Ewa Żymańczyk-Duda

Accurate assay of enantiopurity of 1-hydroxy- and 2-hydroxyalkylphosphonate esters

Enantiomerically pure (Rp)-tert-butylphenylphosphinothioic acid and quinine were successfully used for the direct determination of the enantiomeric purity of diethyl 1-hydroxyalkylphosphonates. Only quinine was effective as a chiral solvating agent for the determination of the enantiomeric excess of diethyl 2-hydroxyalkylphosphonates. Copyright (C) 1996 Elsevier Science Ltd

Enantioselective reduction of diethyl 2-oxoalkylphosphonates by baker's yeast

Abstract Bakers yeast catalyses the asymmetric reductive biotransformation of diethyl 2-oxoalkylphosphonates yielding diethyl 2-hydroxyalkylphosphonates in good yields and with high enantiometric excess (>97%). As indicated by spectral analyses these hydroxyphosphonates exist in conformation which is “frozen” by intramolecular hydrogen bonding between phosphonate oxygen and hydroxyl hydrogen

Comparative study of fungal cell disruption—scope and limitations of the methods

Simple and effective protocols of cell wall disruption were elaborated for tested fungal strains: Penicillium citrinum, Aspergillus fumigatus, Rhodotorula gracilis. Several techniques of cell wall disintegration were studied, including ultrasound disintegration, homogenization in bead mill, application of chemicals of various types, and osmotic shock. The release of proteins from fungal cells and the activity of a cytosolic enzyme, glucose-6-phosphate dehydrogenase, in the crude extracts were assayed to determine and compare the efficacy of each method. The presented studies allowed adjusting the particular method to a particular strain. The mechanical methods of disintegration appeared to be the most effective for the disintegration of yeast, R. gracilis, and filamentous fungi, A. fumigatus and P. citrinum. Ultrasonication and bead milling led to obtaining fungal cell-free extracts containing high concentrations of soluble proteins and active glucose-6-phosphate dehydrogenase systems.

Biocatalytic Resolution of Enantiomeric Mixtures of 1-Aminoethanephosphonic Acid

Several fungal strains, namely Bauveria bassiana, Cuninghamella echinulata, Aspergillus fumigatus, Penicillium crustosum and Cladosporium herbarum, were used as biocatalysts to resolve racemic mixtures of 1-aminoethanephosphonic acid using L/D amino acid oxidase activity. The course of reaction was analyzed by 31P-NMR in the presence of cyclodextrin used as chiral discriminating agent. The best result (42% e.e of R-isomer) was obtained with a strain of Cuninghamella echinulata.

Application of cyanobacteria for chiral phosphonate synthesis

This is the first report on morphologically different strains of cyanobacteria: Arthrospira maxima, Nostoc cf-muscorum and Nodularia sphaerocarpa used for enantioselective bioreduction of selected, structurally different diethyl esters of oxophosphonic acids. The efficiency of the asymmetric hydrogen transfer was strongly dependent on the chemical structure of the substrates. Arthrospira maxima was active only toward diethyl (S)-2-oxopropylphosphonate (20% of yield, 99% of ee), whereas the application of Nostoc cf-muscorum as a biocatalyst allowed diethyl (S)-2-hydroxy-2-phenylethylphosphonate with a high enantiomeric excess (99%) and with 26% conversion degree to be obtained. Employing Nodularia sphaerocarpa led to the most spectacular result – diethyl (S)-2-hydroxy-2-phenylethylphosphonate with a degree of conversion of 99% and an optical purity of 92%. Enantioselective bioconversion of oxophosphonate with an aromatic side group located in the immediate vicinity of the carbonyl functionality was achieved for the first time. Additionally, flow cytometry showed excellent resistance of the cells of Nodularia sphaerocarpa against the examined xenobiotic – 2-oxo-2-phenylethylphosphonate, these cells remain viable at the concentration of 10 mM of the bioconversion substrate compared to the 1 mM described previously for a fungal biocatalyst. The effect of cultivation medium, light source and light cycle (light : dark) on the effectiveness of the biotransformation process was examined.

Application of the Beauveria bassiana strain for the enantioselective oxidation of the diethyl 1-hydroxy-1-phenylmethanephosphonate.

Biotransformation of diethyl 1-hydroxy-1-phenylmethanephosphonate using fungi Beauveria bassiana allowed resolving the racemic mixture of the substrate and due to the biocatalyst and reaction conditions modifications, leading to desired optical isomer.

Biocatalyzed Reactions in Optically Active Phosphonate Synthesis

With the dramatic growth in importance of asymmetric synthesis and application of optically pure organophosphorus compounds of defined absolute configuration, new approaches of gaining them become essential. This review is focused on representative and selected examples of recent achievements in enantioselective biotransformations of phosphoroorganic compounds.

Hydrogen bonding in diethyl 2-hydroxypropylphosphonate–an example of equilibrium between intramolecular and intermolecular bonding

The conformations of diethyl 2‐hydroxypropylphosphonate in CDCl3 were studied by means of NMR spectroscopy. This compound forms species in which intermolecular hydrogen bonding prevails in concentrated solutions whereas intramolecular bonds are predominant in dilute solutions. Usually both types of species exist in dynamic equilibrium and the formation of a certain hydrogen bond determines which of the conformers (trans or gauche) is predominant in a given solution. Copyright

Esterification of phosphonic and phosphinic acid analogues of glutamic and aspartic acids with ethyl orthoformate - Scope and limitations of the method

Abstract Reaction of C-ethyl esters of phosphonic- and phosphinic acid analogues of glutamic and aspartic acids with ethyl orthoformate provides the mixtures of N-formylamino- and N-ethoxymethyleneimino-derivatives with nearly quantitative yields. Scope and limitations of this procedure were studied by means of GC/MS technique.

Lipases and whole cell biotransformations of 2-hydroxy-2-(ethoxyphenylphosphinyl)acetic acid and its ester.

A wide spectrum of commercially available lipases and microbial whole cells catalysts were tested for biotransformations of 2-hydroxy-2-(ethoxyphenylphosphinyl)acetic acid 1 and its butyryl ester. The best results were achieved for biocatalytic hydrolysis of ester: 2-butyryloxy-2-(ethoxyphenylphosphinyl)acetic acid 2 performed by lipase from Candida cylindracea, what gave optically active products with 85% enantiomeric excess, 50% conversion degree and enantioselectivity 32.9 for one pair of enantiomers. Also enzymatic systems of Penicillium minioluteum and Fusarium oxysporum were able to hydrolyze tested compound with high enantiomeric excess (68-93% ee), enantioselectivity (44 for one pair of enantiomers) and conversion degree about 50-55%. Enzymatic acylation of hydroxyphosphinate was successful in case when porcine pancreas lipase was used. After 4days of biotransformation the conversion reaches 45% but the enantiomeric enrichment of the isomers mixture do not exceed 43%. Obtained chiral compounds are valuable derivatizing agents for spectroscopic (NMR) evaluation of enantiomeric excess for particular compounds (e.g. amino acids).