The first synthesis of alphitonin-4-O-β-D-glucopyranoside (1) was described. Since, the nitrile group, a strong hydrogen bond acceptor with a significant solvation shell, is considered to have capacity comparable to sugar for facilitating the cell membrane permeation of the molecules, several alphitonin-4-O-β-D-glucopyranoside and maesopsin-4-O-β-D-glucopyranoside analogues were prepared by replacing glucopyranose moieties with acetonitrile groups. Immunostimulating activity evaluation on lymphocyte proliferation indicated that the compound 7 with an acetonitrile group at OH-4 of alphitonin had a strong stimulation effect on lymphocyte proliferation. Interestingly, when tested against the normal cell NIH/3T3, 7 had no inhibition even at the concentration of 100 µg/mL.