| Sialic acids are a series of 2-keto-3-deoxy-nanonic acid, which have more than 50 naturally occurring members, the most common of which is N-acetyl Neuraminic acid. In nature, sialic acid is found at the terminal position of glycoconjugate chains and is usually attached to another sialic acid or a galactose molecule as ? glycosidic linkages. Sialic acid has been connected to a variety of biological functions, notably in cell-cell communication, oncogenesis, and cell mobility. For this diversity in biological functions sialic acid makes a great therapeutic target, and therefore is important not only to understand mechanism of sialylations to discover new ways of controlling the stereoselectivity of sialylation reaction and improve yields. Previously we reported the use of 2-Thio sialyl donor derivatives with TBDMS group at C-4, which lead to great stereocontrol. Herein we describe the introduction of novel protecting groups at C-4 and their testing as sialyl donors. Our preliminary results show that monochloroacetyl group is activating and ? stereocontrolling. |
