New methods and strategies for the stereocontrolled synthesis of polypropionate-derived natural products

Abstract

By using the stereoregulated aldol reactions of chiral enol borinates with aldehydes, the synthesis of elaborate segments of polypropionate-derived natural products can be readily achieved. Stereocontrol may originate from the chiral influence of the boron reagent, the starting ketone (dependent on substitution pattern and enol borinate geometry), and the aldehyde, or from some combination of these (multiple asymmetric induction). Subsequent elaboration of the p-hydroxy ketone adducts can then be performed with a high level of overall diastereoselectivity. Examples of these reactions are given in the context of the synthesis of various polypropionate-derived natural products, including antibiotics (oleandomycin, rifamycin S), antitumour agents (swinholide A), enzyme inhibitors (ebelactone A), and marine polypropionates (denticulatin A and B). © 1992 IUPAC