New 1-acyl-sialosyl-glycerol derivatives (1a-dα, 1a-dβ, 2α, 2β, which mimic the structure of the capusular polysaccharide of group C meningococcal were synthesized by the use of a chiral glycerol derivative, and were found to have phospholipases A₂ and C inhibitory activities. Furthermore, syntheses of 2-palmitoyl-sialosyl-glycerol derivative (4α, 4β, 5α, 5β), galactosyl-glycerol derivative (6), and sialosyl-galactosyl-glycerol derivative (7) were carried out to examine the difference between these activities. Among these sialosyl derivatives, 3-palmitoyl-sialosyl-glycerol derivatives (1-3α, 1-3β) demonstrated the most potent inhibitory activities.