The oxidation of partially protected 2-acetamido-2-deoxypyranoses with silver carbonate on celite

GH47 and Other Glycoside Hydrolases Catalyze Glycosidic Bond Cleavage with the Assistance of Substrate Super-Arming at the Transition State

“…32 In other families, only one of the crystal structures shows binding of the substrate in the super-armed conformation. For example, while most GH22 lysozymes bind their substrates in the more relaxed 4 C 1 conformation, one crystal structure of M. lusoria GH22 lysozyme reveals a tetrasaccharide-based unsaturated lactone-type inhibitor bound in a 5 E conformation with pseudoaxial bonds at C4 and C5 distinct from the free solution E 5 conformation 73 of such lactones, indicating super-arming of the natural substrate (Figure 7d). Likewise, one crystal structure of a GH48 glucosidase holds a cellobio-derived isofagomine in the inverted 1 C 4 chair with the side chain in the gt conformation (Figure 7e).…”

Electrophilic Azidation for Stereoselective Synthesis of 2-Azido-2-deoxyaldono-1,5-lactones

“…Both methods yield 2-azido-2-deoxysugars, which are not only the precursors for 2-amino-2-deoxysugars but are also useful glycosyl donors in oligosaccharide synthesis in which α-linked 2-amino-2-deoxysugars are required . The aldonolactones are in general synthesized by oxidation of the corresponding aldoses . However, oxidation of 2-azido-2-deoxyaldoses is often accompanied by partial epimerization of the azido group. 6c, Alternatively, 2-azido-2-deoxyaldono-1,5-lactones can be prepared by the nucleophilic azide ion displacement of 2- O -sulfonate lactones, which also suffer a similar epimerization .…”

“…The aldonolactones are in general synthesized by oxidation of the corresponding aldoses . However, oxidation of 2-azido-2-deoxyaldoses is often accompanied by partial epimerization of the azido group. 6c, Alternatively, 2-azido-2-deoxyaldono-1,5-lactones can be prepared by the nucleophilic azide ion displacement of 2- O -sulfonate lactones, which also suffer a similar epimerization . It is reported that oxidation of 2-azido-3,4,6-tri- O -benzyl-2-deoxy- d -mannopyranose (i.e., 8 in Scheme ) resulted in a complete epimerization to the gluco isomer 6c.…”

“…However, oxidation of 2-azido-2-deoxyaldoses is often accompanied by partial epimerization of the azido group. 6c, Alternatively, 2-azido-2-deoxyaldono-1,5-lactones can be prepared by the nucleophilic azide ion displacement of 2- O -sulfonate lactones, which also suffer a similar epimerization . It is reported that oxidation of 2-azido-3,4,6-tri- O -benzyl-2-deoxy- d -mannopyranose (i.e., 8 in Scheme ) resulted in a complete epimerization to the gluco isomer 6c. The axial azide group at C-2 tends to epimerize during oxidation. 6c,, No practical route to 2-azido-2-deoxy- d -mannono-1,5-lactone (e.g., 7 ) has yet been reported.…”

“…It is reported that oxidation of 2-azido-3,4,6-tri- O -benzyl-2-deoxy- d -mannopyranose (i.e., 8 in Scheme ) resulted in a complete epimerization to the gluco isomer 6c. The axial azide group at C-2 tends to epimerize during oxidation. 6c,, No practical route to 2-azido-2-deoxy- d -mannono-1,5-lactone (e.g., 7 ) has yet been reported.

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