L-Proline → (S)-6-chloro-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10H)-dione

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Reaction Steps

10 g (50.6 mmol) of 6-chloroisatoic acid anhydride are stirred at 110° C. for 2 hours with 5.82 g (50.6 mmol) of L-proline in 80 ml of dimethyl sulphoxide. The solution is evaporated and the residue is crystallised from ethyl acetate. There is obtained (S)-6-chloro-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10H)-dione of melting point 264°-266° C. (b) A solution of 4.0 g (16 mmol) of (S)-6-chloro-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10)-dione in 30 ml of dimethylformamide is treated under an argon atmosphere with 0.57 g (16 mmol) of sodium hydride (60 percent oil dispersion) and stirred at room temperature for 1 hour. 3.02 g (17.5 mmol) of diethylchlorophosphate are added dropwise to the thus-obtained suspension at -20° C. and the mixture is stirred at this temperature for 10 minutes.

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