Synthesis of Andrographolide Glucopyranoside and Selective Cleavage ofO-acetyl Groups in Sugar Moiety

Andrographolide glucopyranosides were synthesized from andrographolide and tetra-O-acetyl-β-D-gluco- pyranosyl bromide via a Koenigs-Knorr reaction and deacetylation with a moderate deacetylation reagent dibutyltin oxide in methanol for the first time. The structures of the andrographolide derivatives were confirmed by IR, NMR, and HRMS. Deprotection of the acetylated andrographolide glucopyranoside with dibutyltin oxide in methanol selectively removed all acetyl groups of the sugar moiety, whereas the acetyl group of the andrographolide part and the base- or acid-sensitive functional groups were retained.