IJ= cN-thy of the dimethyl acetal and tert-butyl moiety of 19b employing CF&OOH (TFA)-HzO under an argon atmo-sphere afforded 4-[3-(2, 4-diaminopyrrolo [2, 3-d] pyrimidin-5-yl) propyllbenzoicacid (20b). Without isolation, the acid was coupled with diethyl L-glutamate in 84% yield using diethyl phosphorocyanidate (DEPC) 12 as a coupling reagent in anhydrous DMF. Basic hydrolysis of 21b with NaOH in THF-H20 at room temperature for 1 h followed ...