Scalable Photocatalytic Oxidation of Methionine under Continuous-Flow Conditions

Photocatalytic Modification of Amino Acids, Peptides, and Proteins

In the last decade, visible‐light photoredox catalysis has emerged as a powerful strategy to enable novel transformations in organic synthesis. Owing to mild reaction conditions (i.e., room temperature, use of visible light) and high functional‐group tolerance, photoredox catalysis could represent an ideal strategy for chemoselective biomolecule modification. Indeed, a recent trend in photoredox catalysis is its application to the development of novel methodologies for amino acid modification. Herein, an up‐to‐date overview of photocatalytic methodologies for the modification of single amino acids, peptides, and proteins is provided. The advantages offered by photoredox catalysis and its suitability in the development of novel biocompatible methodologies are described. In addition, a brief consideration of the current limitations of photocatalytic approaches, as well as future challenges to be addressed, are discussed.

One-Pot Synthesis of Diverse γ-Lactam Scaffolds Facilitated by a Nebulizer-Based Continuous Flow Photoreactor

The use of a modified prototype continuous flow reactor (CFR) as a pivotal part of a number of versatile singlet oxygen-mediated reaction sequences is presented herein. These sequences target rapid access to structural complexity and diversity. The prototype reactor achieves high conversions and productivities by attaining large specific surface areas for these biphasic reactions. In the reactor, the reaction solution is nebulized (using either oxygen or air) and the resulting aerosol is irradiated by an LED jacket that surrounds the Pyrex reaction chamber. The one pot procedures developed herein are, according to many different criteria, both highly efficient and green. The key common intermediates and the source of both the complexity and variety of the final products are N-acyl imminium ions (NAI; protonated N-acyl enamines). The initial substrates are simple and readily accessible furans and the diverse array of products is composed of different complex γ-lactams. Many of the products are of particular interest due to their close relationships to known biologically active molecules.

Online monitoring of a photocatalytic reaction by real-time high resolution FlowNMR spectroscopy

We demonstrate how FlowNMR spectroscopy can readily be applied to investigate photochemical reactions that require sustained input of light and air to yield mechanistic insight under realistic conditions. The Eosin Y mediated photo-oxidation of N-allylbenzylamine is shown to produce imines as primary reaction products from which undesired aldehydes form after longer reaction times. Facile variation of reaction conditions during the reaction in flow allows for probe experiments that give information about the mode of action of the photocatalyst.

Simple low cost porphyrinic photosensitizers for large scale chemoselective oxidation of sulfides to sulfoxides under green conditions: targeted protonation of porphyrins

Large scale chemoselective photooxidation of sulfides to sulfoxides in the presence of the diacids ofmeso-tetra(phenyl)porphyrin with different acids is reported.