The carboxylic acid of choice (3-methoxyphenyl acetic acid, 0.055 mmol) and 0.055 mmol of HBTU were dissolved in 0.5 mL amine-free DMF. To this solution was added dropwise a solution of 4-Amino-3-(4-aminophenyl)furo[2,3-d]pyrimidine (9) in 0.5 mL DMF. The resulting solution was treated with 0.024 mL of N,N-diisopropylethylamine. The system was stirred at room temperature overnight and then was concentrated to dryness in a Speedvac system, reconstituted in 1 mL DMSO and purified by prep HPLC to give the title compound. MS(ES) m/e 375 [M+H]+.
