PURPOSE: To obtain the subject compound which is a raw material for a sialic acid-containing saccharide chain compound useful for efficiently synthesizing a ganglioside by carrying out a new method for treating a nest of a swallow with hydrazine and then N-acetylating a free amine.

CONSTITUTION: A nest of a swallow is initially subjected to the reducing treatment with hydrazine (preferably anhydrous hydrazine) to provide a free amine, which is then N-acetylated according to a method for reacting the free amine with acetic anhydride in the presence of sodium hydrogencarbonate. The objective compound is then usually isolated from the resultant product by thin-layer chromatography or ion exchange chromatography, etc. Furthermore, the treatment with the hydrazine is preferably carried out by heating the nest and hydrazine in a sealed tube. The hydrazine can be used in an amount of, e.g. 3-10 pts.wt. based on 1 pt.wt. nest of the swallow.