Stereoselective protecting group free synthesis of d,l-gulose ethyl glycoside via multicomponent enyne cross metathesis—hetero Diels–Alder reaction

An efficient and stereoselective synthesis of d,l-gulose was described. The key step of the synthetic route is represented by a multicomponent enyne cross metathesis—hetero Diels–Alder reaction which allows the formation of the pyran ring from cheap and commercially available substrates in a single synthetic step. The synthesis of d,l-gulose was accomplished without the use of protecting groups making this approach highly desirable also in terms of atom economy.