A considerable body of evidence has been accumulated on the importance of glycoproteins and glycolipids in biological phenomenon. A family of carbohydrates that plays an important role in the functionality of oligosaccharide chains of glycoconjugates is the sialic acids. Studies have shown that a significant link exists between the over-expression of sialylated epitopes, such as sialyl Lewis antigens, sialyl-T and sialyl-Tn, sialyl α-(2→6)-lactosaminyl structures, and polysialic acid, and the metastatic potential of a number of cancer cell lines. Chemotherapeutic intervention in the biosynthesis of sialic acid, and in particular of sialoglycoconjugates, could result in significant changes in the membrane properties and interaction potential of cells, including tumour cells. A key enzyme in the sialoglycoconjugate biosynthetic pathway is CMP-N-acetylneuraminate synthetase (CMAS), which is responsible for the essential activation of sialic acid (in humans, N-acetylneuraminic acid, Neu5Ac) to the nucleotide sugar form CMP-Neu5Ac. Research into CMAS could explore possible strategies to inhibit this enzyme, or to exploit its substrate specificity to create novel glycans for biotechnology. The research described in this PhD thesis is focused on the design, synthesis, and eventual biological and structural evaluation, of functionalized Neu5Ac derivatives and CMP-Neu5Ac mimetics as inhibitors of human and pathogenic bacterial [Neisseria meningitidis, serogroup B (NmB)] CMAS.