A novel process for the synthesis of pemetrexed disodium salt

摘要

The present invention relates to a novel process for the preparation of pemetrexed diethyl ester 2
which comprises the step of purifying the mixture obtainable by reacting compounds 1 and 1a in the presence of a chemical agent capable of promoting the formation of a peptide bond in an aprotic organic solvent
characterized in that the mixture is subjected to the following steps:
a) washing with a basic aqueous solution;
b) concentration of the organic phase;
c) addition of a polar organic solvent and/or a mixture of polar organic solvents;
d) precipitation of the pemetrexed diethyl ester 2 . The present invention relates also to a process for the preparation of the disodium salt 5
comprising the above-mentioned process for the preparation of pemetrexed diethyl ester 2 .
A further subject of the present invention is the crystalline form of pemetrexed diethyl ester 2 .