endo-Glycals are versatile building blocks in the preparation of numerous biomolecules and substrates for a variety of chemical transformations. The chemistry with regard to exo-glycals is less addressed in the literature. We demonstrate here the stereoselective synthesis of (Z)-exo-glycals from sugar lactones, as well as their reactivity and various applications. The additions of exo-glycals have been established to prepare novel glycosides and glycoconjugate with excellent stereoselectivity. This method will be exhibited to have serveral useful applications. In particular, the substituent of exo-glycals has been found to tremendously enhance the reactivity due to the extra driving force of allylic rearrangement.?
