Regioselectively Functionalized Cellulose Derivatives: A Mini Review

Summary: The paper reviews recent developments in synthesis and characterization of regioselectively functionalized cellulose derivatives. It demonstrates the importance of protecting groups like triphenylmethyl- and thexyldimethylsilyl (TDMS) ethers in cellulose chemistry. The protected cellulose derivatives can be used for the preparation of 2,3-O-functionalized polymers. Moreover, the TDMS group opens up the synthesis of 3-O-ethers of cellulose that possess interesting properties in terms of structure in solution, water-solubility, and thermoreversible gelation.     

Benefits and Detriments of Gadolinium from Medical Advances to Health and Ecological Risks

Gadolinium (Gd)-containing chelates have been established as diagnostics tools. However, extensive use in magnetic resonance imaging has led to increased Gd levels in industrialized parts of the world, adding to natural occurrence and causing environmental and health concerns. A vast amount of data shows that metal may accumulate in the human body and its deposition has been detected in organs such as brain and liver. Moreover, the disease nephrogenic systemic fibrosis has been linked to increased Gd³⁺ levels. Investigation of Gd³⁺ effects at the cellular and molecular levels mostly revolves around calcium-dependent proteins, since Gd³⁺ competes with calcium due to their similar size; other reports focus on interaction of Gd³⁺ with nucleic acids and carbohydrates. However, little is known about Gd³⁺ effects on membranes; yet some results suggest that Gd³⁺ interacts strongly with biologically-relevant lipids (e.g., brain membrane constituents) and causes serious structural changes including enhanced membrane rigidity and propensity for lipid fusion and aggregation at much lower concentrations than other ions, both toxic and essential. This review surveys the impact of the anthropogenic use of Gd emphasizing health risks and discussing debilitating effects of Gd³⁺ on cell membrane organization that may lead to deleterious health consequences.     

Mechanical properties of bulk single crystalline nanoporous gold investigated by millimetre-scale tension and compression testing

In this work, the mechanical behaviour of millimetre-scale, bulk single crystalline, nanoporous gold at room temperature is reported for the first time. Tension and compression tests were performed with a custom-designed test system that accommodates small-scale samples. The absence of grain boundaries in the specimens allowed measurement of the inherent strength of millimetre-scale nanoporous gold in tension. The elastic modulus and strength values in tension and compression were found to be significantly lower than values measured with nanoindentation-based techniques and previously reported in the literature, but close to those reported for millimetre-scale polycrystalline samples tested using traditional compression techniques. Fracture toughness was found to be very low, in agreement with the macroscopic brittleness of nanoporous gold, but this is due to the localization of deformation to a narrow zone of ligaments, which individually exhibit significant plasticity and necking.     

Short and efficient route toward α-substituted N-arylazetidines from acetanilides via Mitsunobu reaction

N-Arylazetidines are efficiently obtained in a three-step procedure, providing a wide diversity of derivatives on multigram scale with overall yields of 21–55%. Cheap or easily available acetanilides are used in an adapted aldolization with aldehydes, furnishing β-hydroxyamides with an 81% average yield over 21 examples. Special Mitsunobu conditions have been developed to ensure the cyclization of these hydroxyamides, giving β-lactams with an 73% average yield over 16 examples. A reduction then provided the N-arylazetidines in high yields.