Aldo Bosetti

Enzymatic resolution of 1,2-diols: preparation of optically pure dropropizine

Abstract Kinetic resolution of (R,S)-3-(4-phenyl-1-piperazinyl)-1,2-propanediol diacetate ( 2 ) by alcoholysis with n -propanol was carried out under lipase Amano PS catalysis in various organic solvents. Pure enantiomers of the corresponding diol ( 1 ) are useful as antitussive and central sedative therapeutic agents.

Characterization of Bio‐oil from Hydrothermal Liquefaction of Organic Waste by NMR Spectroscopy and FTICR Mass Spectrometry

Solid wastes of organic origins are potential feedstocks for the production of liquid biofuels, which could be suitable alternatives to fossil fuels for the transport and heating sectors, as well as for industrial use. By hydrothermal liquefaction, the wet biomass is partially transformed into a water-immiscible, oil-like organic matter called bio-oil. In this study, an integrated NMR spectroscopy/mass spectrometry approach has been developed for the characterization of the hydrothermal liquefaction of bio-oil at the molecular level. (1)H and (13)C NMR spectroscopy were used for the identification of functional groups and gauging the aromatic carbon content in the mixture. GC-MS analysis revealed that the volatile fraction was rich in fatty acids, as well as in amides and esters. High-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) has been applied in a systematic way to fully categorize the bio-oil in terms of different classes of components, according to their molecular formulas. Most importantly, for the first time, by using this technique, and for the liquefaction bio-oil characterization in particular, FT-MS data have been used to develop a methodology for the determination of the aromatic versus aliphatic carbon and nitrogen content. It is well known that, because they resist hydrogenation and represent sources of polluting species, both aromatic molecules and nitrogen-containing species raise concerns for subsequent upgrading of bio-oil into a diesel-like fuel.

Bioconversion of substituted naphthalenes to the corresponding 1,2-dihydro-1,2-dihydroxy derivatives. Determination of the regio- and stereochemistry of the oxidation reactions

A mutant (TTC1) derived from Pseudomonas fluorescens N3 has been obtained for use in the bioconversion of several naphthalene derivatives to the corresponding optically active cis-dihydrodiols on a milligrams-to-grams scale. All main compounds have been characterized, their relative and absolute configuration assigned, and their enantiomeric purity determined. The regio- and stereoselectivity of the transformation has been established. The procedure therefore represents a valid method for the convenient preparation of a pool of valuable chiral syntons and auxiliaries.

Effects of chemical modification on stereoselectivity of Pseudomonas cepacia lipase

Abstract Two chemically modified forms of lipase from Pseudomonas cepacia were prepared by acylation of the free amino groups of the protein with acetic and succinic anhydrides. The catalytic activity, the enantioselectivity and the thermal stability of the modified enzymes were compared with that of the native form. Succinylation determined an increase of stability without affecting the catalytical properties of the enzyme in the hydrolysis of chiral esters. Acetylation resulted in an enhanced catalytic activity coupled to a decreased stereoselectivity and thermal stability.

STEREOSELECTIVE MICROBIAL HYDROLYSIS OF 2-ARYLOXYPROPIONITRILES

Abstract2-Aryloxypropionic acids 3a–f, compounds with herbicidal activity, have been prepared with high enantiomeric purity by microbial hydrolysis of the corresponding racemic nitriles and amides in presence ofBrevibacteriumimperiale cells.

Microbial oxidation of naphthalene to cis-1,2-dihydroxy-1,2-dihydronaphthalene in a membrane bioreactor

A microbial dihydroxylation process for the production of cis-1,2-dihydroxy-1,2-dihydronaphthalene from naphthalene is reported. The oxidation reaction was initially studied in a stirred tank reactor using resting cells of a Pseudomonas fluorescens mutant, grown on glucose as carbon source and acetyl salicylate as inducer of the naphthalene dioxygenase enzymatic system. In these conditions the productivity of the system was limited by the efficiency of the oxygenation and by a reversible product inhibition phenomenon. In order to overcome the inhibitory effect of the 1,2-dihydrodiol accumulation, the biotransformations were carried out in a stirred reactor equipped with a membrane ultrafiltration device. In this way, the cells and the insoluble naphthalene were retained and recycled into the vessel, while the soluble diol was continuously removed through the membrane permeate. The diol was recovered by selective adsorption on a column packed with an adsorbent resin, allowing the rapid and direct recycle of the reaction medium back to the enzymatic reactor. This system afforded a final yield three-fold higher than that of the batch process, exhibiting a bioconversion rate of 1.3 g h -1 dm -3 for more than 16 h of continuous working.

Oxidation of polycyclic aromatic heterocycles by Pseudomonas fluorescens TTC1

Abstract The mutant strain Pseudomonas fluorescens TTC1 (NCIMB 40605), derived from the naphthalene-degrading P. fluorescens N3 (NCIMB 40530), was used for the biotransformation of polycyclic aromatic heterocycles such as dibenzothiophene, dibenzofuran, thianthrene xanthen and acridine. The cis-1,2- and cis-3,4-dihydrodiols produced were isolated and identified from the culture filtrate. Both the regioselectivity and the productivity of the transformations, catalysed by the naphthalene dioxygenase enzymatic system, were dramatically influenced by the presence of the heteroatom. The high substrate tolerance displayed by the enzyme might be useful in the biotransformation of other related compounds.

RESOLUTION OF ISOPROPYLIDENE-GLYCEROL BENZOATE BY SEQUENTIAL ENZYMATIC HYDROLYSIS AND PREFERENTIAL CRYSTALLIZATION

Abstract Both enantiomers of isopropylidene-glycerol are prepared from its benzoate ester with enantiomeric excess ≥95% by combined partially stereoselective lipasecatalyzed hydrolysis and preferential crystallization.

Lipase-Catalyzed Resolution of Isopropylidene Glycerol: Effect of Co-Solvents on Enantioselectivity

The resolution of 1,2-O-isopropylidene glycerol via enzyme catalyzed hydrolysis of the corresponding benzoic ester was investigated. Using lipase PS from Pseudomonas cepacia, we determined the influence of organic co-solvents on the activity and enantioselectivity of the enzyme. The performance of the lipase was correlated to the nature (logP, ϵ,μ and the percentage of the organic media. The highest enzymatic activity was found in solvents completely miscible or completely immiscible in water. The enzyme stereoselectivity was inversely related to the logP of the solvent.

Enzymatic resolution of 1,2-diols: comparison between hydrolysis and transesterification reactions

A new practical procedure for the enzymatic resolution of 1,2-diols 1a–e has been developed by lipase-catalysed regio- and enantio-selective esterification using anhydrides as acylating agents in organic solvents.