title: Mechanism for the direct synthesis of tryptophan from indole and serine: a useful NMR technique for the detection of a reactive intermediate in the reaction mixture.
abstract: The reaction mechanism for the biomimetic synthesis of tryptophan from indole and serine in the presence of Ac(2)O in AcOH was investigated. Although the time-course (1)H-NMR spectra of the reaction of 5-methoxyindole with N-acetylserine were measured in the presence of (CD(3)CO)(2)O in CD(3)CO(2)D, the reactive intermediate could not be detected. This reaction was conducted without 5-methoxyindole in order to elucidate the reactive intermediate, but the intermediate could not be isolated from the reaction mixture. Since the intermediate would be expected to have a very short life time, and therefore be very difficult to detect by conventional analytical methods, the structure of the intermediate was elucidated using a 2D-NMR technique, diffusion-ordered spectroscopy (DOSY). Two intermediates were detected and confirmed to be 2-methyl-4-methyleneoxazol-5(4H)-one and 2-methyl-4-hydroxymethyloxazol-5(4H)-one. The present results demonstrated that DOSY is a powerful tool for the detection of unstable intermediates.
authors.affiliation: Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan. yokoyama@phar.toho-u.ac.jp
authors.forename: Yuusaku
authors.initials: Y
authors.lastname: Yokoyama
authors.forename: Masamichi
authors.initials: M
authors.lastname: Nakakoshi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Okuno
authors.forename: Yohko
authors.initials: Y
authors.lastname: Sakamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sakurai
mesh_terms: D000089:Acetic Anhydrides / Q000737:chemistry; D007211:Indoles / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D012694:Serine / Q000737:chemistry*; D014364:Tryptophan / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000089:Acetic Anhydrides; D007211:Indoles; C031800:acetic anhydride; D012694:Serine; C030374:indole; D014364:Tryptophan