title: Nitroxyl peptides as catalysts of enantioselective oxidations.
abstract: The achiral, nitroxyl-containing alpha-amino acid TOAC (TOAC = 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid), in combination with the chiral alpha-amino acid C(alpha)-methyl valine [(alphaMe)Val], was used to prepare short peptides (from di- to hexa-) that induced the enantioselective oxidation of racemic 1-phenylethanol to acetophenone. The best catalyst was an N(alpha)-acylated dipeptide alkylamide with the -TOAC-(alphaMe)Val- sequence folded in a stable, intramolecularly hydrogen-bonded beta-turn conformation with large, lipophilic (hydrophobic) N- and C-terminal blocking groups. We rationalized our findings by proposing models for the diastereomeric intermediates between (R)-[and (S)]-1-phenylethanol and the catalyst Fmoc-TOAC-L-(alphaMe)Val-NHiPr, based on the X-ray diffraction structure of the latter.
authors.affiliation: Department of Organic Chemistry, University of Padova, CNR Centre CSB, Italy.
authors.forename: Fernando
authors.initials: F
authors.lastname: Formaggio
authors.forename: Marcella
authors.initials: M
authors.lastname: Bonchio
authors.forename: Marco
authors.initials: M
authors.lastname: Crisma
authors.forename: Cristina
authors.initials: C
authors.lastname: Peggion
authors.forename: Stefano
authors.initials: S
authors.lastname: Mezzato
authors.forename: Alessandra
authors.initials: A
authors.lastname: Polese
authors.forename: Alessandra
authors.initials: A
authors.lastname: Barazza
authors.forename: Sabrina
authors.initials: S
authors.lastname: Antonello
authors.forename: Flavio
authors.initials: F
authors.lastname: Maran
authors.forename: Quirinus B
authors.initials: QB
authors.lastname: Broxterman
authors.forename: Bernard
authors.initials: B
authors.lastname: Kaptein
authors.forename: Johan
authors.initials: J
authors.lastname: Kamphuis
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Vitale
authors.forename: Michele
authors.initials: M
authors.lastname: Saviano
authors.forename: Ettore
authors.initials: E
authors.lastname: Benedetti
authors.forename: Claudio
authors.initials: C
authors.lastname: Toniolo
mesh_terms: D000098:Acetophenones / Q000737:chemistry; D000598:Amino Acids, Cyclic / Q000737:chemistry; D000621:Aminoisobutyric Acids / Q000737:chemistry; D002384:Catalysis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003497:Cyclic N-Oxides / Q000138:chemical synthesis* / Q000737:chemistry; D003509:Cyclohexanecarboxylic Acids / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009589:Nitrogen Oxides / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction; D010626:Phenylethyl Alcohol / Q000737:chemistry; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D013113:Spin Labels; D013237:Stereoisomerism; D014633:Valine / Q000031:analogs & derivatives / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000098:Acetophenones; D000598:Amino Acids, Cyclic; D000621:Aminoisobutyric Acids; C448019:C(alpha)-methyl valine; D003497:Cyclic N-Oxides; D003509:Cyclohexanecarboxylic Acids; D009589:Nitrogen Oxides; D009842:Oligopeptides; D013113:Spin Labels; C014966:1-aminocyclohexanecarboxylic acid; C039900:nitroxyl; D014633:Valine; D010626:Phenylethyl Alcohol; C038699:acetophenone; C037109:2,2,6,6-tetramethylpiperidine-N-oxide-4-amino-4-carboxylic acid