title: Enol ester as an olefinic partner in enyne cyclization. A novel tandem cyclization to stereodefined bicyclo[3.3.0]octenes.
abstract: When (Z)-1-tridecen-6-ynyl propanoate was treated with a titanium(II) alkoxide reagent, Ti(O-i-Pr)4/2i-PrMgCl, a novel tandem cyclization took place to give (1RS,2RS,3SR)-3-ethyl-4-hexyl-4-bicyclo[3.3.0]octene-2,3-diol virtually as a single stereoisomer after aqueous workup. The generality of this cyclization was also shown. Similarly, (Z)-3-butyl-1-tridecen-6-ynyl propanoate afforded (1RS,2RS,3SR,8SR)-8-butyl-3-ethyl-4-hexyl-4-bicyclo[3.3.0]octene-2,3-diol with a diastereoselectivity of >95:5, demonstrating the simultaneous construction of a total of four consecutive stereogenic centers in the product and with virtually complete diastereoselectivity.
authors.affiliation: Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan. hurabe@bio.titech.ac.jp
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Urabe
authors.forename: Daisuke
authors.initials: D
authors.lastname: Suzuki
authors.forename: Misa
authors.initials: M
authors.lastname: Sasaki
authors.forename: Fumie
authors.initials: F
authors.lastname: Sato