Protecting‐Group‐Free Synthesis in Carbohydrate Chemistry

The Stereoselective Total Synthesis of the Elusive Cephalosporolide F

“…As we are committed to the idea of performing asymmetric synthesis from cheap and available starting materials such as monosaccharides, under a protecting-free-group approach, we planned the synthesis of the octono-1,4-lactone derivative 3 from d -glucose and Meldrum’s acid. Subsequently, the preparation of alkoxyl radical precursor 2 would be completed by functionalizing the 1,2-diol moiety of 3 (Scheme ), which would feature a Wittig olefination for the chain elongation ( 3 → 4 ), a stereoselective Corey–Bakshi–Shibata reduction of 4 , and a Mitsunobu reaction of 5 for the incorporation of the N -alkoxyphthalimide group.…”

“…Accordingly, based on the work of Chen, regarding the generation of alkoxyl radicals from N-alkoxyphthalimides under visible-light photoredox catalysis, 10 we took the decision to use this methodology to prove our hypothesis. Consequently, we prepared the N-alkoxyphthalimide 2 as the alkoxyl radical precursor of ceph F. As we are committed to the idea of performing asymmetric synthesis from cheap and available starting materials such as monosaccharides, under a protecting-free-group approach, 11 we planned the synthesis of the octono-1,4-lactone derivative 3 from D-glucose and Meldrum's acid. Subsequently, the preparation of alkoxyl radical precursor 2 would be completed by functionalizing the 1,2-diol moiety of 3 (Scheme 3), which would feature a Wittig olefination for the chain elongation (3 → 4), a stereoselective Corey−Bakshi−Shibata reduction of 4, and a Mitsunobu reaction of 5 for the incorporation of the Nalkoxyphthalimide group.…”