Isolation,Purification and Characterisation of an Organic Solvent-Tolerant Ca2+-Dependent Protease from Bacillus megaterium AU02

A new organic solvent-tolerant strain Bacillus megaterium AU02 which secretes an organic solvent-tolerant protease was isolated from milk industry waste. Statistical methods were employed to achieve optimum protease production of 43.6 U/ml in shake flask cultures. The productivity of the protease was increased to 53 U/ml when cultivated under controlled conditions in a 7-L fermentor. The protease was purified to homogeneity by a three-step process with 24 % yield and specific activity of 5,375 U/mg. The molecular mass of the protease was found to be 59 kDa. The enzyme was active over a wide range of pH (6.0–9.0), with an optimum activity at pH 7.0 and temperature from 40 to 70 °C having an optimum activity at 50 °C. The thermal stability of the enzyme increased significantly in the presence of CaCl₂, and it retained 90 % activity at 50 °C for 3 h. The K _m and V _max values were determined as 0.722 mg/ml and 0.018 U/mg respectively. The metalloprotease exhibited significant stability in the presence of organic solvents with log P values more than 2.5, nonionic detergents and oxidising agent. An attempt was made to test the synthesis of aspartame precursor (Cbz-Asp-Phe-NH₂) which was catalysed by AU02 protease in the presence of 50 % DMSO. These properties of AU02 protease make it an ideal choice for enzymatic peptide synthesis in organic media.     

Isolation,Purification and Characterization of a Surfactants-, Laundry Detergents- and Organic Solvents-Resistant Alkaline Protease from <Emphasis Type="Italic">Bacillus</Emphasis> sp. HR-08

Bacillus sp. HR-08 screened from soil samples of Iran, is capable of producing proteolytic enzymes. 16S rDNA analysis showed that this strain is closely related to Bacillus subtilis, Bacillus licheniformis, Bacillus pumilus, Bacillus mojavensis, and Bacillus atrophaeus. The zymogram analysis of the crude extract revealed the presence of five extracellular proteases. One of the proteases was purified in three steps procedure involving ammonium sulfate precipitation, DEAE-Sepharose ionic exchange and Sephacryl S-200 gel filtration chromatography. The molecular mass of the enzyme on SDS-PAGE was estimated to be 29 kDa. The protease exhibited maximum activity at pH 10.0 and 60 °C and was inhibited by PMSF but it was not affected by cysteine inhibitors, suggesting that the enzyme is a serine alkaline protease. Irreversible thermoinactivation of enzyme was examined at 50, 60, and 70 °C in the presence of 10 mM CaCl₂. Results showed that the protease activity retains more than 80% and 50% of its initial activity after incubation for 30 min at 60 and 70 °C, respectively. This enzyme had good stability in the presence of H₂O₂, nonionic surfactant, and local detergents and its activity was enhanced in the presence of 20% of dimethyl sulfoxide (DMSO), dimethyl formamide (DMF) and isopropanol. The enzyme retained more than 90% of its initial activity after pre-incubation 1 h at room temperature in the presence of 20% of these solvents. Also, activation can be seen for the enzyme at high concentration (50%, v/v) of DMF and DMSO.     

An Oxidant- and Solvent-Stable Protease Produced by <Emphasis Type="Italic">Bacillus cereus</Emphasis> SV1: Application in the Deproteinization of Shrimp Wastes and as a Laundry Detergent Additive

The current increase in amount of shrimp wastes produced by the shrimp industry has led to the need in finding new methods for shrimp wastes disposal. In this study, an extracellular organic solvent- and oxidant-stable metalloprotease was produced by Bacillus cereus SV1. Maximum protease activity (5,900 U/mL) was obtained when the strain was grown in medium containing 40 g/L shrimp wastes powder as a sole carbon source. The optimum pH, optimum temperature, pH stability, and thermal stability of the crude enzyme preparation were pH 8.0, 60 °C, pH 6–9.5, and <55 °C, respectively. The crude protease was extremely stable toward several organic solvents. No loss of activity was observed even after 60 days of incubation at 30 °C in the presence of 50% (v/v) dimethyl sulfoxide and ethyl ether; the enzyme retained more than 70% of its original activity in the presence of ethanol and N,N-dimethylformamide. The protease showed high stability toward anionic (SDS) and non-ionic (Tween 80, Tween 20, and Triton X-100) surfactants. Interestingly, the activity of the enzyme was significantly enhanced by oxidizing agents. In addition, the enzyme showed excellent compatibility with some commercial liquid detergents. The protease of B. cereus SV1, produced under the optimal culture conditions, was tested for shrimp waste deproteinization in the preparation of chitin. The protein removal with a ratio E/S of 20 was about 88%. The novelties of the SV1 protease include its high stability to organic solvents and surfactants. These unique properties make it an ideal choice for application in detergent formulations and enzymatic peptide synthesis. In addition, the enzyme may find potential applications in the deproteinization of shrimp wastes to produce chitin.     

