title: Asymmetric synthesis of (S)-(-)-xylopinine. Use of the sulfinyl group as an ipso director in aromatic SE.
abstract: Optically pure (S)-(-)-xylopinine 2 was prepared in three steps in 52% overall yield. Thus, condensation of the carbanion derived from (S)-4 with the (S)-(E)-sulfinylimine 5 gave a 2:1 mixture of tetrahydroisoquinolines 6a and 6b, differing only in configuration at sulfur. N-Desulfinylation of this mixture gave the diastereomeric sulfoxides which, without separation, were converted into (S)-(-)-xylopinine (2) with loss of the sulfinyl moieties under Pictet-Spengler conditions. This unprecedented ipso electrophilic substitution of a sulfinyl group may have synthetic implications beyond that described in this work.
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Cd. Universitaria, Coyoacán 04510, México D. F.
authors.forename: Virginia M
authors.initials: VM
authors.lastname: Mastranzo
authors.forename: Francisco
authors.initials: F
authors.lastname: Yuste
authors.forename: Benjamín
authors.initials: B
authors.lastname: Ortiz
authors.forename: Rubén
authors.initials: R
authors.lastname: Sánchez-Obregón
authors.forename: Rubén A
authors.initials: RA
authors.lastname: Toscano
authors.forename: José L
authors.initials: JL
authors.lastname: García Ruano
mesh_terms: D001600:Berberine Alkaloids / Q000138:chemical synthesis*; D015394:Molecular Structure; D013237:Stereoisomerism; D013452:Sulfonium Compounds / Q000737:chemistry*
chemical_list: D001600:Berberine Alkaloids; D013452:Sulfonium Compounds; C453820:xylopinine