Epoxides of D-fructose and L-sorbose: A convenient class of click functionality for the synthesis of a rare family of amino- and thio-sugars

The strained epoxide ring of oxirane-derived furanoside and pyranoside of D-fructose are regioselectively opened by various primary and secondary amines as well as azide to yield C4-alkylamino-C4-deoxy and the corresponding azido derivatives. The epoxide ring of a furanoside derived from L-sorbose, a C-5 epimer of D-fructose also afforded C4-amino and C4-azido analogues. All three epoxides generated piperazine linked disaccharides. These epoxides are also easily opened by p-tolylthiol to access thiosugars. One such thiosugar was converted to vinylsulfone-modified fructofuranoside and subjected to nucleophillic addition. A suitably designed vinyl sulfone-modified fructofuranoside having a leaving group at C-6, act as an efficient substrate for MIRC (Michael Initiated Ring Closure) reactions to construct cyclopropane skeleton in D-fructose. The strategy is general in nature and provides an easy access to cyclopropanated sugar derivatives. Thus, the easily accessible spring loaded epoxides of D-fructose and L-sorbose have been used as pivotal starting point for the synthesis of hitherto unknown modified carbohydrates.