Inactivation Kinetics of Polyphenol Oxidase from Pupae of Blowfly (Sarcophaga bullata) in the Dimethyl Sulfoxide Solution

The effects of dimethyl sulfoxide (DMSO) on the activity of polyphenol oxidase (PPO, EC 1.14.18.1) from blowfly pupae for the oxidation of l-3,4-dihydroxyphenylalanine were studied. The results showed that low concentrations of DMSO could lead to reversible inactivation to the enzyme. The IC₅₀ value, the inactivator concentration leading to 50% activity lost, was estimated to be 2.35 M. Inactivation of the enzyme by DMSO was classified as mixed type. The kinetics of inactivation of PPO from blowfly pupae in the low concentrations of DMSO solution was studied using the kinetic method of the substrate reaction. The rate constants of inactivation were determined. The results show that k ₊₀ was much larger than k _{+ 0}￠ k_{ + 0}^\prime , indicating that the free enzyme molecule was more fragile than the enzyme–substrate complex in the DMSO solution. It was suggested that the presence of the substrate offers marked protection of this enzyme against inactivation by DMSO.     

Inhibition Kinetics of Cabbage Butterfly (<Emphasis Type="Italic">Pieris rapae</Emphasis> L.) Larvae Phenoloxidase Activity by 3-Hydroxy-4-Methoxybenzaldehyde Thiosemicarbazone

Phenoloxidase (PO) is a key enzyme in insect development, responsible for catalyzing the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones. In the present study, the kinetic assay in air-saturated solutions and the kinetic behavior of PO from Pieris rapae (Lepidoptera) larvae in the oxidation of l-tyrosine (a monophenol) and l-DOPA (l-3, 4-dihydroxyphenylalanine) (a diphenol) was studied. The inhibitory effects of 3-hydroxy-4-methoxybenzaldehyde thiosemicarbazone (3-H-4-MBT) on the monophenolase and diphenolase activities of PO were also studied. The results show that 3-H-4-MBT can inhibit both the monophenolase and diphenolase activities of PO. The lag period of l-tyrosine oxidation catalyzed by the enzyme was obviously lengthened and the steady-state activities of the enzyme sharply decreased. The inhibitor was found to be noncompetitively reversible with a K _I (K _I = K _IS) of 0.30 μmol/L and an estimated IC₅₀ of 0.14 ± 0.02 μmol/L for monophenolase and 0.26 ± 0.04 μmol/L for diphenolase. In the time course of the oxidation of l-DOPA catalyzed by the enzyme in the presence of different concentrations of 3-H-4-MBT, the rate decreased with increasing time until a straight line was approached. The microscopic rate constants for the reaction of 3-H-4-MBT with the enzyme were determined.     

A Selective HIV‐Protease Assay Based on a Chromogenic Amino Acid

(2S,3S)‐2‐Amino‐3‐hydroxy‐5‐(4‐nitrophenoxy)pentanoic acid ( 5 ) was prepared stereoselectively as the N‐Fmoc, O‐(tert‐butyl)‐protected derivative 5a in eleven steps from ethyl (E)‐4‐benzyloxypent‐2‐enoate ( 6 ). This protected amino acid was used for the solid‐phase peptide synthesis of oligopeptides, which serve as sequence‐specific chromogenic protease substrates when used in the presence of NaIO₄ and bovine serum albumin. The peptide 1 (KRAVNle 5  EANleNH₂ (Nle=norleucine)) allows detection of HIV‐protease activity spectrophotometrically at 405 nm.     

