25387-67-1

7689-03-4

25387-67-1

1.045 g of (S)-4-ethyl-4-hydroxy-1H-pyrano[3',4':6,7]indolizino[1,2-b]quinoline-3,14(4H,12H)-dione (CPT lactone) was accurately weighed in a sterile round bottom flask (250 mL). Water equivalent to 20% of the final volume was added to give a final concentration of CPT of 25 mM.Subsequently, 3.34 g of 1N NaOH solution was added to the inhomogeneous mixture, ensuring that the molar ratio of CPT to NaOH was 1:1.05.The mixture was stirred vigorously at 50°C until complete dissolution, a process that took about 1 h, indicating that the CPT lactone had been quantitatively converted to its water-soluble carboxylate form. It was shown that raising the temperature to 90°C further accelerated this conversion process. Although stirring for 4-6 hours has no significant effect on the chemical stability of CPT, it is recommended that this stirring time be maintained to ensure a complete reaction. Upon completion of the reaction, the solution is cooled to room temperature and can be stored under light conditions at 4°C for at least 24 hours. (Long-term storage stability of CPT-Na stock solutions will be discussed subsequently.) The pH of the final solution should be maintained between 10 and 11.5.