Pd-Oxazolone complexes conjugated to an engineered enzyme: improving fluorescence and catalytic properties

Different Pd-complexes containing orthometallated push-pull oxazolones were inserted by supramolecular Pd-amino acid coordination on two genetically engineered modified variants of the thermoalkalophilic Geobacillus thermocatenolatus lipase (GTL). Pd-lipase conjugation was performed on the solid phase in the previously immobilized form of GTL under mild conditions, and soluble conjugated Pd-GTL complexes were obtained by simply desorbing by washing with an acetonitrile aqueous solution. Three different Pd complexes were incorporated into two different genetically modified enzyme variants, one containing all the natural cysteine residues changed to serine residues, and another variant including an additional Cys mutation directly in the catalytic serine (Ser114Cys). The new Pd-enzyme conjugates were fluorescent even at ppm concentrations, while under the same conditions free Pd complexes did not show fluorescence at all. The Pd conjugation with the enzyme extremely increases the catalytic profile of the corresponding Pd complex from 200 to almost 1000-fold in the hydrogenation of arenes in aqueous media, achieving in the case of GTL conjugated with orthopalladated 4a an outstanding TOF value of 27 428 min^-1. Also the applicability of GTL-C114 conjugated with orthopalladated 4b in a site-selective C-H activation reaction under mild conditions has been demonstrated. Therefore, the Pd incorporation into the enzyme produces a highly stable conjugate, and improves remarkably the catalytic activity and selectivity, as well as the fluorescence intensity, of the Pd complexes.

Synthesis of 2-Substituted 4-Arylidene-5(4H)-oxazolones as Potential Cytotoxic Agents in the Presence of Lemon Juice as a Biocatalyst

BACKGROUND

The oxazolone class of compounds is known to exert a profound effect on malignant cell proliferation, tumor angiogenesis and /or on the established neoplastic vasculature. Additionally, these compounds are generally known to have a low tendency to interact with DNA which is not common with most of the conventional cytotoxic agents. Thus, this class of compounds is of particular interest for the discovery and development of patient-friendly anticancer agents.

OBJECTIVE

The initial objective of this study was to synthesize and evaluate 2-substituted 4-arylidene- 5(4H)-oxazolones for their potential anticancer properties.

METHODS

A simple, mild and non-hazardous synthetic methodology has been developed for the preparation of 2-substituted 4-arylidene-5(4H)-oxazolones. The methodology involved lemon juice mediated condensation of N-acyl glycine derivatives including hippuric acid with arylaldehydes in PEG-400 under ultrasound irradiation. All the synthesized compounds were screened via an MTT assay for their potential cytotoxic properties in vitro using the cancerous cell lines e.g. K562 (human chronic myeloid leukemia), Colo-205 (human colon carcinoma), and A549 (human lung carcinoma) and a non-cancerous HEK293 (human embryonic kidney) cell line.

RESULTS

Compounds 3a, 3c and 3i showed promising growth inhibition against A549 cell line but no significant effects on HEK293 cell line, indicating their selectivity towards cancer cells. Moreover, their IC50 values suggested that all these compounds were comparable to the reference drug doxorubicin indicating their potential against lung cancer.

CONCLUSION

The 4-arylidene-5(4H)-oxazolone framework presented here could be a new template for the design and discovery of potential anticancer agents especially for lung cancer.

An expedient synthesis of oxazolones using a cellulose supported ionic liquid phase catalyst

A novel cellulose supported ionic liquid phase catalyst has been synthesized and effectively employed as a heterogeneous catalyst in the synthesis of oxazolones.

[Et3NH][HSO4]-mediated functionalization of hippuric acid: an unprecedented approach to 4-arylidene-2-phenyl-5(4H)-oxazolones

Facile, sustainable and economical synthesis of Erlenmeyer azlactones.

The Zwitterionic Imidazolium Salt: First Used for Synthesis of 4-Arylidene-2-phenyl-5(4H)-oxazolones under Solvent-Free Conditions

The zwitterionic imidazolium salt was prepared and characterized by1H NMR. It was first used for synthesis of azlactones via Erlenmeyer synthesis from aromatic aldehydes and hippuric acid under solvent-free conditions. It was found that aldehyde substituents play an important role in these reactions. Better conversions and therefore higher isolated yields were observed when electron-withdrawing groups (EWG-) were present in the aromatic aldehyde. Opposite results were shown when electron-donating groups (EDG-) were present in the aromatic aldehyde. However, azlactones were obtained in moderate to high yields.

Ultrasound-promoted a green protocol for the synthesis of 2,4-diarylthiazoles under ambient temperature in [bmim]BF(4)

A mild, efficient, facile and eco-friendly procedure for the synthesis of 2,4-diarylthiazoles from arylthioamides and alpha-bromoacetophenones in 1-n-butyl-3-methylimidazolium tetrafluoroborate as a "green" media under ultrasound irradiation at room temperature is described. It is interesting to mention that only one product was obtained when two different alpha-bromoacetophenones were reacted with 1,3-phenyl dithioamide as the substrate. Work-up is very simple and there is no need to purify the product. A recycling study confirmed that the ionic liquid can be reused multiple times without a significant loss in its activity.

(E)-4-(2,5-Dimethoxy-benzyl-idene)-2-phenyl-1,3-oxazol-5(4H)-one

The central aza­lactone ring in the title compound, C₁₈H₁₅NO₄, is planar (r.m.s. deviation 0.05, 0.12 Å) in both independent mol­ecules comprising the asymmetric unit. The benzyl­idene substituent is coplanar with this ring [dihedral angle between the planes = 1.8 (1)° in the first mol­ecule and 2.8 (1)° in the second], as is the phenyl substitutent [dihedral angle between rings = 4.6 (1) and 9.7 (1)°, respectively].