Structural establishment of polygalatenosides A and B by total synthesis

The first total synthesis of polygalatenosides A (1) and B (2), originally isolated from the traditional Chinese medicine and reported as antidepressant agents, is described here. Glycosylation between thiogalactosyl donors 6 and 7 and 1-deoxyglucosyl acceptor 5 yielded the corresponding key intermediates 10 and 16, respectively, with an α(1→2)-glycosidic linkage in moderate yields. In addition, d-configuration of the galactoside residue in 1 and 2 was confirmed in our studies.