title: Opening of tartrate acetals using dialkylboron bromide: evidence for stereoselectivity downstream from ring fission.
abstract: Johnson-type acetals derived from dimethyl tartrate give, after opening with Me(2)BBr and cuprate displacement, secondary alcohols with high diastereoselectivity (>30:1). The mechanism proposed for the induction of diastereoselectivity is downstream from the ring fission. It implies a direct participation of the Lewis acid as a source of nucleophile and the stereospecific transformation of the resulting bromo acetal through an invertive and temperature-dependent process. The acetals are prepared by reaction of the desired aldehyde with dimethyl tartrate. Removal of the auxiliary is accomplished through SmI(2) reduction or by an addition-elimination protocol using methoxide.
authors.affiliation: Boehringer Ingelheim (Canada) Ltd., Bio-Méga Research Division, 2100 rue Cunard, Laval Québec, Canada H7S 2G5.
authors.forename: Yvan
authors.initials: Y
authors.lastname: Guindon
authors.forename: William W
authors.initials: WW
authors.lastname: Ogilvie
authors.forename: Josée
authors.initials: J
authors.lastname: Bordeleau
authors.forename: Wei Li
authors.initials: WL
authors.lastname: Cui
authors.forename: Kathy
authors.initials: K
authors.lastname: Durkin
authors.forename: Vida
authors.initials: V
authors.lastname: Gorys
authors.forename: Hélène
authors.initials: H
authors.lastname: Juteau
authors.forename: René
authors.initials: R
authors.lastname: Lemieux
authors.forename: Dennis
authors.initials: D
authors.lastname: Liotta
authors.forename: Bruno
authors.initials: B
authors.lastname: Simoneau
authors.forename: Christiane
authors.initials: C
authors.lastname: Yoakim