Methods for manufacturing neuraminic acid compounds and synthetic intermediates of neuraminic acid compounds, including a method for manufacturing a compound represented by wherein R2 represents a C1-C4 alkyl, R3 represents a C1-C6 alkyl, R4 and R5 represent a hydrogen atom, a C1-C6 alkyl or a phenyl, or R4 and R5 together form a tetramethylene, a pentamethylene or an oxo, and Ac represents an acetyl, comprising reacting a compound represented by wherein R2 represents a C1-C4 alkyl, R3 represents a C1-C6 alkyl, R4 and R5 represent a hydrogen atom, a C1-C6 alkyl or a phenyl, or R4 and R5 together form a tetramethylene, a pentamethylene or an oxo, with trimethylsilyl azide in the presence of a Lewis acid.