo Davoli

Carotenoid pigments from the red mirror yeast, Sporobolomyces roseus

The striking reddish-pink colour of the phylloplane yeast Sporobolomyces roseus was found to be due to three major carotenoid pigments which were identified by UV and mass spectra as β-carotene, torulene and torularhodin. Simple protocols for the extraction of these pigments and their visual separation by thin-layer chromatography are presented. Ultrastructurally, the pigments were localized within numerous small lipid droplets. Putative physiological roles and the biotechnological relevance of carotenoids from red yeasts are discussed.

On the effect of ring substituents in the carbonylation of aziridines

Abstract The effect of ring substituents on the cobalt carbonyl-catalyzed carbonylation of functionalized aziridines to β-lactams has been investigated. A variety of aziridines with different substituents and stereochemistry has been synthesized and subjected to carbonylation. The ring expansion to β-lactam takes place in the absence of an electron-withdrawing substituent and higher yields are always obtained for cis-aziridines. Moreover, the regioselectivity of the reaction is affected by the nature of substituents at ring carbon atoms.

Stereoselective synthesis of fluorinated β-aminoacids from ethyl trans-N-benzyl-3-trifluoromethylaziridine-2-carboxylate

Abstract trans-N-Benzyl-3-trifluoromethyl-2-ethoxycarbonylaziridine 2a, easily obtainable in enantiopure forms by CAL-catalysed enzymatic resolution, allowed the regio- and stereoselective synthesis of chiral fluorinated anti-α-functionalised-β-aminoacids, such as trifluoroisoserinates or trifluoro-β-alanine, and trans-3-halo- or 3-hydroxy-β-lactams. Starting from the enantiomerically pure methyl analogue of the title compound, 2c, pure enantiomers of trifluoroisoserine can be obtained in high overall chemical yield. Absolute configurations of optically active β-aminoacids were determined by chemical correlation.

One-Pot Synthesis of Imidazole-4-Carboxylates by Microwave-Assisted 1,5-Electrocyclization of Azavinyl Azomethine Ylides.

Diversely functionalized imidazole-4-carboxylates were synthesized by microwave-assisted 1,5-eletrocyclization of 1,2-diaza-1,3-diene-derived azavinyl azomethine ylides. 1,2-Diaza-1,3-dienes were treated with primary aliphatic or aromatic amines and subjected to microwave irradiation in the presence of aldehydes. 3-Alkyl- and 3-arylimidazole-4-carboxylates were prepared in good yields through a one-pot multicomponent procedure. Modulation of the substituents at C-2, N-3 and C-5 was possible, and 2-unsubstituted imidazoles were obtained when paraformaldehyde was used.

(R)-(+) and (S)-(−) ethyl 4,4,4-trifluoro-3-hydroxy butanoate by enantioselective Baker’s yeast reduction

Abstract ( R )-(+) and ( S )-(−) ethyl 4,4,4-trifluoro-3-hydroxybutanoate are obtained both by enantioselective Baker’s yeast reduction of ethyl 4,4,4-trifluoro-3-oxobutanoate in the presence of allyl bromide or allyl alcohol. The two additives act as inhibitors of Si or Re yeast-enzymes, respectively.

α-Aminoester-Derived Imidazoles by 1,5-Electrocyclization of Azavinyl Azomethine Ylides

An efficient and practical method for the preparation of alpha-imidazol-1-yl esters from 1,2-diaza-1,3-dienes (DDs), alpha-amino esters, and aldehydes is described. The overall sequence features a Michael-type conjugate addition between the alpha-amino ester and the DD, followed by iminium ion formation via condensation with the aldehyde and 1,5-electrocyclization of the resulting thermally generated azavinyl azomethine ylide to afford eventually alpha-imidazol-1-yl esters. Such a protocol allows access to enantiomerically pure imidazoles from optically pure alpha-amino esters.

An unusual Xanthophyllomyces strain from leaves of Eucalyptus globulus in Chile

Xanthophyllomyces sp. was isolated as an epiphytic red yeast from leaves of Eucalyptus glo-bulus in Concepción, Chile. Sexual reproduction was by basidiospores produced from one or rarely two metabasidia arising from a yeast cell without preceding paedogamy. The main carotenoid pigment was astaxanthin. This isolate did not cluster with the X. dendrorhous complex (including Phaffia rhodozyma) in ITS and 26S rDNA-based phylogenetic analyses. The phylloplane may be a further habitat for Xanthophyllomyces, in addition to the well-known spring sap-flows of deciduous trees and the recently-characterised ascostromata of Cyttaria hariotii.

Identification and quantification of carotenoid pigments in aeciospores of the daisy rust fungus, Puccinia distincta.

The yellow-orange colour of aeciospores of the daisy rust fungus, Puccinia distincta, was found to be due to the carotenoid pigments beta,psi-carotene (gamma-carotene) and beta,beta-carotene (beta-carotene), which were identified by means of HPLC-APCI-MS. The combined concentration of beta- and gamma-carotene in the aeciospores was 3.3x10(-15) mol spore(-1) or 6 mol% mol(-1) total fatty acids. This concentration is sufficient for a postulated antioxidant role of carotenoids as free radical scavengers.

Simple method for reversed-phase high-performance liquid chromatographic analysis of fungal pigments in fruit-bodies of Boletales (Fungi)

A reversed-phase HPLC method has been developed for the analysis of hydroxylated pulvinic acid derivatives which are responsible for the pigmentation of fruit-bodies belonging to the order Boletales (Fungi). Variegatic, xerocomic and atromentic acid as well as variegatorubin were detected and separated in methanolic extracts of Boletus permagnificus and Xerocomus parasiticus, and the pigment profile of these species was compared. The identity of the pigments was confirmed by means of LC-atmospheric pressure chemical ionization (APCI) mass spectrometry.

Peer activities on Web-learning platforms--Impact on collaborative writing and usability issues

The importance of groupware tools in e-learning practice is increasing, because of their educational relevance and of the importance of group abilities in today’s job activities. The paper addresses some critical issues of asynchronous collaborative tools hosted in Web-learning platforms. A model to capture user quality perceptions for these tools is presented, and an investigation conducted in three case studies where e-learning platforms were used to share and comment on written works is reported in detail. Quantitative and qualitative data are used in a complementary way to capture the complexity of educational collaborative activities. The impact of technologies on work organization, writing and peer-feedback activities is discussed. Users dedicated more time to feedback activities than they would have in real-life contexts, and paid more attention to the style and content of their writing. Communication was more focused and honest than in real life (even though more distant and at the risk of misunderstanding), and its indirectness encouraged shy and impaired people. Usability problems emerged from platform design, educators’ choices and server-side settings; Web-based systems seem to pose specific usability issues when users are required a strong active role; compatibility issues highlight the need for a closer Web standard compliance.