The key technology of SiaChem permits chemoenzymatic synthesis of (1) various natural sialic acids, (2) polysialic acids, (3) sialylglycans, (4) sialylglycan amino acids and (5) their derivatives, (6) sialidase substrates and inhibitors, (7) sialyltransferase donors and inhibitors, and (8) polymers, proteins and probes with defined sialic acids for basic research and biomedical development and applications.