Microwave- and Thermally Promoted Iminyl Radical Cyclizations: A Versatile Method for the Synthesis of Functionalized Pyrrolines.

A detailed study of iminyl radical cyclizations of O-aryloximes tethered to alkenes is reported. The reactions can be triggered by either microwave irradiation or conventional heating in an oil bath. A variety of radical traps can be employed, enabling C-C, C-N, C-O, C-S, or C-X bond formation and producing a diverse array of functionalized pyrrolines. Substrates containing an allylic sulfide furnish terminal alkenes by a tandem cyclization-thiyl radical ß-elimination pathway. Cyclizations of hydroxylated substrates exhibit moderate diastereoselectivity that in some cases can partially be attributed to intramolecular hydrogen bonding. Computational studies suggested a possible role for thermodynamics in controlling the stereochemistry of cyclizations. The reaction temperature can be lowered from 120 to 100 °C by employing O-(p-tert-butylphenyl)oximes instead of O-phenyloximes as substrates, and these second-generation iminyl radical precursors can be used in a one-pot oxime ether formation-cyclization that is promoted by conventional heating. The functionalized pyrrolines obtained from these reactions can be conveniently transformed in several different ways.

Evaluation of the effects of repeated disinfection on medical exam gloves: Part 2. Changes in mechanical properties.

Many healthcare professionals have been forced, under acute shortages, to extend medical exam gloves beyond their intended single use. Despite limited available literature, the CDC proposed a set of guidelines for repeated exam gloves use, indicating a maximum number of treatments for three widely available disinfectants. This study examines how these treatments affect the mechanical properties of latex and nitrile gloves. Furthermore, an acceptability threshold is proposed for changes in tensile property, specifically elastic modulus, as an indication of degradation. This proposed criterion was also applied to similar studies available in the literature to determine applicability and aid in recommendation development. Three different latex glove brands and three nitrile brands were exposed to repeated treatments of an alcohol-based hand rub, diluted bleach, or soap and water. Tensile tests of samples cut from untreated and treated gloves were performed to assess the change in elastic modulus induced by each treatment. The findings suggest that latex gloves performed well within the CDC recommended guidelines of six repeated treatments for an ethanol-based hand rub and 10 repeated treatments of either dilute bleach or soap and water. Nitrile exam gloves, on the other hand, showed significant changes in elastic modulus, with more inconclusive results among brands. This was especially true for treatment with dilute bleach and soap and water. Further research is needed to investigate the effects of disinfection products on the mechanical integrity of nitrile exam gloves. The results support the use of five repeated treatments of ethanol-based hand rub for nitrile exam gloves, a lower threshold than currently recommended by the CDC. This research also supports that the CDC recommendation of 10 repeated treatment with soap and water is appropriate for latex exam gloves, but not for nitrile exam gloves. Occupational safety and health professionals involved in the selection of disposable exam gloves for infection control should consider the compatibility of the glove polymer type with available disinfectants, especially if extended use with repeated disinfection becomes necessary.

Synthesis and Studies of Bulky Cycloalkyl α,ß-Dehydroamino Acids that Enhance Proteolytic Stability.

Three new bulky cycloalkyl α,ß-dehydroamino acids (ΔAAs) have been designed and synthesized. Each residue enhances the rigidity of model peptides and their stability to proteolysis, with larger ring sizes exhibiting greater effects. Peptides containing bulky cycloalkyl ΔAAs are inert to conjugate addition by a nucleophilic thiol. The results suggest that these residues will be effective tools for improving the proteolytic stability of bioactive peptides.