ABSTRACT
Sia found in nature. Further structural diversity is generated primar-ily by a combination of the above-mentioned variations at C-5 with modifications of any of the hydroxyl groups located at C-4, C-7, C-8, and C-9. For further information on Sia structure and diversity we highly recommend (Schauer and Kamerling, 1997; Angata and Varki, 2002; Chen and Varki, 2009).Due to their unique physiochemical properties, diversity of structure and exposed position, Sia have been implicated in numerous essential biological processes, such as neural cell growth and embryogenesis, stem cell biology, immune system regulation, human evolution, cancer progression, and microbial pathogenesis (Lehmann et al., 2006; Lanctot et al., 2007; Varki and Varki, 2007; Tiralongo, 2009).
