Highly Stereoselective Synthesis of Multisubstituted Olefins from Alkynyl Tetracoordinate Borons and Iodonium Ylides via a Cyclic Intermediate.

We developed an intriguing and practical strategy for highly stereoselective assembly of multisubstituted olefins from alkynyl tetracoordinate boron species via a cyclic intermediate with 1,2-phenyl migration. We also developed a general method for the construction of deuterated trisubstituted alkenes from a cheap deuteration source, D2O, and the corresponding deuterated trisubstituted alkenes were obtained with excellent deuteration rates. This transformation features a novel reaction mechanism, exclusive stereoselectivity, and deuterated trisubstituted alkenes with excellent deuteration ratios.

Ni-catalysed assembly of axially chiral alkenes from alkynyl tetracoordinate borons via 1,3-metallate shift.

Asymmetric synthesis based on a metallate shift of tetracoordinate borons is an intriguing and challenging topic. Despite the construction of central chirality from tetracoordinate boron species via a 1,2-metallate shift, catalytic asymmetric synthesis of axially chiral compounds from such boron 'ate' complexes is an ongoing challenge. Axially chiral alkenes have received great attention due to their unique characteristics and intriguing molecular scaffolds. Here we report an enantioselective nickel-catalysed strategy for the construction of axially chiral alkenes via a 1,3-metallate shift of alkynyl tetracoordinate boron species. The chemoselectivity, regioselectivity and atroposelectivity can be regulated and well-controlled from readily accessible starting materials with a cheap transition-metal catalyst. Downstream transformations indicate the powerful conversion ability of such compounds in this protocol, and late-stage elaborations of bioactive compounds can also be achieved. Mechanistic experiments reveal that regioselective syn-addition of an aryl-Ni complex with a carbon-carbon triple bond and subsequent 1,3-phenyl migration are the two key steps for the synthesis of axially chiral alkenes.

Mesenchymal stem cells paracrine proteins from three-dimensional dynamic culture system promoted wound healing in third-degree burn models.

Recovery of skin function remains a significant clinical challenge for deep burns owing to the severe scar formation and poor appendage regeneration, and stem cell therapy has shown great potential for injured tissue regeneration. Here, a cell-free therapy system for deep burn skin was explored using mesenchymal stem cell paracrine proteins (MSC-PP) and polyethylene glycol (PEG) temperature-sensitive hydrogels. A three-dimensional (3D) dynamic culture system for MSCs' large-scale expansion was established using a porous gelatin microcarrier crosslinked with hyaluronic acid (PGM-HA), and the purified MSC-PP from culture supernatant was characterized by mass spectrometric analysis. The results showed the 3D dynamic culture system regulated MSCs cell cycle, reduced apoptosis, and decreased lactic acid content, and the MSC-PP produced in 3D group can promote cell proliferation, migration, and adhesion. The MSC-PP + PEG system maintained stable release in 28 days of observation in vitro. The in vivo therapeutic efficacy was investigated in the rabbit's third-degree burn model, and saline, PEG, MSC-PP, and MSC-PP + PEG treatments groups were set. The in vivo results showed that the MSC-PP + PEG group significantly improved wound healing, inhibited scar formation, and facilitated skin appendage regeneration. In conclusion, the MSC-PP + PEG sustained-release system provides a potentially effective treatment for deep burn skin healing.

Synthesis of α-Haloboronates by the Halogenation of gem-Diborylalkanes via Tetracoordinate Boron Species.

α-Haloboronates have a wide range of applications in organic chemistry as synthetic synthons; however, traditional synthetic methods of α-haloboronates are harsh and complicated. Herein, we used nBuLi as the nucleophilic reagent to attack the boron atom in gem-diborylalkanes to form tetracoordinate boron species and successfully achieved α-chloroboronates and α-bromoboronates with readily accessible electrophilic halogen reagents (NCS and NBS). The reaction is transition-metal-free and features a broad substrate scope and diversified valuable products.

Reconstructing auto tissue engineering lamellar cornea with aspartic acid modified acellular porcine corneal stroma and preconditioned limbal stem cell for corneal regeneration.

Tissue engineering cornea has shown great clinical potential for cornea reconstruction, but efficient recovery of natural structure and physiological function remains great challenges. In this study, the acellular porcine corneal stroma (APCS) was prepared by a phospholipase A2 decellularization method and further crosslinked with aspartic acid (Asp). The modified APCS-Asp scaffold showed significant increase of hydration degree, ultrastructure regularity, corneal viscoelasticity and anti-degradation ability compared to APCS. Autologous rabbit limbal tissue was pre-treated by tumor necrosis factor-alpha (TNF-α) and collagenase IV, and the pretreated primary limbal stem cells (LSCs) were cultured with embryonic stem cells conditioned medium (ESCM), and LSCs showed 3D cell sphere structure and improved stem cell properties compared to the control group. The auto-tissue engineering lamellar cornea (ATELC) was quickly reconstructed by using peptide hydrogel with a dynamic culture system. With intact and functional epithelial cell layer, the reconstructed ATELC quickly recovered natural optical characteristics 1 week post transplantation in the rabbit lamellar keratoplasty model and satisfying neural regrowth as well as favorable stromal repopulation were observed in the transplanted eyes in the 6 months following up post-surgery. In summary, this study provides a comprehensive optimized reconstruction strategy for ATELC, which maybe similar medical application to natural cornea.