Felicia D'Andrea

Biodegradation of 4-(1-nonyl)phenol by axenic cultures of the yeast Candida aquaetextoris : identification of microbial breakdown products and proposal of a possible metabolic pathway

Candida aquaetextoris, a yeast recently described for its ability to use 4-(1-nonyl)phenol (pNP) as the sole carbon and energy source in aerobic conditions, has been studied in order to determine the degradation products deriving from the growth on such a compound which is of environmental concern because of its proved toxicity to several organisms. Two main metabolites, namely trans-4-hydroxy-cinnamic acid and 4-hydroxy-acetophenone (4-acetylphenol), have been identified through either TLC and NMR spectrometry analyses of liquid substrate from cultures of C. aquaetextoris grown on pNP, with 4-acetylphenol that accumulates without any further degradation. These findings suggest that C. aquaetextoris might metabolise pNP via terminal oxidation of the alkyl chain, followed by a β-oxidation pathway. On the basis of this evidence, a novel metabolic route for the microbial degradation of 4-(1-nonyl)phenol, at least in certain yeasts, is proposed.

A SIMPLE AND HIGHLY DIASTEREOSELECTIVE PREPARATION OF GLYCAL EPOXIDES USING THE MCPBA-KF COMPLEX

Abstract Glycals are converted to the corresponding epoxides in high yields by a diastereoselective one-step epoxidation using the m -chloroperoxybenzoic acid-KF complex in anhydrous dichloromethane.

A dramatic effect of the ionic liquid structure in esterification reactions in protic ionic media

Bronsted acidic ionic liquids (ILs) have been synthesized and investigated as catalysts in esterification and transesterification reactions: simple and non-corrosive salts characterized by aliphatic cations associated with an “acidic” anion (in particular, [HSO4]−) gave the higher yields. A quite good correlation between IL acidity (H0) and catalytic ability was found although also the hydrophilic nature of the ionic medium probably affects the process efficiency.

4,6-O-BENZYLIDENE-D-GLUCOPYRANOSE AND ITS SODIUM-SALT - NEW DATA ON THEIR PREPARATION AND PROPERTIES

An improved method for the preparation of 4,6-O-benzylidene-D-glucopyranose (BG), and new or correlated data on its 1H and 13C NMR spectra, specific rotations, and tautomeric equilibria, and on those of its anomeric sodium salt (BGNa), are reported. Evidence is presented in favour of the hypothesis that crystalline BGNa exists entirely in its beta-anomeric form and that it can be useful in the access to beta-glucosides in reactions with strong electrophiles under strictly heterogeneous conditions.

Double reductive amination of l-arabino-hexos-5-uloses: A diastereoselective approach to 1-deoxy-d-galactostatin derivatives☆

Abstract The double reductive amination of l - arabino -hexos-5-ulose with benzhydrylamine and NaBH 3 CN takes place in a diastereospecific manner giving in moderate chemical yield (36 %) the galactosidase inhibitor 1-deoxy- d -galactostatin. The aminocyclization of 2,6- di -O- benzyl- l -arabino- hexos-5-ulose is more complicated giving results dependent from the type of amine: with ammonia or methylamine a mixture of C-5 epimeric 1-deoxyazapyranoses ( d -galacto l -altro ratio ≈ 4:1 ) is obtained in 45–65% combined yield, while with benzhydrylamine substantial amounts of an acyclic 1-deoxy-1-benzydrylamino-hexitol (10 % yield) is isolated together with the expected 1-deoxy-azasugars of the d - galacto and l - altro series.

