C[N:2]([CH2:4][CH2:5][C:6]1[C:14]2[C:9](=[CH:10][CH:11]=[C:12]([CH2:15][C@H:16]3[CH2:20][O:19][C:18](=[O:21])[NH:17]3)[CH:13]=2)[NH:8][CH:7]=1)C>C(Cl)(Cl)Cl>[C:4]([CH2:5][C:6]1[C:14]2[C:9](=[CH:10][CH:11]=[C:12]([CH2:15][C@H:16]3[CH2:20][O:19][C:18](=[O:21])[NH:17]3)[CH:13]=2)[NH:8][CH:7]=1)#[N:2]A solution of the product from step (b) (2.5 g) and polyphosphate ester (20.0 g) in chloroform (40 ml) was refluxed for 20 minutes. Ice was added to the cooled mixture and the chloroform evaporated in vacuo. The remaining aqueous phase was extracted with ethyl acetate and the combined extracts evaporated in vacuo to give the desired product as a pale yellow oil (1.8 g).
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