The present investigation involves the coordinative chain transfer polymerization (CCTP) of biobased terpenes in order to obtain sustainable polymers from myrcene (My) and farnesene (Fa), using the ternary Ziegler–Natta catalyst system comprising [NdV3]/[Al(i-Bu)2H]/[Me2SiCl2] and Al(i-Bu)2H, which acts as cocatalyst and chain transfer agent (CTA). The polymers were produced with a yield above 85% according to the monomeric consumption at the end of the reaction, and the kinetic examination revealed that the catalyst system proceeded with a reversible chain transfer mechanism in the presence of 15–30 equiv. of CTA. The resulting polyterpenes showed narrow molecular weight distributions (Mw/Mn = 1.4–2.5) and a high percent of 1,4-cis microstructure in the presence of 1 equiv. of Me2SiCl2, having control of the molecular weight distribution in Ziegler–Natta catalytic systems that maintain a high generation of 1,4-cis microstructure.
Packaging materials play an essential role in the preservation and marketing of food and other products. To improve their conservation capacity, antimicrobial agents that inhibit bacterial growth are used. Biopolymers such as starch and chitosan are a sustainable alternative for the generation of films for packaging that can also serve as a support for preservatives and antimicrobial agents. These substances can replace packaging of synthetic origin and maintain good functional properties to ensure the quality of food products. Films based on a mixture of corn starch and chitosan were developed by the casting method and the effect of incorporating cellulose nanocrystals (CNC) at different concentrations (0 to 10% w/w) was studied. The effect of the incorporation of CNC on the rheological, mechanical, thermal and barrier properties, as well as the antimicrobial activity of nanocomposite films, was evaluated. A significant modification of the functional and antimicrobial properties of the starch–chitosan films was observed with an increase in the concentration of nanomaterials. The films with CNC in a range of 0.5 to 5% presented the best performance. In line with the physicochemical characteristics which are desired in antimicrobial materials, this study can serve as a guide for the development this type of packaging for food use.
The overuse of fossil-based resources to produce thermoplastic materials and rubbers is dramatically affecting the environment, reflected in its clearest way as global warming. As a way of reducing this, multiple efforts are being undertaken including the use of more sustainable alternatives, for instance, those of natural origin as the main feedstock alternative, therefore having a lower carbon footprint. Contributing to this goal, the synthesis of bio-based rubbers based on β-myrcene and trans-β-farnesene was addressed in this work. Polymyrcene (PM) and polyfarnesene (PF) were synthesized via coordination polymerization using a neodymium-based catalytic system, and their properties were compared to the conventional polybutadiene (PB) and polyisoprene (PI) also obtained via coordination polymerization. Moreover, different average molecular weights were also tested to elucidate the influence over the materials’ properties. The crosslinking of the rubbers was carried out via conventional and efficient vulcanization routes, comparing the final properties of the crosslinking network of bio-based PM and PF with the conventional fossil-based PB and PI. Though the mechanical properties of the crosslinked rubbers improved as a function of molecular weight, the chemical structure of PM and PF (with 2 and 3 unsaturated double bonds, respectively) produced a crosslinking network with lower mechanical properties than those obtained by PB and PI (with 1 unsaturated double bond). The current work contributes to the understanding of improvements (in terms of crosslinking parameters) that are required to produce competitive rubber with good sustainability/performance balance.
Ajudazol B is a polyketide secondary metabolite, isolated from the myxobacterium Chondromyces crocatus, that exhibits potent biological activity. Herein, we report a convergent total synthesis of 8‐epi‐(–)‐ajudazol B. The key step is a regio‐selective alkylation and oxidative rearrangement of a reactive isobenzofuran intermediate that generates the isochromanone core. This approach provides a fast and efficient method to synthesise analogues of ajudazol B from simple aldehydes, allowing assessment of structure‐activity relationships. The antifungal activity of 8‐epi‐(–)‐ajudazol B as well as that of related analogues has been assessed using Botrytis cinerea. The results indicate that the isochromanone unit is key for antifungal activity.
Thalidomide has been one of the most studied molecules as a result of its anti-angiogenic and anti-inflammatory properties, despite its restrictions in the pharmaceutical market in the early 1960s due to its teratogenic effects. 1 As a consequence, a special interest in cyclic imides has been raised because they have an extensive range of biological activities, such as the capacity to cross out biological membranes in vivo. These cyclic imides derived from the general structure -CO-N(R)-CO-have neutral and hydrophilic properties. Therefore, the synthesis of the N-substituted isoindoline-1,3-dione compounds is a target for different groups in the area of medicinal chemistry. 2 Isoindoline-1,3-dione derivatives, phthalimides, have proved to be a significant source of compounds with anticancer properties acting as tumour necrosis factor alpha (TNF-α) inhibitors, allowing the preparation of new promising libraries. 3,4 In this regard, recent studies have demonstrated that molecules containing two phthalimide units increased both their antiinflammatory and anti-TNF-α activities, where the use of different spacers (shape and length) between the phthalimide rings provided the modulation of these properties. 5,6
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