title: Reverse turn induced pi-facial selectivity during polyaniline-supported cobalt(II) salen catalyzed aerobic epoxidation of N-cinnamoyl L-proline derived peptides.
abstract: A novel chemo- and diastereoselective aerobic epoxidation of the N-cinnamoyl peptides catalyzed by polyaniline-supported cobalt(II) salen (PASCOS) is described. The N-cinnamoyl proline derived peptides 1 show a high pi-facial selectivity during these epoxidations. The origin of this diastereoselectivity in 1 has been attributed to (i) the propensity of the N-cinnamoyl proline amide to exist predominantly as trans rotamer in CDCl3, DMSO-d6, and CH3CN medium and (ii) existence of these peptides as organized structures (gamma- and beta-turns) due to the presence of intramolecular hydrogen bonds. An extensive solution NMR and MD simulation study on 1d and 1f indicates that the origin of the high pi-facial selectivity is due to the well-defined gamma- and beta-turns which result in the hindrance of one face of the cinnamoyl double bond in the transition state of the epoxidation reaction.
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, India, and Indian Institute of Chemical Technology, Hyderabad 500 007, India.
authors.forename: Jyoti Prokosh
authors.initials: JP
authors.lastname: Nandy
authors.forename: E N
authors.initials: EN
authors.lastname: Prabhakaran
authors.forename: S Kiran
authors.initials: SK
authors.lastname: Kumar
authors.forename: A C
authors.initials: AC
authors.lastname: Kunwar
authors.forename: Javed
authors.initials: J
authors.lastname: Iqbal
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000814:Aniline Compounds / Q000737:chemistry; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D000814:Aniline Compounds; D010455:Peptides; C416807:polyaniline; D003035:Cobalt; D011392:Proline