Stereocyt, Bellon ,France ,1978
p-[N-bis(β-chloroethyl)amino] phenyl butyric acid was dissolved in a mixture of 150 ml dry benzene and 8.04 ml dry pyridine. The solution was cooled in an ice bath, and a solution of thionyl chloride in 30 ml dry benzene was slowly added with stirring under anhydrous conditions.
The reaction mixture was then kept at room temperature for 1 hour and thereafter poured into a mixture of 5.0 N HCl and crushed ice. The benzene solution was immediately washed with water, with cold 1.0 N NaHCO3 and finally with cold water. After drying over anhydrous sodium sulfate, the benzene was removed in vacuo. The residue is the p-[N-bis(βchloroethyl)amino]phenyl butyric anhydride which could be used without any further purification.
To a solution of 42.0 g of p-[N-bis(β-chloroethyl)amino]phenyl butyric anhydride in 500 ml dry pyridine was added 24.4 g of prednisolone. The reaction mixture was kept at room temperature for 24 hours under anhydrous condition. It was then poured into a mixture of concentrated HCl and crushed ice and extracted with ether-ethyl acetate (1:1).
The organic phase was washed several times with cold 1.0 N K2CO3 and finallywater. After drying over CaCl2 the solvent was removed in vacuo.
The residue is prednisolone 21-[4'-[p-bis(β-chloroethyl)amino]phenyl]butyrate which after crystallization from methanol/water had a melting point of 163°C to 164°C.
