Comparison theorems in Lorentzian geometry and applications to spacelike hypersurfaces

In this paper we prove Hessian and Laplacian comparison theorems for the Lorentzian distance function in a spacetime with sectional (or Ricci) curvature bounded by a certain function by means of a comparison criterion for Riccati equations. Using these results, under suitable conditions, we are able to obtain some estimates on the higher order mean curvatures of spacelike hypersurfaces satisfying a Omori-Yau maximum principle for certain elliptic operators.     

Enriching the Arsenal of Pharmacological Tools against MICAL2

Molecule interacting with CasL 2 (MICAL2), a cytoskeleton dynamics regulator, are strongly expressed in several human cancer types, especially at the invasive front, in metastasizing cancer cells and in the neo-angiogenic vasculature. Although a plethora of data exist and stress a growing relevance of MICAL2 to human cancer, it is worth noting that only one small-molecule inhibitor, named CCG-1423 (1), is known to date. Herein, with the aim to develop novel MICAL2 inhibitors, starting from CCG-1423 (1), a small library of new compounds was synthetized and biologically evaluated on human dermal microvascular endothelial cells (HMEC-1) and on renal cell adenocarcinoma (786-O) cells. Among the novel compounds, 10 and 7 gave interesting results in terms of reduction in cell proliferation and/or motility, whereas no effects were observed in MICAL2-knocked down cells. Aside from the interesting biological activities, this work provides the first structure–activity relationships (SARs) of CCG-1423 (1), thus providing precious information for the discovery of new MICAL2 inhibitors.     

C−H Fluoromethoxylation of Arenes by Photoredox Catalysis

Redox-active N-(fluoromethoxy)benzotriazoles were made accessible from fluoroacetic acid and hydroxybenzotriazoles via electrodecarboxylative coupling. After alkylation, they become effective monofluoromethoxylation reagents, enabling the photocatalytic C−H functionalization of arenes. Thus, irradiation of 1-(OCH₂F)-3-Me-6-(CF₃)benzotriazolium triflate with blue LED light in the presence of [Ru(bpy)₃(PF₆)₂] promotes the synthesis of diversely functionalized aryl monofluoromethyl ethers. This method allows the late-stage functionalization of biologically relevant structures without relying on ecologically problematic halofluorocarbons.     

Organocatalyzed Phospha-Michael Addition: A Highly Efficient Synthesis of Customized Bis(acyl)phosphane Oxide Photoinitiators

Addition of the P−H bond in bis(mesitoyl)phosphine, HP(COMes)₂ (BAPH), to a wide variety of activated carbon–carbon double bonds as acceptors was investigated. While this phospha-Michael addition does not proceed in the absence of an additive or catalyst, excellent results were obtained with stoichiometric basic potassium or caesium salts. Simple amine bases can be employed in catalytic amounts, and tetramethylguanidine (TMG) in particular is an outstanding catalyst that allows the preparation of bis(acyl)phosphines, R−P(COMes)₂, under very mild conditions in excellent yields after only a short time. All phosphines RP(COMes)₂ can subsequently be oxidized to the corresponding bis(acyl)phosphane oxides, RPO(COMes)₂, a substance class belonging to the most potent photoinitiators for radical polymerizations known to date. Thus, a simple and highly atom economic method has been found that allows the preparation of a broad range of photoinitiators adapted to their specific field of application even on a large scale.     

Thick Coating and Functionalization of Organic Surfaces via ATRP in Water

Atom‐transfer radical polymerization has been used for polymerizing water‐soluble monomers from solid polymeric particles, intended as a model for any polymeric functional surface. Depending on the polarity of substrate and solvent, homogeneous initiation throughout the particles or pure surface initiation could be obtained. In the last case, polymer layers were obtained with thicknesses up to several tens of microns, still active for block copolymerization.