NC1C=CC(C(N[C@@H](CCSC)C(OC)=O)=O)=C(CC2C=CC=CC=2)C=1.[OH2:27].[OH2:28].[Cr](O[Cr]([O-])(=O)=O)([O-])(=O)=O.[Na+].[Na+].[Br:40][C:41]1[CH:46]=[C:45]([N+:47]([O-:49])=[O:48])[CH:44]=[CH:43][C:42]=1[CH3:50].S(=O)(=O)(O)O>C(O)(=O)C>[Br:40][C:41]1[CH:46]=[C:45]([N+:47]([O-:49])=[O:48])[CH:44]=[CH:43][C:42]=1[C:50]([OH:28])=[O:27]Compound 21 used in the preparation of compound 24 was prepared as follows. Sodium dichromate dihydrate (151 gm) was added to glacial acetic acid (575 ml) followed by 2-bromo-4-nitro-toluene (49.7 gm). To this solution was added dropwise sulphuric acid (175 ml) at such a rate to maintain the temperature between. 75-85° C. This mixture was heated to 100-110° C. for 3 h cooled to 50° C. and poured onto ice (1 litre). The aqueous phase was extracted with ethyl acetate, the organic layer back extracted with Aqueous sodium hydroxide solution and the resulting basic aqueous layer acidified with concentrated hydrochloric acid. The precipitated solid was filtered, washed with water and air dried to give 15.72 gm (28%) of 2-bromo-4-nitro-benzoic acid (compound 26) as a white solid.
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