Selective enzymatic reduction of aldehydes

Highly selective enzymatic reductions of aldehydes to the corresponding alcohols was performed using an E. coli JM109 whole cell biocatalyst. A selective enzymatic method for the reduction of aldehydes could provide an eco-compatible alternative to chemical methods. The simplicity, fairly wide scope and the very high observed chemoselectivity of this approach are its most unique features.     

Linear-quadratic optimal control under non-Markovian switching

We study a finite-dimensional continuous-time optimal control problem on finite horizon for a controlled diffusion driven by Brownian motion, in the linear-quadratic case. We admit stochastic coefficients, possibly depending on an underlying independent marked point process, so that our model is general enough to include controlled switching systems where the switching mechanism is not required to be Markovian. The problem is solved by means of a Riccati equation, which turned out to be a backward stochastic differential equation driven by the Brownian motion and by the random measure associated with the marked point process.     

XPS and AFM characterization of the enzyme glucose oxidase immobilized on SiO(2) surfaces

A process to immobilize the enzyme glucose oxidase on SiO2 surfaces for the realization of integrated microbiosensors was developed. The sample characterization was performed by monitoring, step by step, oxide activation, silanization, linker molecule (glutaraldehyde) deposition, and enzyme immobilization by means of XPS, AFM, and contact angle measurements. The control of the environment during the procedure, to prevent silane polymerization, and the use of oxide activation to obtain a uniform enzyme layer are issues of crucial importance. The correct protocol application gives a uniform layer of the linker molecule and the maximum sample surface coverage. This result is fundamental for maximizing the enzyme bonding sites on the sample surface and achieving the maximum surface coverage. Thin SiO2 layers thermally grown on a Si substrate were used. The XPS Si 2p signal of the substrate was monitored during immobilization. Such a signal is not completely shielded by the thin oxide layer and it is fully suppressed after the completion of the whole protocol. A power spectral density analysis on the AFM measurements showed the crucial role of both the oxide activation and the intermediate steps (silanization and linker molecule deposition) to obtain uniform immobilized enzyme coverage. Finally, enzymatic activity measurements confirmed the suitability of the optimized protocol.     

Development and validation of two multiresidue liquid chromatography tandem mass spectrometry methods based on a versatile extraction procedure for isolating non-steroidal anti-inflammatory drugs from bovine milk and muscle tissue

The main difficulties in analysing non-steroidal anti-inflammatory drugs (NSAIDs) in food and biological samples are due to the tight non-covalent interactions established with matrix proteins and the amount of occurring fatty material. The present paper describes an effective extraction procedure able to isolate fifteen NSAIDs (acetaminophen, salicylic acid, ibuprofen, diclofenac, flunixin and its metabolite 5-hydroxy-flunixin, nimesulide, phenylbutazone, meclofenamic acid, tolfenamic acid, meloxicam, carprofen, ketoprofen, naproxen and etodolac) from bovine milk and muscle tissue through two succeeding steps: (a) deproteinisation/extraction with organic solvent, essential to lower the medium dielectric constant and, therefore, to release the analytes from matrix; (b) SPE clean-up on OASIS cartridges. Lipids were easily removed during low-temperature centrifugations. The advantages of the developed procedure pertain to the efficient removal of the fat substances (very low matrix effect and high recovery yields) and its versatility, since it can be applied both to milk and muscle with few adjustments due to the diversity of the two matrices. Ion-pairing reversed-phase chromatography combined with the negative electrospray detection was able to achieve low detection capabilities (CCβs) for all analytes and, in particular, for diclofenac whose Maximum Residue Limit (MRL) in milk is 0.1 μg kg(-1). The methods were validated according to the guidelines of the Commission Decision 2002/657/EC and then applied for a small monitoring study. A number of samples showed traces of salicylic acid (SA), but its occurrence was not ascribed to a misuse of drugs (aspirin, salicylic acid) since SA, accumulating in plants in response to a pathogen attack, may be introduced into the food chain.     

Remarks on a Paper of M. Ochiai

This note is related to a nice short paper of M. Ochiai. We prove in a very fast way that the two-parameter family of Heegaard diagrams, constructed by Ochiai, encodes the genuine three-sphere. The result is obtained, up to isotopy, by using a sequence of only three moves in this order: a Whitehead–Zieschang reduction, a band sum and a cancellation of a handle.     

Reformatsky reactions with SmI2 in catalytic amount

A substoichiometric protocol for Reformatsky-type addition of α-haloesters, α-haloketones, α-halonitriles, and α-halophosphonates to carbonyl compounds has been developed. β-Hydroxyesters and β-hydroxynitriles were obtained in good to excellent yields.     

Synthesis of Polysubstituted Pyrrolizidines from Proline Derivatives and Conjugated Nitroolefins

The stereochemistry of 1,3-dipolar cycloaddition of azomethine ylides derived from aromatic aldehydes and i-proline alkyl esters with several nitroolefins was investigated. Cyclic and acyclic nitroolefins add to the anti form of the ylide in a highly diastereoselective but poorly regioselective manner to give pyrrolizidine derivatives. In a few cases, the stereochemical results strongly support a stepwise mechanism.     

Simultaneous deprotection–oxidation of cyclic hemiacetals: a fine ending for a Ueno–Stork ATRC to dichloro-γ-lactones

Recently we found that a copper catalysed Ueno–Stork cyclization can be a very useful means for the expedient synthesis of dichloro-γ-lactones, but, to take advantage of this step, the method still lacks of an efficient and selective follow-up. This Letter describes our progress in that field, unveiling the use of a supported and recyclable Cr^(VI) catalyst for the simultaneous deprotection and oxidation of cyclic dichloro hemiacetals.     

Condensed 2-pyrrolidinone-1,2-oxazines from lithium enolate of 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid and β-aryl, β-nitroenamines

The reaction of the lithium enolate of 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid 3 with a series of β-aryl, β-nitroenamines unexpectedly afforded 6-aryl-2-benzyl-4-oxa-1-oxo-3a-methoxycarbonyl-2,5-diazaindenes 9a-d, whose structure was determined by analytical and NMR spectroscopical analysis. The structure of 9b was further confirmed by X-ray analysis. A reasonable mechanism for their formation is given.