One‐Pot Conversion of Amino Acids into 2,5‐Disubstituted Oxazoles: No Metals Needed

Abstract

2,5-Disubstituted oxazoles with a variety of alkyl and aryl groups are efficiently formed from N-acylamino acids, by a one-pot radical decarboxylation-oxidation-enolization and iodine-promoted cyclization process. Remarkably, the reaction takes place under mild conditions, and no metal catalysis is needed. The process can be useful for the direct modification of small peptides.

Protein‐Rich Biomass Waste as a Resource for Future Biorefineries: State of the Art, Challenges, and Opportunities

“…This approach provides opportunities for the development of pharmaceuticals, agrochemicals and other fine chemicals. Scheme shows several examples of synthetic routes towards amino acid‐derived pyridines (routes A–C), thiazoles (route D), oxazoles (routes E and F), quinazolines (route G), quinazolin‐4(3 H )‐ones (route H), quinolines (route I), and imidazo[1,5‐ a ]‐N‐heterocycles (routes J and K) …”

Site-selective modification of peptide backbones

“…A method for the formation of oxazole rings that does not involve serine or hydroxylated unit, and that can be applied to any residue in a terminal C-position, is shown in Scheme 30 (conversions 111→115 and 116→117). 101 Thus, decarboxylation of substrate 111 on treatment with a (diacyliodo)benzene and iodine generated an iminium ion 112 which isomerized to an enamide. The latter underwent an intramolecular halocyclization involving an adjacent amide carbonyl group (113114).…”

Recent Progress in Iodine‐Catalysed C−O/C−N Bond Formation of 1,3‐Oxazoles: A Comprehensive Review

“…Boto and co‐workers [72] reported a novel one‐pot metal‐free synthesis of 2,5‐disubstituted oxazoles 110 by iodine‐mediated radical de‐carboxylation oxidative cyclization of alkyl or aryl N‐acylated amino acid 109 (Scheme 41). The reaction feasibility was accessed by using iodine, additive and N‐benzoyl phenylalanine as the substrate under heating/visible light radiation to construct 2,5‐diphenyl oxazoles.…”