title: Efficient Synthesis of Ephedra Alkaloid Analogues Using an Enantiomerically Pure N-[(R)-(+)-alpha-Methylbenzyl]aziridine-2-carboxaldehyde.
abstract: Efficient preparation of enantiomerically pure (2S)-aziridine-2-carboxaldehyde 9 and its 2(R) isomer and highly diastereoselective addition of organolithium reagents to the aldehyde 9 are described. The diastereoselectivity in additions of the lithium reagents seems to come from "chelation-controlled" carbon-carbon bond formation and is influenced by the source of the organometallic compound, solvent, and the presence of a Li salt. The C(3)-N bond of the aziridine ring of the addition products was regioselectively reduced by catalytic hydrogenation in the presence of Pearlman's catalyst to provide enantiomerically pure 1,2-amino alcohols. The absolute stereochemistries of the amino alcohol 13a were assigned as (1S,2S) when the C-1 substituent was phenyl by comparison with those of commercially available norpseudoephedrine.
authors.affiliation: Department of Chemistry, Sogang University, Seoul 121-742, Korea.
authors.forename: Gwon-Il
authors.initials: GI
authors.lastname: Hwang
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Chung
authors.forename: Won Koo
authors.initials: WK
authors.lastname: Lee