title: Synthesis of sialic acid derivatives based on chiral substrate-controlled stereoselective aldol reactions using pyruvic acid oxabicyclo[2.2.2]octyl orthoester.
abstract: The synthesis of sialic acids and their analogs was accomplished based on substrate-controlled asymmetric aldol reactions between sterically complicated aldehydes easily prepared from commercially available carbohydrates and a novel pyruvic acid oxabicyclo[2.2.2]octyl orthoester. Systematic aldol reaction studies using chiral aldehydes revealed that α,β,γ-benzyloxy-substituted aldehydes with an α,β-anti relative configuration preferentially provided the Felkin products with the 4,5-anti configuration with high diastereoselectivity. The relative β,γ-configuration in α,β,γ-benzyloxy-substituted aldehydes with an α,β-syn arrangement exerted a secondary effect on the diastereoselectivity of the stereogenic center formed in aldol reactions, and α,β-syn-β,γ-anti benzyloxyaldehyde exhibited superior diastereoselectivity to α,β-syn-β,γ-syn benzyloxyaldehyde to yield the Felkin products.
authors.affiliation: Department of Pharmaceutical Sciences, Kitasato University, Tokyo 1088641, Japan. makinok@pharm.kitasato-u.ac.jp.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Norimura
authors.affiliation: Department of Pharmaceutical Sciences, Kitasato University, Tokyo 1088641, Japan. makinok@pharm.kitasato-u.ac.jp.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yamamoto
authors.affiliation: Department of Pharmaceutical Sciences, Kitasato University, Tokyo 1088641, Japan. makinok@pharm.kitasato-u.ac.jp.
authors.forename: Kazuishi
authors.identifier: http://orcid.org/0000-0001-8518-6593
authors.initials: K
authors.lastname: Makino