Sulfanyl radical promoted C4′–C5′ bond scission of 5′-oxo-3′,4′-didehydro-2′,3′-dideoxynucleosides

Treatment of C5′-aldehydes 4a,b under mildly basic conditions leads to the formation of 3′,4′-didehydroaldehydes 1a,b and furfural 2. Sulfanyl radical addition to 1a,b eventually gives rise to the lactones 11a,b through C4′–C5′ bond scission of the 1,2-dioxetane intermediates 10a,b.