Patent ID: 6420552
Filing Date: 2002-07-16
Classification: C07H

Abstract:
A method of preparing a 4-O-alkyl chromogenic ketoside of N-acetylneuraminic acid (Neu5Ac), said method comprising, in order, the following steps:(a) simultaneously alkylating Neu5Ac on its C1 carboxyl and anomeric C2 hydroxyl to provide an alkyl ester alkyl ketoside derivative of Neu5Ac having 4-, 7-, 8-, and 9-hydroxyl groups; (b) protecting the 8- and 9-hydroxyl groups of the alkyl ester alkyl ketoside derivative of Neu5Ac to form a protected alkyl ester alkyl ketoside derivative of Neu5Ac; (c) alkylating the 4-hydroxyl group of the protected alkyl ester alkyl ketoside derivative of Neu5Ac by contacting the derivative with a composition comprising an alkyl halide to form a 4-O-alkyl protected alkyl ester alkyl ketoside derivative of Neu5Ac; (d) selectively deprotecting the 8- and 9-hydroxyl groups and dealkylating the 2-hydroxyl group of the ketoside product obtained in step (c), and derivatizing the resulting 2-, 7-, 8-, and 9-hydroxyl groups; (e) activating the anomeric carbon of the product obtained in step (d) to form a 4-O-alkyl alkyl ester derivative of Neu5Ac, derivatized at the 7-, 8- and 9-hydroxyls, and activated at the anomeric carbon; (f) contacting the product obtained in step (e) with a suspension of a chromogenic moiety in a solvent to form a chromogenic ketoside of a 4-O-alkyl alkyl ester derivative of Neu5Ac, derivatized at the 7-, 8- and 9-hydroxyls; and (g) obtaining a 4-O-alkyl chromogenic ketoside of Neu5Ac from the derivatized chromogenic ketoside obtained in step (f) by cleavage of the derivatized 7-, 8-, and 9-hydroxyls to regenerate the 7-, 8-, and 9-hydroxyl groups.