title: Enantioselective synthesis of paraconic acids.
abstract: The development of a new method for the enantioselective synthesis of disubstituted gamma-butyrolactones is reported. Based on this strategy, the total synthesis of three paraconic acids, that is (-)-roccellaric acid, (-)-nephrosteranic acid and (-)-protopraesorediosic acid, and the formal total synthesis of (-)-methylenolactocin and (-)-protolichesterinic acid is described, which are important because of their antibiotic and antitumor properties. Key steps of the synthesis are copper(I)-catalyzed asymmetric cyclopropanations of furans, highly diastereoselective Sakurai allylations, Lewis acid or Lewis base catalyzed retroaldol/lactonization cascades, and ruthenium(II)-catalyzed, intermolecular cross metathesis reactions.
authors.affiliation: Institut für Organische Chemie, Universität Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
authors.forename: Rakeshwar B
authors.initials: RB
authors.lastname: Chhor
authors.forename: Bernd
authors.initials: B
authors.lastname: Nosse
authors.forename: Sebastian
authors.initials: S
authors.lastname: Sörgel
authors.forename: Claudius
authors.initials: C
authors.lastname: Böhm
authors.forename: Michael
authors.initials: M
authors.lastname: Seitz
authors.forename: Oliver
authors.initials: O
authors.lastname: Reiser