C-4 benzofuranylation of pyrazolones by a metal-free catalyzed indirect heteroarylation strategy.

A metal-free catalyzed indirect heteroarylation of pyrazolones with 2-(3-hydroxy-3,3-diarylprop-1-yn-1-yl) phenols has been developed, and a series of novel 4-benzofuranyl substituted pyrazolone derivatives were obtained in moderate to excellent yields (up to 90%). The process has the salient features of metal-free catalysis, operational simplicity, good substrate compatibility and mild reaction conditions. In particular, the integration of the pyrazolone skeleton and benzofuran scaffold into a single molecule is expected to be of potential interest for medicinal research. In addition, the yield and efficiency are basically maintained in the gram-scale experiment, which makes the practical application of the process more prominent.

Palladium-Catalyzed Asymmetric Trifluoromethylated Allylic Alkylation of Pyrazolones Enabled by α-(Trifluoromethyl)alkenyl Acetates.

The first asymmetric trifluoromethylated allylic alkylation of pyrazolones using α-(trifluoromethyl)alkenyl acetates as a novel trifluoromethylated allylation reagent is described, affording various functionalized chiral pyrazolones containing a trifluoromethylated allyl substituent in high yields with excellent regio-/enantio-/diastereoselectivities. Mechanistically, the double-bond migration of α-(trifluoromethyl)alkenyl acetates in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene is initial and interesting step. More importantly, this study is of significance in providing a novel and widely applicable trifluoromethyl-containing allylation reagent.

Catalytic asymmetric construction of C-4 alkenyl substituted pyrazolone derivatives bearing multiple stereoelements.

An organocatalytic asymmetric process was reported for the sterically precise construction of C-4 alkenyl substituted pyrazolone derivatives bearing multiple stereoelements. A series of interesting products featuring the union of a centrally chiral pyrazolone moiety and an axially chiral styrene unit were obtained in high yield with excellent diastereoselectivity and enantioselectivity (up to 99% ee, >20 : 1 dr). The process has the characteristics of mild reaction conditions, simple operation and broad substrate scope. The result of gram-scale reaction indicates that the reaction has good practicability.

Acid-catalyzed allenylation of pyrazolones with propargyl alcohols.

A TsOH-catalyzed allenylation of pyrazolones with propargylic alcohols has been developed. The established reaction system is well tolerated by a wide scope of pyrazolones and propargylic alcohols. The process has the salient features of operational simplicity, facile scale-up and high yield. In particular, the integration of the pharmaceutical-related pyrazolone skeleton and the allenyl group into a single molecule not only enriches the structural diversity of the pyrazolone scaffold, but potentially also contributes to a broader spectrum of biological activity. Furthermore, it is easy to synthesize 3aa in gram-scale with the yield and efficiency basically maintained, making the practical application of this process more prominent.

Synthesis of Sialic Acids, Their Derivatives, and Analogs by Using a Whole-Cell Catalyst.

Sialic acids (Sias) are important constituents of cell surface glycans. Ready access to Sias in large quantities would facilitate the development of carbohydrate-based vaccines and small-molecule drugs. We now present a facile method for synthesizing various natural forms and non-natural derivatives or analogs of Sias by using a whole-cell catalyst, which is constructed by adding a plasmid containing necessary enzyme genes into a metabolically engineered strain of Escherichia coli. The flexible substrate tolerance of incorporated enzymes (N-acetylglucosamine 2-epimerase and N-acetylneuraminic acid aldolase) allows the cellular catalyst to convert a wide range of simple and inexpensive sugars into various Sia-related compounds through an easily scalable fermentation process. Further, syntheses using this whole-cell biotransformation in combination with three conventional enzymatic reactions provide a series of complex Sia-containing glycans (sialyloligosaccharides) and their derivatives bearing different substituents. The processes described herein should permit the large-scale and economical production of both Sias and sialyloligosaccharides, and may complement existing chemical and enzymatic strategies.

Tuning the Poisson's Ratio of Biomaterials for Investigating Cellular Response.

Cells sense and respond to mechanical forces, regardless of whether the source is from a normal tissue matrix, an adjacent cell or a synthetic substrate. In recent years, cell response to surface rigidity has been extensively studied by modulating the elastic modulus of poly(ethylene glycol) (PEG)-based hydrogels. In the context of biomaterials, Poisson's ratio, another fundamental material property parameter has not been explored, primarily because of challenges involved in tuning the Poisson's ratio in biological scaffolds. Two-photon polymerization is used to fabricate suspended web structures that exhibit positive and negative Poisson's ratio (NPR), based on analytical models. NPR webs demonstrate biaxial expansion/compression behavior, as one or multiple cells apply local forces and move the structures. Unusual cell division on NPR structures is also demonstrated. This methodology can be used to tune the Poisson's ratio of several photocurable biomaterials and could have potential implications in the field of mechanobiology.

Femtosecond laser-assisted optoporation for drug and gene delivery into single mammalian cells.

In this work, focused near-infrared (NIR) femtosecond laser pulses were used to transiently perforate the cellular membrane of targeted human embryonic kidney (HEK) cells and the uptake of extrinsic molecules into the targeted cells was observed. Various cellular responses to the laser treatments were closely analyzed to optimize several experimental parameters such as laser power, exposure time and location of laser irradiation using a membrane impermeable fluorescent dye. The optimized parameters were used to investigate the entry of a plasmid DNA encoding green fluorescent protein (GFP) into the target cells. Since laser beam with higher-than-threshold energy level will disintegrate cells, we used Matlab simulations to characterize the laser irradiance and free electron distribution caused by the femtosecond-optoporation process. The simulation results showed that the free electron distribution is much narrower than the laser irradiance, which implies that the transient perforation can even be smaller than the size of the laser focal volume. Femtosecond laser-assisted optoporation when combined with lab-on-a-chip devices can be useful in single cell-based high-throughput screening.

Solid freeform fabrication of designer scaffolds of hyaluronic acid for nerve tissue engineering.

The field of tissue engineering and regenerative medicine will tremendously benefit from the development of three dimensional scaffolds with defined micro- and macro-architecture that replicate the geometry and chemical composition of native tissues. The current report describes a freeform fabrication technique that permits the development of nerve regeneration scaffolds with precisely engineered architecture that mimics that of native nerve, using the native extracellular matrix component hyaluronic acid (HA). To demonstrate the flexibility of the fabrication system, scaffolds exhibiting different geometries with varying pore shapes, sizes and controlled degradability were fabricated in a layer-by-layer fashion. To promote cell adhesion, scaffolds were covalently functionalized with laminin. This approach offers tremendous spatio-temporal flexibility to create architecturally complex structures such as scaffolds with branched tubes to mimic branched nerves at a plexus. We further demonstrate the ability to create bidirectional gradients within the microfabricated nerve conduits. We believe that combining the biological properties of HA with precise three dimensional micro-architecture could offer a useful platform for the development of a wide range of bioartificial organs.