Synthesis of γ-monofluorinated goniothalamin analogues via regio- and stereoselective ring-opening hydrofluorination of epoxide.

A stereoselective synthesis of the biologically interesting γ-monofluorinated goniothalamin analogue 2a was described. The features of the synthesis included regioselective reduction of the unprotected hydroxypropynyl moiety of compound 10 by Red-Al, asymmetric Sharpless epoxidation of allyl alcohol 11, and regio- and stereoselective ring-opening hydrofluorination of the hydroxypropynyl epoxide 14 with Et(3)N·3HF in high ee and dr. The chiral hydroxypropynyl fluorohydrin 15 was used as a valuable building block for preparation of a range of γ-monofluorinated α,β-unsaturated δ-lactones.