title: Regioselective Baeyer-Villiger oxidation in 4-carbonyl-2-azetidinone series: a revisited route toward carbapenem precursor.
abstract: A novel synthesis of acetoxyazetidinone 2 is presented. The azetidinone ring of compounds 7 is formed by C-3/C-4 cyclization of (2R,3R)-epoxybutyramide precursors 6, N-protected with a benzhydryl group. N-Deprotection by photoactivated bromination and acidic treatment leads to compounds 10 with various CO-R substituents at C-4. Transformation of these substituents by Baeyer-Villiger oxidation gives the desired regioisomer 11 with the cyclopropyl side-group which is the only group (among R = H, Ph, t-Bu, i-Pr, c-Pr) able to satisfy both the steric requirements of the cyclization step and the electronic requirements of the oxidative rearrangement step.
authors.affiliation: Unité de Chimie organique et médicinale, Université catholique de Louvain, Bâtiment Lavoisier, Place Louis Pasteur 1, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Laurent
authors.forename: Marcel
authors.initials: M
authors.lastname: Cérésiat
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Marchand-Brynaert