Determination of etoposide phosphate intermediates by gradient liquid chromatography using postcolumn derivatization with cuprammonium hydroxide

Allyl 4,6-O-ethylidene-beta-D-glucopyranoside is an intermediate used in the synthesis of etoposide phosphate, a water-soluble derivative of the antineoplastic drug etoposide. In this paper, a method for the determination of allyl 4,6-O-ethylidene-beta-D-glucopyranoside and related glucopyranosides is described. Samples are analyzed by gradient high-performance liquid chromatography using postcolumn derivatization with cuprammonium hydroxide. The method is used to monitor the ethylidenation reaction of allyl beta-D-glucopyranoside with acetal to form allyl 4,6-O-ethylidene-beta-D-glucopyranoside. Samples are chromatographed on an octadecyl-bonded phase column with aqueous acetonitrile. Triethylamine is added to the mobile phase to accelerate mutarotation and suppress anomeric separations. The column effluent is mixed via a postcolumn tee with cuprammonium hydroxide and monitored with ultraviolet detection at 310 nm.