反应详情

Surprisingly we found that the crucial feature of all successful transformations to Pemetrexed Disodium Form IV is the presence of Pemetrexed Monosodium during the transformation. Routes starting from pure Pemetrexed Disodium Heptahydrate, Pemetrexed Disodium 2.5 hydrate or Pemetrexed Disodium Form A in the presence of seeding crystals of Pemetrexed Disodium Form IV were not successful and resulted in isolation of Pemetrexed Disodium Form A. The same transformations, if carried out in the presence of 0.15 eq of Pemetrexed Monosodium were successful and after addition of 0.15 eq NaOH allowed the isolation of pure Pemetrexed Disodium Form IV. The use of 0.15 eq HCl instead of 0.15 eq Pemetrexed Monosodium under the same conditions resulted in isolation of Pemetrexed Disodium Form A without any Pemetrexed Disodium Form IV. Transformations via isolated Pemetrexed Monosodium gave complete transformation to Pemetrexed Disodium Form IV if either 1.0 eq NaOH were added slowly (over a period of several hours) to Pemetrexed Monosodium or if initially only 0.85 eq of NaOH (based on Pemetrexed Monosodium) were added, followed by 0.15 eq once the transformation to Pemetrexed Disodium Form IV was complete. Very fast addition (<1 min) of 1.0 eq NaOH resulted in formation of Pemetrexed Disodium Form A containing traces of Pemetrexed Disodium Heptahydrate.