Enantioselective synthesis of erythro-4-deoxyglycals as scaffolds for target- and diversity-oriented synthesis: new insights into glycal reactivity.

An efficient, enantioselective synthesis of erythro-4-deoxyglycals has been developed using asymmetric aldehyde allylation and tungsten-catalyzed alkynol endo-cycloisomerization as the key steps. These versatile synthetic scaffolds have been elaborated to a variety of products using stereoselective transformations that are complementary to those available using the corresponding threo glycals. This work has provided valuable insights into the relationships between glycal structure and reactivity. In addition, a new diene-forming side reaction during tungsten-catalyzed alkynol cycloisomerization has been discovered.