Super Silyl Stereo-Directing Groups for Complete 1,5-Syn and -Anti Stereoselectivities in the Aldol Reactions of β-Siloxy Methyl Ketones with Aldehydes

摘要

Polyketides are an important class of natural products, and then1,3-polyol motif is commonly found in these biologically significantncompounds.1 Undoubtedly, the asymmetric aldol reaction providesna straightforward route for the stereoselective construction of thesenrequired polyol subunits. We recently introduced a cascade Mukaiyamanaldol reaction based on super silyl and super Brønstednacid chemistry that gave the required polyol-carbonyls stereoselectivelynin a single step (Scheme 1A,B).2,3 To upgrade the cascadenprocess for even broader utility, such as rapid construction ofnpolyketide frameworks, we here focused on 1,5-stereoselective aldolnreactions that use our cascade products directly; these reactionsnrepresent a series of two consecutive aldol reactions of a centralnketone with two polyol-aldehydes (Scheme 1C).4,5