title: Enantioselective total synthesis of octalactin a using asymmetric aldol reactions and a rapid lactonization to form a medium-sized ring.
abstract: Octalactin A, an antitumor agent containing an eight-membered lactone moiety, has been stereoselectively prepared by means of enantioselective aldol reactions of selected silyl enolates with achiral aldehydes, promoted by a chiral Sn(II) complex. The medium-sized lactone part was effectively constructed by way of a new and rapid mixed-anhydride lactonization using 2-methyl-6-nitrobenzoic anhydride (MNBA) with a catalytic amount of 4-(dimethylamino)pyridine (DMAP) or 4-(dimethylamino)pyridine 1-oxide (DMAPO). The use of only 5 mol % of DMAP or 2 mol % of DMAPO rapidly promoted formation of the medium-sized ring of the octalactin, demonstrating the remarkable efficiency of the new lactonization protocol.
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan. shiina@ch.kagu.tus.ac.jp
authors.forename: Isamu
authors.initials: I
authors.lastname: Shiina
authors.forename: Minako
authors.initials: M
authors.lastname: Hashizume
authors.forename: Yu-suke
authors.initials: YS
authors.lastname: Yamai
authors.forename: Hiromi
authors.initials: H
authors.lastname: Oshiumi
authors.forename: Takahisa
authors.initials: T
authors.lastname: Shimazaki
authors.forename: Yu-ji
authors.initials: YJ
authors.lastname: Takasuna
authors.forename: Ryoutarou
authors.initials: R
authors.lastname: Ibuka
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry; D007783:Lactones / Q000138:chemical synthesis* / Q000737:chemistry; D008968:Molecular Conformation; D013237:Stereoisomerism
chemical_list: D000970:Antineoplastic Agents; D007783:Lactones; C509477:cephalosporolide D; C509476:octalactin A; C509475:octalactin B