Stereoselective Synthesis of α‐Linked 2‐Deoxy Glycosides Enabled by Visible‐Light‐Mediated Reductive Deiodination

Abstract

2-Deoxy sugars and their derivatives occur abundantly in many pharmaceutically important natural products. However, the construction of specific 2-deoxy-glycosidic bonds remains as a challenge. Herein, we report an efficient way to prepare 2-deoxy-α-glycosides by glycosylation of 2-iodo-glycosyl acetate and subsequent visible-light-mediated tin-free reductive deiodination. We have successfully applied the postglycosylational-deiodination strategy in the synthesis of more than 30 mono-, di-, tri-, tetra- and pentadeoxysaccharides with excellent stereoselectivity and efficiency. This method has also been applied to the synthesis of a 2-deoxy-tetrasaccharide containing four α-linkages.

A One-Pot Method for Removal of Thioacetyl Group via Desulfurization under Ultraviolet Light To Synthesize Deoxyglycosides

“…The synthesis of deoxy sugars, especially the synthesis of 2-deoxyglycosides and their derivatives, has drawn increasing attention from carbohydrate chemists because many bioactive natural products have deoxyglycosides as the main constituents of glycosidic chains that play significant roles in bioactivity. − Usually, these deoxy carbohydrate derivatives were synthesized through the reduction of glycals, glyco-epoxides, glycosides with halides, − and glycosides with a thiocarbonyl group − and thioacetate group. , Recently, we have developed a method to obtain the deoxyglycosides through desulfurization of glycoside thiols under ultraviolet light (Scheme a) in order to overcome the shortcomings of Raney nickel catalyzed reduction of a thioacetate group. , In this method, the acylated substrates have to be deprotected in the first step to form glycosyl thiols, which is then desulfurized in the second step to form unprotected deoxy glycosides. This method may be limited in many applications in which acylated deoxyglycoside derivatives are key intermediates (Scheme b). − ,, Therefore, we wondered if we could develop a method for removal of a thioacetyl group via desulfurization under UV light to obtain acylated deoxyglycoside derivatives.…”

Deoxy sugars. General methods for carbohydrate deoxygenation and glycosidation

“…With the same effect as fluorine (Scheme 33) the introduction of iodine at C-2 offers the possibility of eliminating it after glycosidation by different methods. 186…”

Recent advances in photoinduced glycosylation: oligosaccharides, glycoconjugates and their synthetic applications

“…As a result, the usage of direct glycosylation in the preparation of complex 2-deoxy glycosides or natural products are rarely reported in the literature. 75 Wang and coworkers 76 described an efficient way to prepare 2-deoxy-aglycosides by the glycosylation of 2-iodo-glycosyl acetate and subsequent visible-light mediated tin-free reductive deiodination (Scheme 10). 2-Deoxy sugars and their derivatives widely appear in many pharmaceutically important natural products.…”