[CH:1]([C:3]1[CH:4]=[C:5]([C:8]([OH:13])=[C:9]([O:11]C)[CH:10]=1)[C:6]#[N:7])=[O:2].B(Br)(Br)Br>ClCCl>[CH:1]([C:3]1[CH:4]=[C:5]([C:8]([OH:13])=[C:9]([OH:11])[CH:10]=1)[C:6]#[N:7])=[O:2]18 g of the product of Step A and 400 ml of dichloromethane were mixed together under nitrogen and the mixture was cooled to 0° C. 150 ml of a molar solution of boron tribromide in dichloromethane were added and the mixture stood for one night at ambient temperature. It was concentrated, cooled again to 0° C. and 250 ml of a normal solution of hydrochloric acid were added. The crystallized product was separated out, washed with water, dried then crystallized from an isopropanol--water mixture (1-2) to obtain 12 g of the expected product.
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