Chemical Waltz of Organic Molecules "On Water": Saline-Assisted Sustainable Regioselective Synthesis of Fluorogenic Heterobioconjugates via Click Reaction

Geranyl Functionalized Materials for Site-Specific Co-Immobilization of Proteins

Different materials containing carboxylic groups have been functionalized with geranyl-amine molecules by using an EDC/NHS strategy. Chemical modification of the support was confirmed by XRD, UV-spectrophotometer, and FT-IR. This geranyl-functionalized material was successfully applied for four different strategies of site-selective immobilization of proteins at room temperature and aqueous media. A reversible hydrophobic immobilization of proteins (lipases, phosphoglucosidases, or tyrosinase) was performed in neutral pH in yields from 40 to >99%. An increase of the activity in the case of lipases was observed from a range of 2 to 4 times with respect to the initial activity in solution. When chemically or genetically functionalized cysteine enzymes were used, the covalent immobilization, via a selective thiol-alkene reaction, was observed in the presence of geranyl support at pH 8 in lipases in the presence of detergent (to avoid the previous hydrophobic interactions). Covalent attachment was confirmed with no release of protein after immobilization by incubation with hydrophobic molecules. In the case of a selenium-containing enzyme produced by the selenomethionine pathway, the selective immobilization was successfully yielded at acidic pH (pH 5) (89%) much better than at pH 8. In addition, when an azido-enzyme was produced by the azide-homoalanine pathway, the selective immobilization was successful at pH 6 and in the presence of CuI for the click chemistry reaction.

Synthesis and Operating Optimization of the PEG Conjugate via CuAAC in scCO2

A new sustainable green protocol for obtaining polyethylene glycol (PEG) conjugates, with a prototype molecule, which in this work was coumarin, by means of click chemistry is presented. The organic solvents commonly used for this type of reaction were replaced by supercritical carbon dioxide (scCO₂). The synthesis and characterization of PEG-coumarin were successfully reported using FTIR, ¹H NMR, and MALDI TOF. Subsequently, a preliminary study was carried out using the response surface methodology to examine the variables that most affect the use of scCO₂ as a reaction medium. The main effects caused by these variables, individually and their binary interaction, have been estimated. The response surface methodology has been used in this work to screen variables using a factorial design 2³. The p-values of temperature and pressure were 0.006 and 0.0117, being therefore the most significant variables of the response surface methodology study. Subsequently, a more intensive study has been carried out on the variables that have shown the greatest significant effect on reaction performance where an 82.32% synthesis success was achieved, which broadens the scope of the use of scCO₂ as a reaction medium. The conjugated coumarin with mPEG-alkyne and coumarin were evaluated for their in vitro antioxidant activities by the DPPH radical scavenging assay and were found to exhibit substantial activities. The click product showed comparable or even better efficacy than the initial coumarin.

Robust synthesis of sugar-coumarin based fluorescent 1,4-disubstituted-1,2,3-triazoles using highly efficient recyclable citrate grafted β-cyclodextrin@magnetite nano phase transfer catalyst in aqueous media

Green synthesis of 1,4-disubstituted-1,2,3-triazoles via click reaction using nano magnetic Fe₃O₄ core decorated with cyclodextrin-citric acid (Fe₃O₄@CD-CIT) acting as a phase transfer nanoreactor with low copper loading under ultrasonication at 40 °C, in aqueous media is described. Anchoring the surface of magnetite with cyclodextrin (CD) prevents its agglomeration and at the same time, CD provides a hydrophobic niche for lipophilic reactants while its outer hydrophilic core makes the reaction feasible in water yielding almost quantitative yield of desired products. Magnetic separation using an external magnet, recyclability and reuse (7 times), without appreciably affecting the %yield of the products are its other attractive attributes. Gram scale synthesis was also achieved with 93% yield.