Enantioselective Allylation of Indoles: A Surprising Diastereoselectivity.

Herein we show a novel approach toward the allylation of indoles. Thereby, we explore a class of bench-stable allylboronates and fine-tune their reactivity. The allylations of different substituted indoles proceed with negligible diastereo- and excellent enantioselectivities. This surprising selectivity (up to 99:1 er, up to ≈60:40 dr) is rationalized by DFT calculations.

Philicity of Acetonyl and Benzoyl Radicals: A Comparative Experimental and Computational Study.

In this work, the reactivities of acetonyl and benzoyl radicals in aromatic substitution and addition reactions have been compared in an experimental and computational study. The results show that acetonyl is more electrophilic than benzoyl, which is rather nucleophilic. A Hammett plot analysis of the addition reactions of the two radicals to substituted styrenes clearly support the nucleophilicity of benzoyl, but in the case of acetonyl, no satisfactory linear correlation with a single substituent-related parameter was found. Computational calculations helped to rationalize this effect, and a good linear correlation was found with a combination of polar parameters (σ+ ) and the radical stabilization energies of the formed intermediates. Based on the calculated philicity indices for benzoyl and acetonyl, a quantitative comparison of these two radicals with many other reported radicals is possible, which may help to predict the reactivities of other aromatic radical substitution reactions.

Electron Beam Immobilization of Novel Antimicrobial, Short Peptide Motifs Leads to Membrane Surfaces with Promising Antibacterial Properties.

In this study, the efficacy of electron beam irradiation versus chemical coupling for yielding polyethersulfone (PES) membranes with antibacterial properties was investigated. For the surface coating, a recently discovered lead compound, IL-KKA, comprising a short peptide sequence functionalized with imidazolium groups, was used. For better integration within the membrane, several novel variants of IL-KKA were generated. Membrane immobilization was achieved using different doses of electron beam irradiation and NHS/EDC chemical coupling. Physicochemical characterization of the coated membranes was performed by water contact angle measurements, X-ray photoelectron spectroscopy, and scanning electron microscopy. Our results show that electron beam irradiation is as effective and gentle as chemical coupling using the NHS/EDC method. Moreover, it was demonstrated that the obtained membranes exhibit promising antibacterial activity against B. subtilis. In summary, the technique presented herein might be promising as a template for developing future anti-biofilm devices.

Highly Enantioselective Allylation of Ketones: An Efficient Approach to All Stereoisomers of Tertiary Homoallylic Alcohols.

An optimized protecting group for allylboronates allowed the use of ketones in order to synthesize all isomers of quaternary homoallylic alcohols with high enantioselectivities. All symmetric isomers of the allylboronate were prepared in high yields and diastereoselectivities using Sn 2' reactions. The improved reactivity of the novel protecting group was verified by following the reaction kinetics with 1 H NMR spectroscopy. Mechanistic studies using DFT calculations were conducted to investigate the new findings. Thus, the stereochemical outcome and enhanced reactivity can be rationalized.