NATURAL-PRODUCTS SYNTHESIS UTILIZING FURAN-DERIVATIVES AS SYNTHONS

Furans have been recognized as useful intermediates in organic synthesis. Among the synthetic utilities of furans, 1,4-dicarbonyl equivalence is one of the characteristic features. This article describes the methodology for the synthesis of natural products, such as physiologically active steroids and lactonic antibiotics, employing the 1,4-dicarbonyl equivalents derived from furan derivatives. The synthetic strategy is based on oxidative conversion of chiral furfuryl alcohols into the pyranones followed by their functionalization with appropriate nucleophiles and electrophiles to provide the modified pyrans possessing desired stereochemistries. These intermediates have been transformed into withanolide and brassinolide side chains, styryl lactones such as goniothalamin and goniodiol, malyngolide, and canadensolide. Chiral furfuryl alcohols have been prepared as follows. 1) Diastereoselective addition of 2-lithiofurans to chiral carbonyl compounds. 2) Kinetic resolution of secondary furfuryl alcohols using Sharpless reagent.