title: Asymmetric intramolecular [2 + 2] photocycloadditions: alpha- and beta-hydroxy acids as chiral tether groups.
abstract: Chiral alpha- and beta-hydroxy acids such as (S)-lactic acid, (S)-phenyllactic acid, (S)-mandelic acid, or (3R)-3-hydroxybutyric acid have been used as tether groups for intramolecular and diastereoselective [2 + 2] photocycloaddition of 3-oxocyclohexene carboxylic acid derivatives. Total regiocontrol toward the straight adduct and high diastereoselectivities (up to 94%) were observed in the case of butenyl lactate 11. After separation of the two diastereoisomers, cleavage of the chiral tether under basic conditions afforded cyclobutane lactones in good yield and enantiomeric pure form. An X-ray structure has been recorded that confirmed the relative and absolute configuration of the three contiguous stereogenic centers assigned according to CD spectra.
authors.affiliation: Laboratoire des Réactions Sélectives et Applications (CNRS, UMR 6519), Université de Reims-Champagne-Ardenne, B.P. 1039, F-51687 Reims Cedex, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Faure
authors.forename: Sylvie
authors.initials: S
authors.lastname: Piva-Le-Blanc
authors.forename: Cyrille
authors.initials: C
authors.lastname: Bertrand
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Pete
authors.forename: René
authors.initials: R
authors.lastname: Faure
authors.forename: Olivier
authors.initials: O
authors.lastname: Piva