Polytetrahydrofuran amphiphilic networks. IV. Swelling behavior of poly(acrylic acid)‐l‐polytetrahydrofuran and poly(methacrylic acid)‐l‐polytetrahydrofuran networks

Poly(acrylic acid)‐l‐polytetrahydrofuran (PAA‐l‐PTHF) and poly(methacrylic acid)‐l‐polytetrahydrofuran (PMAA‐l‐PTHF) networks were synthesized by the free‐radical copolymerization of hydrophobic polytetrahydrofuran diacrylates with hydrophilic acrylic acid and methacrylic acid. Their swelling behavior was studied. Both PAA‐l‐PTHF and PMAA‐l‐PTHF networks had four solubility parameters, which indicated that they exhibited not only the properties of both hydrophobic and hydrophilic segments but also the combined properties of these two segments. The swell of these two series of networks was composition‐dependent in organic solvents and water. The relationship between the equilibrium swelling ratio (SR_e) in nonpolar solvents and the composition of the networks [the weight fraction of the PTHF segment (PTHF%)] may be expressed with a linear equation: SR_e = A × PTHF% + B. A and B are parameters that relate to the interaction of hydrophilic and hydrophobic segments with nonpolar solvents and to the properties of the networks, respectively. Because of the presence of a ? COOH group, these two network series were pH‐sensitive when the content of hydrophilic segments was higher. The pH sensitivity of networks could be controlled not only by the composition of the networks but also by the hydrophobic degree of the hydrophilic segments. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1784–1790, 2001     

Characterization of a Novel Organic Solvent Tolerant Protease from a Moderately Halophilic Bacterium and Its Behavior in Ionic Liquids

An extracellular protease was purified from a novel moderately halophilic bacterium Salinivibrio sp. strain MS-7 by the combination of an acetone precipitation (40–80 %) step and a DEAE-cellulose anion exchange column chromatography. Kinetic parameters of the enzyme exhibited V _max and K _m of 130 U/mg and 1.14 mg/ml, respectively, using casein as a substrate. The biochemical properties of the enzyme revealed that the 21-kDa protease had a temperature and pH optimum of 50 °C and 8.0, respectively. The enzyme was strongly inhibited by phenylmethylsulfonyl fluoride, Pefabloc SC, chymostatin, and also EDTA, indicating that it belongs to the class of serine metalloproteases. Interestingly, Ba²⁺ and Ca²⁺ (2 mM) strongly enhanced the enzyme activity, while Fe²⁺ and Mg²⁺ activated moderately and Zn²⁺, Ni²⁺, and Hg²⁺ decreased the enzyme activity. The effect of organic solvents with different logP on the purified protease revealed complete stability in toluene, ethyl acetate, chloroform, and n-hexane at 10 and 50 % (v/v) and moderate stability even in 50 % of DMSO and ethanol. The behavior of the MS-7 protease in three imidazolium-based ionic liquids exhibited suitable activity in these green solvent systems, especially in 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]). Comparison of the purified protease with other previously reported proteases suggests that strain MS-7 secrets a novel organic solvent-tolerant protease with outstanding activity in organic solvents and imidazolium-based ionic liquids, which could be applied in low water synthetic section of industrial biotechnology.     

Enthalpy characteristics of dissolution of <Emphasis Type="SmallCaps">l</Emphasis>-cysteine and <Emphasis Type="SmallCaps">l</Emphasis>-asparagine in aqueous solutions of acetonitrile and dimethyl sulfoxide at 298.15 K

The integral enthalpies of dissolution Δ_sol H ^m of l-cysteine and l-asparagine in mixtures of water with acetonitrile and dimethyl sulfoxide at the concentration of organic solvent up to 0.32 molar fractions were measured by means of dissolution calorimetry. The standard enthalpies of dissolution (Δ_sol H°) and transfer (Δ_trans H°) of the amino acids from water to a mixed solvent were calculated. The enthalpy coefficients of pair interactions for L-cysteine and L-asparagine with cosolvent molecules are positive, except for the L-asparagine-water-acetonitrile system. The concepts on the prevailing effect of specific interactions in solutions and the influence of the nature of the cosolvents and lateral substituents of the amino acids on the thermochemical characteristics of dissolution were used to explain the data obtained.     

