Protective group-free synthesis of 3,4-dihydroxytetrahydrofurans from carbohydrates: formal total synthesis of sphydrofuran

► Olefination of unprotected carbohydrates with semi-stabilized Wittig reagents. ► Acid-catalyzed intramolecular cyclization of olefinic polyols. ► Stereoselective formation of 3,4-dihydroxytetrahydrofurans. ► Total formal synthesis of sphydrofuran.