Adaptable Fast Relaxing Boronate-Based Hydrogels for Probing Cell-Matrix Interactions.

Hydrogels with tunable viscoelasticity hold promise as materials that can recapitulate many dynamic mechanical properties found in native tissues. Here, covalent adaptable boronate bonds are exploited to prepare hydrogels that exhibit fast relaxation, with relaxation time constants on the order of seconds or less, but are stable for long-term cell culture and are cytocompatible for 3D cell encapsulation. Using human mesenchymal stem cells (hMSC) as a model, the fast relaxation matrix mechanics are found to promote cell-matrix interactions, leading to spreading and an increase in nuclear volume, and induce yes-associated protein/PDZ binding domain nuclear localization at longer times. All of these effects are exclusively based on the hMSCs' ability to physically remodel their surrounding microenvironment. Given the increasingly recognized importance of viscoelasticity in controlling cell function and fate, it is expected that the synthetic strategies and material platform presented should provide a useful system to study mechanotransduction on and within viscoelastic environments and explore many questions related to matrix biology.

Cu(I)-catalyzed synthesis of dihydropyrimidin-4-ones toward the preparation of ß- and ß3-amino acid analogues.

A copper(I)-catalyzed synthesis of substituted dihydropyrimidin-4-ones from propargyl amides via the formation of ketenimine intermediate has been successfully developed; the synthesis afforded good isolated yields (80-95%). The mild reaction conditions at room temperature allow the reaction to proceed to completion in a few hours without altering the stereochemistry. Further, by involving a variety of reactive nucleophiles, the obtained substituted dihydropyrimidin-4-ones were elegantly transformed into the corresponding ß- and ß(3)-amino acid analogues.