title: A synthetic approach to diverse 3-acyltetramic acids via O- to C-acyl rearrangement and application to the total synthesis of penicillenol series.
abstract: For the efficient approach to medicinally important α-branched 3-acyltetramic acids, the key reaction of O- to C- acyl rearrangement using α-amino-acid-derived 4-O-acyltetramic acids was extensively examined in the presence of various metal salts. Use of CaCl(2) or NaI dramatically changed the results in the reaction efficiency and rapidly brought about the desired α-branched 3-acyltetramic acids in markedly improved yields. We also discuss an epimerization at C5 stereocenter under the rearrangement conditions as well as the tolerance for structural variation at C3 and C5. In addition to the preceding success in the total synthesis of new cytotoxic tetramic acid, penicillenol A(1), this methodology could be also applied to the first total synthesis of penicillenol A(2).
authors.affiliation: Department of Materials Science, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sengoku
authors.forename: Yuta
authors.initials: Y
authors.lastname: Nagae
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Ujihara
authors.forename: Masaki
authors.initials: M
authors.lastname: Takahashi
authors.forename: Hidemi
authors.initials: H
authors.lastname: Yoda
mesh_terms: D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D011760:Pyrrolidinones / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D011760:Pyrrolidinones; C575093:penicillenol A1; C575092:penicillenol A2; C009435:tetramic acid