To a solution of 2,4-diamino-6-ethyl-5-(3-(2-(3-carboxypropoxy)phenoxy)propoxy)pyrimidine (0.3904 g, 1 mmol) and a catalytic amount of con. H2SO4 in EtOH (4 mL) was added triethyl orthoformate (2 mL) and the solution was left stirring at 25° C. for 8 hours. The reaction mixture was neutralized with K2CO3 and evaporated to dryness. The crude product was diluted with water and extracted with CH2Cl2. Evaporation to dryness gave the desired ester as white semi-solid (0.2720 g, 65%). 1H NMR (500 MHz, DMSO-d6): 0.99 (3H, t, J=7.5 Hz), 1.15 (3H, t, J=7.1 Hz), 1.93 (2H, m), 2.13 (2H, m), 2.33 (2H, q, J=7.5 Hz), 2.45 (2H, t, J=7.3 Hz), 3.78 (2H, t, J=6.0 Hz), 3.95 (2H, t, J=6.3 Hz), 4.03 (2H, q, J=7.1 Hz), 4.13 (2H, t, J=6.0 Hz), 5.54 (2H, s), 6.07 (2H, s), 6.87-6.90 (2H, m), 6.95-7.01 (2H, m).
