Reverse turn induced pi-facial selectivity during polyaniline-supported cobalt(II) salen catalyzed aerobic epoxidation of N-cinnamoyl L-proline derived peptides.
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.
Nandy
Jyoti Prokosh
JP
Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, India, and Indian Institute of Chemical Technology, Hyderabad 500 007, India.
Prabhakaran
E N
EN
Kumar
S Kiran
SK
Kunwar
A C
AC
Iqbal
Javed
J
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
D000596:Amino Acids; D000814:Aniline Compounds; D010455:Peptides; C416807:polyaniline; D003035:Cobalt; D011392:Proline