erythro-3-alkyl-2-hydroxypropionate unit in (4) is predominantly obtained via the reaction of but-2-enylstannane (2a) with glyoxylateesters (3) while the threo-isomer (5) is preferentially produced via 9-but-2-enyl-9-borabicyclo[3.3.1] nonane (2b); the former reaction has been applied to the enantioselective synthesis of verrucarinolactone (6).
The reaction of crotyltrialkylstannanes (1) with aldehydes in the presence of BF3,OEt2, produces the corresponding erythro homoallyl alcohols (2) predominantly regardless of the geometry of the double bond. Further, the Lewis acid mediated reaction exhibits the enhanced Cram selectivity in comparison with other allylic organometallic reactions which proceed in the absence of Lewis acids. Use of AlCl3-i-PrOH
Asymmetric [2,3]-Wittig Rearrangement Involving a Chiral Ester Enolate Terminus. A Chiral Synthesis of<i>erythro</i>-α-Hydroxy-β-alkyl Carboxylic Acid Derivatives
作者:Osamu Takahashi、Koichi Mikami、Takeshi Nakai
DOI:10.1246/cl.1987.69
日期:1987.1.5
The title rearrangement of the (E-2-alkenyloxy)acetic esters derived from (−)-8-phenylmenthol has been shown to afford the corresponding 3-alkyl-2-hydroxy-4-pentenoic ester with an extremely high level of diastereoface selection (95–97% de) along with a high erythro selectivity (90–93%).