Ring Expansion of Cyclic Boronates via Oxyboration of Arynes.

The oxyboration of arynes was achieved for the first time. A series of 2-aryl-1,3,2-dioxaborolane derivatives were reacted with aryne precursors in the presence of CsF to give the corresponding ring-expanded seven-membered borinic acid esters via selective boron-oxygen bond activation. Preliminary experimental mechanistic studies and density functional theory (DFT) calculations suggest that this unprecedented aryne oxyboration proceeds through the formation of boron ate complexes of arylboronates with CsF, followed by aryne insertion into the boron-oxygen bond.

Copper(I)-Catalyzed Regio- and Stereoselective Silaboration of Terminal Allenes.

Organic compounds bearing both silyl and boryl groups are important building blocks in organic synthesis because of the adequate reactivity of the silyl and boryl groups and high stereospecificity in their derivatization reactions. The difference in reactivity between the silyl and boryl groups enables stepwise derivatization of these groups to afford complex molecules. Here, we report the copper(I)-catalyzed silaboration of terminal allenes to produce multisubstituted allylic boronates embedded with an alkenyl silane structure. The reaction can proceed with a variety of allenes and silylboranes. Furthermore, the silyl and boryl groups were successfully converted into other functional groups, while retaining the stereochemistry of the alkene moiety.

Development of effective antimicrobial cocktails to prevent bacterial contamination of allograft tissues under low temperature conditions.

OBJECTIVES: Prevention of bacterial transmission in recipient patients via allograft decontamination with an antimicrobial cocktail consisting of cefmetazole (cefoxitin), vancomycin, lincomycin and polymyxin B is an important procedure commonly practised in tissue banks. However, some allografts are lost due to the failure of decontamination under low temperature conditions. Here, we aimed to develop new antimicrobial cocktails that exert a high bactericidal activity at 4°C. METHODS: Bacterial species used in this study were selected as major causative pathogens of allograft tissue contamination. The efficacy of the combination of 2 antimicrobial agents was determined by the checkerboard titration method. The bactericidal effects of the new antimicrobial cocktails were evaluated under the same conditions as those used for the storage and preservation of allograft tissues. RESULTS: Among the selected antimicrobial agents, daptomycin exhibited the highest bactericidal activity against methicillin-resistant Staphylococcus aureus under low temperature conditions. The combination of daptomycin + gentamicin and daptomycin + levofloxacin showed a synergistic or additive effect against various bacterial species. The antimicrobial cocktail containing 200 µg/ml of daptomycin, gentamicin and levofloxacin could eradicate ≤104 colony-forming units/ml of methicillin-resistant S. aureus and Enterococcus faecalis, which exhibit a low susceptibility to antimicrobial agents at 4°C for 24 h. CONCLUSIONS: We have developed a new formula for an antimicrobial cocktail to effectively and sufficiently prevent bacterial contamination of allograft tissues under low temperature conditions in vitro.