Synthesis of Deoxy Sugars from Aldonolactones

Catalytic hydrogenation of benzoylated 3-deoxy-2-enono-1,5-lactones is stereoselective and affords the 3-deoxyaldonolactone derivatives, useful intermediates for the synthesis of deoxy sugars. Thus, 2,4,6-tri-0-benzoyl-3- 

When the benzoylated lactone 172a was debenzoylated with sodium methoxide and the product boiled in 1,4-dioxane, the more-stable 1,4-lactone 175 was isolated upon rebenzoylation. Reduction of the lactone carbonyl group afforded (220) the crystalline furanose derivative (176) of ascarylose. A similar procedure, performed on the benzoylated 3-deoxy-D-arabino-hexono-1,5-lactone 170, gave (221) the 3-deoxy-D-oraWno-hexo-furanose derivative. 

Catalytic hydrogenation (194) of butenolide 147, obtained from D-galac-tono-, D-glucono-, or D-mannono-1,4-lactones, afforded stereoselectively the 2,6-di-0-benzoyl-3,5-dideoxy-D,L-t/ira hexo no-1,4-lactone 177. 

Trideoxy sugars have also been prepared from aldono- 1,4-lactones. Thus, 2-0-benzoyl-3,5,6-trideoxy-a-D,L-t/ira hexofuranose was obtained (202) from L-rhamnono- 1,4-lactone via the furanone 155. L-Rhamnono-1,5-lac- 

Hydrogenation of the lactonic disaccharide 168 in the presence of triethylamine and palladium afforded (194) the 3-deoxylactone derivative 181. 

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