Total Synthesis of (8S) and (8R) Methyl 8-β-d-Glucopyranosyl-Helianthenate B and Their Application for Other Derivatives

The first total synthesis of (8R) and (8S) methyl β-d-glucopyranosyl helianthenate B was accomplished using the Cadiot-Chodkiewicz coupling reaction as a key step. Significant differences were observed in the resonances between the 1H-NMR and 13C-NMR spectra of the diastereomers. Based on these results, the absolute configurations of glucopyranosyloxymethine in methyl β-d-glucopyranosyl helianthenate A to E (1-5) were reconfirmed to be the (R) configuration.