Raffaele Morrone

Resolution of racemic flurbiprofen by lipase-mediated esterification in organic solvent

Abstract Resolution of rac-flurbiprofen, 2-fluoro-α-methyl-[1,1′-biphenyl]-4-acetic acid (1), by biocatalytic methodologies has been studied. Enzymatic hydrolysis of rac-flurbiprofen methyl ester (2) in aqueous-organic medium gave poor results. Transesterification of the same ester mediated by immobilized lipase from Candida antarctica (Novozym® 435) in organic solvent proceeded with good enantiomeric excess but the isolation of the product required chromatographic separation and therefore was unsuitable for large scale preparation. Direct esterification of 1 with methanol in acetonitrile promoted by Novozym® 435 proved to be the best method since it gave, via a twofold kinetic resolution, S-flurbiprofen with excellent enantiomeric excess. The R-flurbiprofen methyl ester formed in the reaction can be converted into the starting rac-flurbiprofen by alkaline hydrolysis or, alternatively, into R-flurbiprofen by hydrolysis with acid.

Enantiopure 1-hydroxymethyl-2-dimethylaminomethylferrocene as efficient catalyst in the enantioselective addition of diethylzinc to aldehydes

Abstract A ferocenyl amino atodml possessing only planar chirality has been employed as a catalyst in the enantioselective alkylation of aldehydes with Et 2 Zn. Seven chiral secondary alcohols in 64∼83% e.e. have been prepared.

Diastereoselectivity and Site Dependency in the Photochemistry of Ketoprofen in the Bovine Serum Albumin Matrix

Abstract The photodegradation of the S(+)- and R(−)-ketoprofen (KP) enantiomers in the bovine serum albumin matrix was studied by steady-state photolysis with the use of λirr > 320 nm and transient absorption spectroscopy with λexc = 355 nm, at 1/1 and 2/1 KP/BSA molar ratios. R(−)-KP was found to be more labile than S(+). Triplet ketoprofen species were evidenced with lifetimes of 400 ns for S(+) and 600 ns for R(−)-KP. Further longer-lived transients with lifetimes of 2.6 and 6.0 μs for S(+) and R(−), respectively, were detected. On the basis of the binding constants of the drug enantiomers to the two main binding sites of the protein, obtained from circular dichroism experiments, the individual disappearance quantum yields of the 1:1 and 2:1 diastereomeric KP:BSA complexes could be estimated. The photoreactivity in the BSA matrix was rationalized on the basis of diastereoselective photodecarboxylation in the two main protein sites.

Binding of a chiral drug to a protein: an investigation of the 2-(3-benzoylphenyl)propionic acid/bovine serum albumin system by circular dichroism and fluorescence

A combined approach using global analysis of circular dichroism multiwavelength data and time resolved fluorescence was applied to investigate the interaction of R-(-)- and S-(+)-ketoprofen with bovine serum albumin in buffer solution at neutral pH. A characterization of the most stable drug : protein adducts of 1 : 1 and 2 : 1 stoichiometry, as individual chemical species, was obtained. The stability constants and the absolute circular dichroism spectra of the diastereomeric complexes were determined. The spectra of the 1 : 1 conjugates are opposite in sign, those of the 2 : 1 complexes are both negative, but different in shape from each other (peaks at 358 and 342 nm for S-(+)- and R-(-)-ketoprofen, respectively). A tryptophan residue was shown to be involved in the binding of the drug, in the primary site for the R-(-) and in the secondary site for the S-(+) enantiomer, thereby showing that chiral recognition by the protein causes the site of highest affinity being not the same for both optical antipodes.

Enzyme-promoted kinetic resolution of 1-hydroxymethyl-2-dimethylaminomethylferrocene

Abstract Both enantiomers of 1-hydroxymethyl-2-dimethylaminomethylferrocene have been obtained in high enantiomeric excess by lipase-mediated irreversible acetylation using vinyl acetate as acyl donor.

Novel enzymatic recognition of the ferrocene framework: nitrile hydratase/amidase catalyzed cascade biotransformations

For the first time, two bacterial strains expressing a nitrile hydratase/amidase activity were able to recognize the ferrocene framework: Rhodococcus erythropolis A4 and Rhodococcus rhodochrous PA-34. Important parameters for the enzymatic recognition are the specific structural features of the substrates, and the inducers adopted during the bacterial growth phase.