Analysis of multicomponent mixture and simultaneous enantioresolution of proteinogenic and non-proteinogenic amino acids by reversed-phase high-performance liquid chromatography using chiral variants of Sanger’s reagent

Four chiral derivatizing reagents (CDR 1–4), namely, FDNP-l-Ala, FDNP-l-Val, FDNP-l-Phe, and FDNP-l-Leu, were synthesized using microwave (MW) irradiation by substituting one of the fluorine atoms in difluoro dinitro benzene (DFDNB) with l-Ala, l-Val, l-Phe, and l-Leu (CDR 1–4). The other set of CDRs, namely, FDNP-l-Phe-NH₂, FDNP-l-Val-NH₂, and FDNP-l-Leu-NH₂, was also prepared. These reagents were used for synthesis of diastereomers of 18 proteinogenic and 08 non-proteinogenic amino acids, which were resolved by reversed-phase high-performance liquid chromatography using C18 column and gradient eluting mixture of aq.TFA and acetonitrile with UV detection at 340 nm. The reagents were used for resolution of a complex mixture of 18 racemic proteinogenic amino acids in a single chromatographic run of 65 min and to determine concentration of the d-amino acid in a solution of dl-amino acid. The resolution (R _S) and selectivity (α) obtained for the two sets of diastereomers were compared among themselves and among the two groups. The method was validated for accuracy, precision, limit of detection (LOD), and limit of quantification. LOD is 0.001% impurity of d-enantiomer.     

Temperature- and pressure-responsive properties of <Emphasis Type="SmallCaps">l</Emphasis>- and<Emphasis Type="SmallCaps"> dl</Emphasis>-forms of poly(<Emphasis Type="Italic">N</Emphasis>-(1-hydroxymethyl)propylmethacrylamide) in aqueous solutions

The structural transition of the l- and dl forms of poly(N-(1- hydroxymethyl)propylmethacrylamide (PHMPMA) in aqueous solution was studied by measuring the pressure dependence of the apparent scattering intensity, differential scanning calorimetry (DSC), and circular dichroism (CD). The thermodynamic implications of the results are discussed in relation to the chiral structure of the side chain, and differences in the thermal and barometric transitions. T-P diagrams of the transition showed characteristic ellipsoid features. Antagonism of the temperature and pressure effects was observed only for P(dl-HMPMA). For P(l-HMPMA), the transition temperature (T _tr) decreased with increasing pressure, and the highest T _tr was observed at atmospheric pressure (0.1 MPa). For both polymers, the highest P _trs were observed at the lowest temperatures. The l polymer showed a specific negative peak in its CD spectrum at around 220 nm in the lower temperature region and the temperature dependence was reproduced by a single-step transition, with the midpoint corresponding to the T _tr obtained from the scattering measurements. Coupled with the results from the DSC, the different behavior between the P(l-HMPMA) and P(dl-HMPMA) could be explained in terms of the chain states before and after the transition. The cooperative factors derived from the DSC measurement revealed that about 4 to 5 polymers of the present size were necessary to perform a thermal transition for P(l-HMPMA), and that P(dl-HMPMA) underwent its transition as an almost single molecular event.This revised version was published online in June 2005 with correction to the article category.     

Characterization of a Recombinant Thermostable Dehalogenase Isolated from the Hot Spring Thermophile <Emphasis Type="Italic">Sulfolobus tokodaii</Emphasis>

A putative dehalogenase, l-HAD_ST, from the thermophile Sulfolobus tokodaii, was cloned and expressed in Escherichia coli. The recombinant enzyme catalyzes the stereospecific dehalogenation of l-2-haloacids with similar levels of activity as its homolog from mesophiles. l-HAD_ST remains fully active after being incubated for 4 h at 70 °C and tolerates extreme pH conditions ranging from 4 to 10. Furthermore, it can be purified conveniently without the usage of any chromatography method. The high expression yield and easy purification procedure make the recombinant dehalogenase an excellent candidate for biotechnological applications.     

Morphological Changes Induced by Addition of Polystyrene to Dextran-Polystyrene Block Copolymer Solutions

Summary: In this work we discuss the self-assembling behaviour in solution of a block copolymer, dextran-block-polystyrene, in the presence of homopolystyrene (PS) which allows to decrease the hydrophilic fraction f of the mixture. Dynamic and static light scattering experiments have been carried out in water-miscible solvents (DMSO and THF) to probe the formation of supramolecular structures. Results have been compared to those obtained with a block copolymer solution having the same hydrophilic fraction f. Interestingly, the morphology of the self-assembled structures was the same for a given value of f.     

