Cycloadditions as a Sweet Route to ‘Double C-Glycosylation’

Pharmaceuticals, such as the antibiotic erythromycin, and sodium-dependent glucose transporter (SGLT1 & SGTL2) inhibitors such as Bexagliflozin (diabetes) and Sotagliflozin (heart disease), are often sugar-decorated (glycosylated). Glycosylation is a key component of the binding motif in SGLT inhibitors and, in natural products, glycosylation often confers improved bioactivity and bioavailability. Whilst a single <i>C</i>-glycoside link between a sugar moiety and its aglycone core is a common feature in natural products isolated to date, only a small number, including the antibiotics granaticin and sarubicin, are covalently bonded twice to a single sugar moiety. The way in which this "double <i>C</i>-glycosylation" is naturally mediated is not yet known, yet has been speculated on. Here, we report the exploration and development of a potentially biomimetic procedure that utilises intermolecular cycloaddition chemistry to access new "double <i>C</i>-glycosylated" products and enables the creation of bridged polycyclic ethers from a common maltol-derived oxidopyrylium salt precursor.