Stereocontrolled synthesis of spiroketals via Ti(Oi-Pr)4-mediated kinetic spirocyclization of glycal epoxides with retention of configuration.

A Ti(Oi-Pr)4-mediated kinetic spiroketalization reaction has been developed for the stereocontrolled target- and diversity-oriented synthesis of spiroketals. In contrast to most existing methods for spiroketal synthesis, this reaction does not rely upon thermodynamic control over the stereochemical configuration at the anomeric carbon. Stereochemically diverse glycals are first alkylated at the C1-position to introduce a hydroxyl-bearing side chain, then epoxidized stereoselectively.

Stereocontrolled synthesis of spiroketals via a remarkable methanol-induced kinetic spirocyclization reaction.

A methanol-induced kinetic spiroketalization reaction has been developed for the stereocontrolled target- and diversity-oriented synthesis of spiroketals. In contrast to existing methods for spiroketal synthesis, this reaction does not depend on thermodynamic product stability or require axial attack of an oxygen nucleophile. Stereodiverse glycals are alkylated at the C1 position with side chains bearing protected hydroxyl groups.

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.