Expeditious synthesis of new 3,4,6-trihydroxythiepanes from D-(-)-quinic acid

We report herein that the new seven-membered-ring thiosugars (thiepanes) have been synthesized from D-(-)-quinic acid. The key feature of the synthesis involves the thiocyclization of protected hexane-1,2,3,5,6-pentanol derivatives. The subsequent step of acidic removal of protecting groups is critical in the reaction conditions to obtain the required 3,4,6-trihydroxythiepanes. During the course of studies, the unexpected trihydroxythiopyrans are formed because of the ring contractions of their corresponding trihydroxythiepanes under various conditions.