A series of sugar derivatives (7-14) were synthesized from stachyose, a sugar compound of Stachys sieboldi Miq, and evaluated for antibacterial activity against Mycobacterium tuberculosis, Mycobacterium avium, and Staphylococcus aureus, and their structure-activity relationships were studied. The results showed that the compound OCT359 (allyl O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl)-(1-->6)-O-(2,3,4-tri-O-acetyl-alpha-D-galactopyranosyl)-(1-->6)-O-2,3,4-tri-O-acetyl-beta-D-glucopyranoside) (12) exhibited in vitro antibacterial activity. The allyl group at C-1 and the acetoxy groups of the manninotrioside were requisite for the antibacterial activity.