Selective monoalkylation of p-tert-butylcalix-[4]-arene in a methyl carbonate ionic liquid.

Methyl carbonate ionic liquids are shown to readily mono-deprotonate p-tert-butylcalix-[4]-arenes initiating the formation of an organic mono-anionic p-tert-butylcalix-[4]-arate salt, methanol and carbon dioxide. These calix-[4]-arate salts have been successfully used in alkylation reactions with dialkyl sulfates and alkyl halides to form a mono-alkylated single product with high yield. This method avoids the common use of alkali metal bases such as caesium fluoride hence providing a safer and more selective synthetic route.

Spontaneous Substitutions at Phosphorus Trihalides in Imidazolium Halide Ionic Liquids: Grotthuss Diffusion of Anions?

PX compounds (X=Cl, Br, I) in imidazolium halide ionic liquids combine with the anion Z (Z=Cl, Br, I) of the solvent to form [PX Z] complex anions. These anions have a sawhorse shape in which the lone pair of the phosphorus atom fills the third equatorial position of the pseudotrigonal bipyramid. Theoretical results show that this association remains incomplete due to strong hydrogen bonding with the cations of the ionic liquid, which competes with the phosphorus trihalide for interaction with the Z anion.

Comparison of cartilage histopathology assessment systems on human knee joints at all stages of osteoarthritis development.

Objective: To compare the MANKIN and OARSI cartilage histopathology assessment systems using human articular cartilage from a large number of donors across the adult age spectrum representing all levels of cartilage degradation.

Design: Human knees (n=125 from 65 donors; age range 23-92) were obtained from tissue banks. All cartilage surfaces were macroscopically graded.

Effective lubrication of articular cartilage by an amphiphilic hyaluronic acid derivative.

Background: Intra-articular injection of hyaluronic acid based therapies is gaining popularity as a treatment option for non-operative management of patients with symptomatic osteoarthritis. Although there is an abundance of evidence for both biological and mechanical mechanisms of joint protection by hyaluronic acid, one clear intention of viscosupplementation is to reduce friction and wear by providing an extrinsic lubricant. We tested the in vitro friction response of a novel hyaluronic acid derivative that presents amphiphilic features to promote adhesion to the cartilage surface and thereby improve cartilage lubrication.