A drug conjugate intermediate and its preparation method

Abstract

This invention discloses a drug conjugate intermediate and its preparation method. Specifically, this invention provides a method for preparing a compound of formula (II) or a salt thereof, comprising the following steps: Step 1, in a solvent and in the presence of a deprotecting agent, performing a deprotecting reaction as shown below to obtain a compound of formula (III) or a salt thereof; Step 2, in a solvent and in the presence of a condensing agent, performing an GP3 protecting reaction as shown below to obtain a compound of formula (II) or a salt thereof. The preparation method of this invention is low in cost, high in yield, and simpler to operate, making it suitable for large-scale production.