Enantioselective transformation of propargyl esters to dihydrofurans
摘要:
Transformation of enantiomerically enriched propargyl esters 5 into dihydrofurans 6 with complete enantiospecificity is achieved by Ag(I)-catalyzed rearrangement and cyclization, and the sequence is successfully applied to the enantioselective synthesis of an antitumor protective and hypolipidemic antibiotic, (S)-(-)-ascofuranone.
Synthesis of Enantiomerically Enriched 2,5-Dihydrofuran Derivatives from Easily Available Enantiomerically Enriched 2-Butyne-1,4-diols by Stereospecific Transformation
The transformation of enantiomericallyenriched 1,1,4-trisubstituted 4-acyloxy-2-butyn-1-ols 3 into 2,2,5-trisubstituted 3-acyloxy-2,5-dihydrofurans 5 with complete stereospecificity was achieved by an Ag(I)-mediated rearrangement of the monoesters 3 to allenic intermediates 4, followed by Ag(I)-assisted cyclization. A stereochemical analysis revealed that the newly formed carbon–oxygen bond in 5 was