maybe you should do some real research about the drug you are looking for...because you cannot extract DOB from a plant..its a synthetic drug..and this forum is not about synthesizing drugs..
but here is the synthesis..if you can follow it
SYNTHESIS: To a well-stirred solution of 1.95 g of the free base of 2,5-dimethoxyamphetamine (2,5-DMA) in 12 mL glacial acetic acid, there was added 1.8 g elemental bromine dissolved in 4 mL acetic acid over the course of 5 min. The slightly exothermic reaction was allowed to stir for 3 h, and then added to about 200 mL H2O. The cloudy solution was washed with 2x100 Et2O, made basic with aqueous NaOH, and extracted with 3x100 mL CH2Cl2. Evaporation of the solvent from the pooled extracts gave about 3 mL of a pale amber oil which was dissolved in 250 mL anhydrous Et2O and saturated with anhydrous HCl gas. The fine white crystals of 2,5-dimethoxy-4-bromoamphetamine hydrochloride, DOB, were removed by filtration, Et2O washed, and air dried. These weighed 1.7 g and had a mp of 195-196 °C. Recrystallization from IPA brought this up to 207-208 °C. Proton NMR spectroscopy of the hydrochloride salt in D2O gave confidence that the bromine atom had uniquely entered the 4-position, in that there were only two unsplit aromatic hydrogen atoms present, at 6.97 and at 7.20 ppm downfield from external TMS. -PIHKAL
go to erowid and read about it..