Enantioselective total synthesis of semperoside a |
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Authors: | Piccinini Paolo Vidari Giovanni Zanoni Giuseppe |
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Institution: | Dipartimento di Chimica Organica, Università di Pavia, Italy. |
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Abstract: | A versatile and concise strategy has been developed (Scheme 1) for the enantioselective synthesis of semperoside A 1 which is endowed with an unusually glucosylated iridane structure. The crucial step was a Hg(II)-mediated electrophilic heteroatom cyclization of beta-glucoside 4 that readily led to the iridane skeleton while installing the C-2 and C-3 stereocenters with complete stereocontrol. This expeditious route is unprecedented among synthetic approaches to iridoid glycosides and smoothly overcomes the hemiacetals glucosidation issue. The present inaugural total synthesis of semperoside A was achieved in 10 steps and 17% overall yield from the enantiomerically pure lactone 8, thus proving the absolute stereochemistry of 1 unequivocally. |
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