Abstract
A new synthetic route to 1,2‐pyran‐annulated O‐glycosides (pyranopyrans) with β‐manno configuration is presented. Starting from a benzyl‐protected allyl β‐2‐uloside obtained by C2‐oxidation from the corresponding allyl glucoside, vinylation and ring‐closing metathesis provided a bicyclic alkene as a key substrate. Optimized reaction conditions involving the 2‐uloside were required to circumvent the formation of the unwanted 3,2‐enolone. Subsequent stereoselective alkene dihydroxylations were investigated and are presented. Diastereoselective catalytic osmoylation afforded the bicyclic β‐mannoside with syn‐diol configuration. In contrast, a sequence featuring a directed vanadium‐catalyzed alkene epoxidation and epoxide opening provided the corresponding 2,10‐dioxadecalin target compound with trans‐diol configuration. X‐ray crystallography was employed to study the molecular structure of the target compound with syn‐diol configuration. In addition, the molecular packing and hydrogen‐bonding interactions of the hydroxy‐rich molecule were examined.
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