[Cl:1]N1C(=O)CCC1=O.[S:9]1[C:13]([C:14]2[N:22]3[C:17]([CH2:18][CH2:19][CH2:20][CH2:21]3)=[C:16]([C:23]([NH2:25])=[O:24])[CH:15]=2)=[CH:12][N:11]=[CH:10]1>C(#N)C.C(OCC)C>[Cl:1][C:15]1[C:16]([C:23]([NH2:25])=[O:24])=[C:17]2[N:22]([C:14]=1[C:13]1[S:9][CH:10]=[N:11][CH:12]=1)[CH2:21][CH2:20][CH2:19][CH2:18]2N-Chlorosuccinimide is added in 0.05 g portions to a solution of 0.1 g of 3-(5-thiazolyl)-5,6,7,8-tetrahydroindolizine-1-carboxamide in 10 cm3 of acetonitrile at 65° C. After 2 hours a precipitate is seen to form. The mixture is allowed to cool to approximately 20° C., the solid is filtered off and washed with two times 0.5 cm3 of acetonitrile. The operation was repeated another two times on 0.1 g of 3-(4-thiazolyl)-5,6,7,8-tetrahydroindolizine-1-carboxamide. The solids obtained in the three tests were combined and chromatographed on a column of 1.8 cm diameter containing 40 g of silica (0.063-0.220). Elution is carried out with a 95/5 mixture of dichloromethane and methanol, 2-cm3 fractions being collected. The homogeneous fractions are combined and concentrated at reduced pressure (2.7 kPa) at a temperature close to 40° C., to give a white solid which is taken up in ethyl ether and then filtered off and dried in air. 0.12 g of 2-chloro-3-(5-thiazolyl)-5,6,7,8-tetrahydroindolizine-1-carboxamide are thus obtained in the form of a white solid which melts at 227° C.
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