1‐exo‐Alkylidene‐2,3‐anhydrofuranoses: Valuable Synthons in the Preparation of Furanose‐Based Templates

Highly functionalized 1‐ exo ‐alkylidene‐2,3‐anhydro‐, and 1′‐halo‐1‐ exo ‐alkylidene‐2,3‐anhydrofuranoses can be prepared in four or five steps, respectively, from D ‐mannose. These compounds feature a variety of functionalities, including a double bond, an oxirane, an allylic oxirane and (in the case of the 1′‐halo derivative) an alkenyl halide. The reactivity of each functionality in these derivatives has been explored, and the usefulness of these substrates has been demonstrated with the preparation of furanose‐based carbohydrate templates with up to four sites of molecular diversity.