'Naturalization' of textile disperse dyes through glycoconjugation: the case of a bis(2-hydroxyethyl) group containing azo dye

A family of five strictly related glycoconjugated azo dyes (GADs), characterized by the presence of the same chromophore and a variable number (1-4) of deprotected hexose units, has been prepared by employing succinate bridges for connecting the azo dye and the sugar portions. The modulation of the hydrophilic portion determines the appreciable changes in the water solubility of GADs. In all the cases, however, hydrophobic fibres (polyester) were homogeneously dyed with GADs at temperatures lower than that used for original azo dyes, at atmospheric pressure, and avoiding the use of surfactants. Furthermore, GADs show an interesting multipurpose character leading to dyeing well also the natural fibres as, for instance, wool. The presence of a variable number of hexose units in the different GADs determines some changes in the colour intensity of dyed fabrics, but in all the cases an appreciable rubbing and water fastness were maintained.

Improved preparation of 2,3:5,6:3′,4′-tri-O-isopropylidenelactose dimethyl acetal and its 6′-O-(1-methoxy-1-methylethyl) derivative

Abstract Efficient preparations both of 2,3:5,6:3′,4′-tri- O -isopropylidenelactose dimethyl acetal ( 5 , 95% yield) and its 6′- O -(1-methoxy-1-methylethyl) derivative (65% yield), useful intermediates for the conversion of lactose into biologically relevant oligosaccharides, by ‘one-pot’ acetonation procedures with 2,2-dimethoxypropane are reported. The acetonation of 5 with 2-methoxypropene in the presence of pyridinium tosylate and 4 A molecular sieves unexpectedly revealed the formation, in a first kinetic reaction phase, of similar amounts of the 2′- O - and 6′- O -(1-methoxy-1-methylethyl) acetals. The structures of all new products were fully characterized by NMR analyses, which also allowed some deductions on the conformation of the galactopyranosyl rings.

Intramolecular aldol cyclization of L-lyxo-hexos-5-ulose derivatives: a new diastereoselective synthesis of D-chiro-inositol.

Abstract The DBU-promoted intramolecular aldol condensation of two partially protected l - lyxo -hexos-5-ulose derivatives ( 8 and 9 ), in turn obtained starting from methyl β- d -galactopyranoside, takes place with fairly good yield and complete diastereoselectivity to give 2 l -(2,3,6/4,5)-pentahydroxycyclohexanone derivatives, 10 and 11 . The stereoselective reduction of inosose 10 with sodium triacetoxyborohydride leads, after catalytic debenzylation, to d - chiro -inositol ( 1 ), while the sodium borohydride reduction furnishes, with opposite stereoselectivity, a derivative of allo -inositol.

A facile conversion of 3,4-O-isopropylidene-β-d-galactopyranosides into 4-deoxy-α-l-threo-hex-4-enopyranoside and l-arabino-hexos-5-ulose derivatives

Treatment of O-protected 3,4-O-isopropylidene-β-d-galactopyranosides with tert-BuOK in N,N-dimethylformamide or methyl sulfoxide produces 4-deoxy-α-l-threo-hex-4-enopyranosides in good yields. The corresponding α-anomers and the non-O-protected derivatives are resistant to this treatment. Reaction of methyl 4-deoxy-2,6-di-O-methyl-α-l-threo-hex-4-enopyranoside with 3-chloroperbenzoic acid in CH2Cl2 gave a crystalline adduct that was hydrolyzed to 2,6-di-O-methyl-l-arabino-hexos-5-ulose.

Concise synthesis of 1-deoxy-4-O-β-d-galactopyranosyl-d-nojirimycin avoiding a glycosylation step ☆ ☆☆

Abstract 2′,6′-Di- O -benzyl-2,3:5,6:3′,4′-tri- O -isopropylidenelactose dimethyl acetal was used as starting material for the preparation of the until now unknown 4- O -β- d -galactopyranosyl- d - xylo -hexos-5-ulose derivatives 7 – 9 , through selective C-5 oxidation of its partially deprotected derivatives 4 – 6 . Hydrolysis of 7 – 9 with aq. CF 3 COOH led to deprotected 1,5-dicarbonyl disaccharides 11 – 12 , diastereoselectively transformed without purification into 1-deoxy-4- O -β- d -galactopyranosyl- d -nojirimycin derivatives in about 60% yield, through a double reductive amination reaction.