Biobased Terpene Derivatives: Stiff and Biocompatible Compounds to Tune Biodegradability and Properties of Poly(butylene succinate)

Different copolymers incorporating terpene oxide units (e.g., limonene oxide) have been evaluated considering thermal properties, degradability, and biocompatibility. Thus, polycarbonates and polyesters derived from aromatic, monocyclic and bicyclic anhydrides have been considered. Furthermore, ring substitution with myrcene terpene has been evaluated. All polymers were amorphous when evaluated directly from synthesis. However, spherulites could be observed after the slow evaporation of diluted chloroform solutions of polylimonene carbonate, with all isopropene units possessing an R configuration. This feature was surprising considering the reported information that suggested only the racemic polymer was able to crystallize. All polymers were thermally stable and showed a dependence of the maximum degradation rate temperature (from 242 °C to 342 °C) with the type of terpene oxide. The graduation of glass transition temperatures (from 44 °C to 172 °C) was also observed, being higher than those corresponding to the unsubstituted polymers. The chain stiffness of the studied polymers hindered both hydrolytic and enzymatic degradation while a higher rate was detected when an oxidative medium was assayed (e.g., weight losses around 12% after 21 days of exposure). All samples were biocompatible according to the adhesion and proliferation tests performed with fibroblast cells. Hydrophobic and mechanically consistent films (i.e., contact angles between 90° and 110°) were obtained after the evaporation of chloroform from the solutions, having different ratios of the studied biobased polyterpenes and poly(butylene succinate) (PBS). The blend films were comparable in tensile modulus and tensile strength with the pure PBS (e.g., values of 330 MPa and 7 MPa were determined for samples incorporating 30 wt.% of poly(PA-LO), the copolyester derived from limonene oxide and phthalic anhydride. Blends were degradable, biocompatible and appropriate to produce oriented-pore and random-pore scaffolds via a thermally-induced phase separation (TIPS) method and using 1,4-dioxane as solvent. The best results were attained with the blend composed of 70 wt.% PBS and 30 wt.% poly(PA-LO). In summary, the studied biobased terpene derivatives showed promising properties to be used in a blended form for biomedical applications such as scaffolds for tissue engineering.

A Bio-Based Alginate Aerogel as an Ionic Liquid Support for the Efficient Synthesis of Cyclic Carbonates from CO2 and Epoxides

In this work, the ionic liquid [Aliquat][Cl] was supported into alginate and silica aerogel matrices and applied as a catalyst in the cycloaddition reaction between CO2 and a bio-based epoxide (limonene oxide). The efficiency of the alginate aerogel system is much higher than that of the silica one. The method of wet impregnation was used for the impregnation of the aerogel with [Aliquat][Cl] and a zinc complex. The procedure originated a well-defined thin solvent film on the surface of support materials. Final materials were characterised by Fourier Transform Infrared Spectroscopy, N2 Adsorption–Desorption Analysis, X-ray diffraction, atomic absorption and Field Emission Scanning Microscopy. Several catalytic tests were performed in a high-pressure apparatus at 353.2 K and 4 MPa of CO2.

Kinetic Separation of cis-and trans-Limonene Epoxide: Reaction of Diastereomeric Mixture of Limonene Oxides with Secondary Amine and Carbamate

A simple kinetic separation of (1:1) diastereomeric mixture of limonene oxides was used to purify cis-and trans-diastereomers of (R)-(+)-limonene oxide. The epoxide ring of trans-isomer was selectively opened by (R)-N-methyl-(α-methyl-benzyl)amine. This secondary nucleophilic amine left cis-limonene oxide largely unreacted and was obtained up to 90% yield. In a diverse way, (R)-N-(α-methylbenzyl) ethyl carbamate, selectively catalyze hydrolysis of cis-limonene oxide to 1,2-limonene diol leaving trans-limonene oxide largely unreacted. The unreacted trans-limonene oxide was recovered in up to 75% yield. HPLC and NMR analyses were used to demonstrate that the isolation of cis-and trans-diastereomers of (R)-(+)-limonene oxide has shown that > 98% were pure. As a result, depending on the realization of the secondary amine or carbamate in the presence of water, either cis-or trans-limonene oxide may be obtained in high diastereomeric purity.

