An improved synthesis of 3,6-anhydro-d-glucal and a study of its unusual chemical reactivity

•We developed an improved synthesis of 3,6-anhydro-d-glucal.•3,6-Anhydro-d-glucal was fully characterized and its crystal structure was determined.•Glycal addition reactions were studied with the unusual anhydroglycal.•A dianhydride sugar is formed from the reaction of anhydroglycal with NIS and DIPG. 6-O-Tosyl-d-glucal 1 upon treatment with excess LiAlH4 unexpectedly gave 3,6-anhydro-d-glucal 2 as a major product in good yield. A crystal structure was obtained. Reaction of the anhydride 2 with N-iodosuccinimide (NIS) in excess methanol resulted in the formation of diastereomeric 2-deoxy-2-iodoglycosides. Addition of ceric (IV) ammonium nitrate and thiophenol to a solution of 2 in acetonitrile gave a mixture of 2-deoxy and 2,3-unsaturated thioglycosides. Reaction of 1,2:3,4-di-O-isopropylidine-α-d-galactopyranose with the anhydro sugar 2 in the presence of N-iodosuccinimide did not give the expected iodoglycoside mixture, but instead gave an unusual 1,4:3,6-dianhydride 7 as the major product.