Optical enzyme sensor for determining <Emphasis Type="SmallCaps">l</Emphasis>-lysine content using <Emphasis Type="SmallCaps">l</Emphasis>-lysine oxidase from the rockfish <Emphasis Type="BoldItalic">Sebastes schlegeli</Emphasis>

l-Lysine (l-Lys) in living bodies is critical for metabolism; therefore, determination of its levels in food is important. Most enzymatic methods for l-Lys analysis are performed using l-lysine oxidase (LyOx), but commercially manufactured LyOx is generally not highly selective for l-Lys among amino acids. We previously isolated LyOx as an antibacterial protein secreted from the skin of the rockfish Sebastes schlegeli. In the present study, we developed an optical enzyme sensor system for rapid and continuous determination of l-Lys using this LyOx. The system comprised an immobilized LyOx membrane, an optical oxygen probe, a flow system, and a personal computer. The amount of l-Lys was detected as a decrease in the oxygen concentration due to the LyOx reaction. The specificity of the sensor was examined against various amino acids. The sensor response was specific for l-Lys. Good reproducibility was obtained in 58 assays. The response of the sensor using commercially prepared LyOx was unstable compared with the response using LyOx isolated in our laboratory. Our sensor system could be used for 5 weeks without our having to change the enzyme membrane. The calibration curve for a standard l-Lys solution was linear from 0.1 to 3.0 mmol L⁻¹. One assay could be completed within 2 min. The sensor was applied to determine the l-Lys content in food samples such as bonito cooking water and scallop hepatopancreas. The values obtained using the sensor and conventional high-performance liquid chromatography methods were well correlated.     

Electrochemical study of gallium(III) with <Emphasis Type="SmallCaps">l</Emphasis>-glutamine at the dropping mercury electrode

Abstract  

Gallium complexes of l-glutamine have been studied polarographically in aqueous media. The reduction was found to be irreversible and diffusion controlled in the presence of 0.1 M KNO₃ and 0.002% Triton-x-100. The values of kinetic parameters, transfer coefficient (α _n), and formal rate constant ( k_{\textf,\texth}⁰ k_{{{\text{f}},{\text{h}}}}^{0} ) of the electrode reactions were calculated by Koutecky's method. The stability constants and composition of the gallium(III)-l-glutamine complexes were evaluated with the help of the Deford-Hume method. The values of stability constants of 1:1, 1:2, and 1:3 gallium(III)-l-glutamine complexes are 1.35, 6.5, and 1,350 at 30 °C, respectively. The values of thermodynamic parameters, the free energy of activation, the enthalpy of activation, and the entropy of activation have been determined at 30 °C. The formation of the metal complexes has been found to be non-spontaneous, endothermic in nature, and entropically favorable at higher temperature.     

Solvent extraction studies on tetravalent selenium

A systematic study has been carried out on the extraction of SeI₄, by various water-immiscible organic solvents. Extraction has been investigated as a function of H₂SO₄ and Kl concentrations. It has been found that Se(IV) extraction is appreciably increased by addition of iodide ion to sulfuric acid solutions. On the other hand, the presence of water-miscible alcohols and acetone was found to enhance Se(IV) extraction from H₂SO₄–Kl solutions. In the light of the results, an extraction mechanism is suggested.     

Enantiomeric Recognition of d- and l-Amino Acid Methyl Ester Hydrochlorides by New Chiral Bis-pyridino-18-crown-6 Substituted with Urea, and Diphenyl Groups

The article reports the synthesis and chiral recognition properties of a new chiral bis-pyridino-18-crown-6 (7), having urea, diphenyl, and allyloxy groups. The chiral bis-pyridino-18-crown-6 was prepared by a thirteen-steps procedure from the commercially available (S)-(+)-mandelic acid and chelidamic acid. The association constants (K _a) (1.33 × 10³–3.20 × 10³) for enantiomeric recognition of d- and l-amino acid methyl ester hydrochlorides using the chiral bis-pyridino-18-crown-6 have been examined by ¹H-NMR titration method in CDCl₃ at 25 °C. The chiral bis-pyridino-18-crown-6 showed higher association constants for the d-series amino acid methyl ester (d-AlaOMe, d-LeuOMe, d-MetOMe) hydrochlorides as compared to the corresponding l-series (l-AlaOMe, l-LeuOMe, l-MetOMe) hydrochlorides.     

