Hetero Diels–Alder reactions of acyl phosphonates: synthesis of glycosyl type phosphonates

We have prepared glycosyl type phosphonates via hetero Diels–Alder (HDA) reactions of acyl phosphonates with electron rich dienes. HDA reactions of acyl phosphonates with Danishefsky’s diene required thermal activation to yield the desired dihydropyranones in good yield (70–91%). The reactions with Brassard’s diene involved Lewis acid promotion to yield the corresponding lactones, though in moderate yield (33–69%).