Preparations of Seleno Sugar Derivatives

Preparations of Seleno Sugar Derivatives 1. Early Work 

The pioneering work of Wrede and co-workers,7-13 performed between 1917 and 1925, was rediscovered almost 30 years later by Bonner and Robinson14 during a synthetic approach to several selenoglycosides they used benzeneselenol in a classic Koenigs-Knorr reaction with tetra-0-acetyl-a-D-glucopyranosyl bromide (1). 

Wagner and Nuhn19 also detailed treatment of the l-seleno-/3-o-glucoside1112 with thiophosgene, a reaction which yielded a thiocyanato derivative after reaction with various classes of amine. 

Treatment of potassium salts 19 and 20 with sodium borohydride, followed by deacetylation, produced the diselenides 23 and 24 which, on treatment with metallic potassium in methanol, underwent cleavage of the Se-Se bond with formation of potassium salts 25 and 26. Products 19 and 20 are excellent precursors in the synthesis of symmetrical and unsymmetrical sugar selenides 27-32, as reported by Wagner and Nuhn.25 

It is noteworthy that all of the methods for the synthesis of selenoglycosides mentioned lead preferentially to the formation of the 1,2-trans prod- 

---