the reaction the solution was filtered to remove insolubles and filtrate was collected the residue was dissolved in 200 ml dichloromethane and washed with 5 na 2 co 3 3 u00d7 100 ml the organic layer was collected and dried using anhydrous sodium sulfate after filtration the organic layer was concentrated using a rotoevaporator to yield an off white crude product compound 4 following evaporation of the solvent the product was washed with diethyl ether and dried in vacuum the compound 4 was further purified by recrystallizing from benzene in the next step the boc protecting group was removed by treating with trifluoroacetic acid which occurs within minutes compound 4 1 5 gm 3 18 mmol was dissolved in 10 ml dichloromethane and cooled to 0 u00b0 c to this solution was added a mixture of trifluoroacetic acid 10 ml and dichloromethane 20 ml drop wise over a period of 30 min under inert atmosphere after the addition the reaction mixture was brought to room temperature and stirred for another 2 hours the reaction mixture then was concentrated using a rotoevaporator to obtain a slightly yellow viscous liquid this solution was diluted with 75 ml of water and the ph was adjusted with enough 1 m sodium hydroxide solution to bring the ph of the solution to 10 and then extracted with 20 ml of.