Sustainable block copolymers of poly(limonene carbonate)

Ring-opening copolymerization of lactide/lactide derivatives and trans-limonene oxide is used for the synthesis of sustainable block copolymers. The method alters the properties of bio-based, non-food-based poly(limonene carbonate).

Synthesis of bio-based poly limonene oxide with green catalyst

In the present work, the polymerization of limonene oxide (LO) catalyzed by Maghnite H+ (Mag- H+) is investigated. Mag-H+ is Algerian montmorillonite sheet silicate clay exchanged with protons. The poly limonene oxide (PLO) is obtained by cationic ring opening polymerization in bulk and with solvent. The effect of the reaction time, the temperature and the amount of catalyst are studied and discussed in order to find the optimal reactions conditions. The polymerization in solution at 0 °C with 5% by weight of catalyst leads to the best yield 61.34% for a reaction time of 1h. The structure of the obtained products is characterized by XRD, 1H-NMR, 13C-RMN, ATR-FTIR, DSC and TGA.

Catalytic Asymmetric Synthesis of P-Stereogenic Phosphines: Beyond Precious Metals

Metal-catalyzed asymmetric synthesis of P-stereogenic phosphines is a potentially useful approach to a class of chiral ligands with valuable applications in asymmetric catalysis. We introduced this idea with chiral platinum and palladium catalysts, exploiting rapid pyramidal inversion in diastereomeric metal–phosphido complexes (ML*(PRR′)) to control phosphorus stereochemistry. This Account summarizes our attempts to develop related synthetic methods using earth-abundant metals, especially copper, in which weaker metal–ligand bonds and faster substitution processes were expected to result in more active catalysts. Indeed, precious metals were not required. Without any transition metals at all, we exploited related P-epimerization processes to prepare enantiomerically pure phosphiranes and secondary phosphine oxides (SPOs) from commercially available chiral epoxides.1 Introduction2 Copper-Catalyzed Phosphine Alkylation3 Copper-Catalyzed Tandem Phosphine Alkylation/Arylation4 Nickel-Catalyzed Phosphine Alkylation5 Proton-Mediated P-Epimerization in Synthesis of Chiral Phosphiranes6 Diastereoselective Synthesis of P-Stereogenic Secondary Phosphine Oxides (SPOs) from (+)-Limonene Oxide7 Conclusions

Incubation with a Complex Orange Essential Oil Leads to Evolved Mutants with Increased Resistance and Tolerance

Emergence of strains with increased resistance/tolerance to natural antimicrobials was evidenced after cyclic exposure to carvacrol, citral, and (+)-limonene oxide. However, no previous studies have reported the development of resistance and tolerance to complex essential oils (EOs). This study seeks to evaluate the occurrence of Staphylococcus aureus strains resistant and tolerant to a complex orange essential oil (OEO) after prolonged cyclic treatments at low concentrations. Phenotypic characterization of evolved strains revealed an increase of minimum inhibitory and bactericidal concentration for OEO, a better growth fitness in presence of OEO, and an enhanced survival to lethal treatments, compared to wild-type strain. However, no significant differences (p > 0.05) in cross-resistance to antibiotics were observed. Mutations in hepT and accA in evolved strains highlight the important role of oxidative stress in the cell response to OEO, as well as the relevance of the cell membrane in the cell response to these natural antimicrobials. This study demonstrates the emergence of S. aureus strains that are resistant and tolerant to EO (Citrus sinensis). This phenomenon should be taken into account to assure the efficacy of natural antimicrobials in the design of food preservation strategies, in cleaning and disinfection protocols, and in clinical applications against resistant bacteria.