l-DOPA production by immobilized tyrosinase

The production of l-DOPA using l-tyrosine as substrate, the enzyme tyrosinase (EC 1.14.18.1) as biocatalyst, and l-ascorbate as reducing agent for the o-quinones produced by the enzymatic oxidation of the substrates was studied. Tyrosinase immobilization was investigated on different supports and chemical agents: chitin flakes activated with hexamethylenediamine and glutaraldehyde as crosslinking agent, chitosan gel beads, chitosan gel beads in the presence of glutaraldehyde, chitosan gel beads in the presence of polyvinyl pyrrolidone, and chitosan flakes using glutaraldehyde as crosslinking agent. The last support was considered the best using as performance indexes the following set of immobilization parameters: efficiency (90.52%), yield (11.65%), retention (12.87%), and instability factor (0.00). The conditions of immobilization on chitosan flakes were optimized using a two-level full factorial experimental design. The independent variables were enzyme-support contact time (t), glutaraldehyde concentration (G), and the amount of enzyme units initially offered (U _C). The response variable was the total units of enzymatic activity shown by the immobilized enzyme (U _IMO). The optimal conditions were t=24 h, G=2% (v/v), and U _C=163.7 U. Under these conditions the total units of enzymatic activity shown by the immobilized enzyme (U _IMO) was 23.3 U and the rate of l-DOPA production rate was 53.97 mg/(L·h).     

<Superscript>99m</Superscript>Tc-labeling and molecular modeling of short dipeptide glycyl-<Emphasis Type="SmallCaps">l</Emphasis>-proline

Glycyl-l-proline (Gly-l-Pro) is the main degradation product of collagen and is a good diagnostic tool in various pathological conditions. The aim of this work was to prepare dipeptide Gly-l-Pro labeled with ^99mTc. Complex preparation was carried out under alkaline reaction conditions and its stability was assessed 10 and 120 min after preparation. The formation of two types of complex compounds was observed. High-performance liquid chromatography, paper electrophoresis, paper chromatography and thin layer chromatography were employed to monitor the formation of different complexes. Molecular modeling (semi-empirical method) was used to design their structure and composition. First complex cI with formula [TcO(Gly-l-Pro)]⁻¹ is unstable. After 120 min cI is completely transformed to complex cII with formula Tc(Gly-l-Pro)₃.     

Polystyrene‐Supported (Catecholato)oxorhenium Complexes: Catalysts for Alcohol Oxidation with DMSO and for Deoxygenation of Epoxides to Alkenes with Triphenylphosphine

Polymer‐supported catalysts offer practical advantages for organic synthesis, such as improved product isolation, ease of catalyst recycling, and compatibility with parallel solution‐phase techniques. We have developed the (carboxypolystyrene‐catecholato)rhenium catalyst 2 derived from tyramine (=4‐(2‐aminoethyl)phenol), which is effective for alcohol oxidation with dimethylsulfoxide (DMSO) and for epoxide deoxygenation with triphenylphosphine. The supported [Re(catecholato)]catalyst 2 is air‐ and moisture‐stable and can be recovered and used repeatedly without decreasing activity. The procedures work with non‐halogenated solvents (toluene). DMSO for Re‐catalyzed alcohol oxidation is inexpensive and safer for transport and storage than commonly used peroxide reagents. The oxidation procedure was best suited for aliphatic alcohols, and the mild conditions were compatible with unprotected functional groups, such as those of alkenes, phenols, nitro compounds, and ketones (see Tables 1 and 2). Selective oxidation of secondary alcohols in the presence of primary alcohols was possible, and with longer reaction time, primary alcohols were converted to aldehydes without overoxidation. Epoxides (oxirans) were catalytically deoxygenated to alkenes with this catalyst and Ph₃P (see Table 3). Alkyloxiranes were converted to the alkenes with retention of configuration, while partial isomerization was observed in the deoxygenation of cis‐stilbene oxide ( cis‐1,2‐diphenyloxirane). These studies indicate that supported [Re(catecholato)] complexes are effective catalysts for O‐atom‐transfer reactions, and are well suited for applications in organic synthesis.