Palladium-Catalyzed Asymmetric Benzylation of Azlactones
作者:Barry M. Trost、Lara C. Czabaniuk
DOI:10.1002/chem.201302390
日期:2013.11.4
Asymmetric benzylation of prochiral azlactone nucleophiles enables the catalytic introduction of a benzyl group towards the synthesis of α,α‐disubstituted amino acids. Herein, we report an enantioselective palladium‐catalyzed process using chiral bis(diphenylphosphinobenzoyl)diamine (dppba) ligands. Naphthalene‐ and heterocycle‐based methyl carbonates react with a number of azlactones derived from
structures are described (Figs. 1–4), showing β-turn type-I geometries for dipeptides 4a, 5b, and 4c and an extended conformation for peptide 5c (Table 3). The conversion of the free amino acids 1a–c into suitably protected building blocks 11a–d and 15d,e for peptidesynthesis is discussed (Schemes 3 and 4).