2-Chlorotrityl chloride resin (2.3 g, 3.0 mmol) was swelled in DCM for 20 mins and filtered. Dimethylmalonic acid (2 eq; 6.0 mmol; 793 mg) was dissolved i DCM:DMF 1:1 (10 mL) and added to the resin followed by DIPEA (6 eq; 18.0 mmol; 3.14 mL) and DCM (10 mL). The resin was shaken overnight at RT. The resin was filtered and washed with DCM:MeOH:DIPEA (17:2:1), DCM, NMP og DCM (2×25 mL of each). The resin was swelled in DMF for 20 mins and filtered. HOAt (3 eq; 9.0 mmol; 1.23 g), DIC (3 eq; 9.0 mmol; 1.40 mL) and DMF (25 mL) was added and the resin was shaken for 90 min at RT. The resin was filtrered and 3-(1-Trityl-1H-imidazol-4-yl)-propyl amine (1.8 eq; 5.40 mmol; 1.84 g), DIPEA (4 eq; 6.0 mmol; 2.09 mL), and DMF (10 mL) was added. The resin was shaken for 2 days. The resin was filtered and washed with NMP (5×20 mL) and DCM (10×20 mL). 2,2,2-Trifluoroethanol/dichlormethan 1:1 (20 mL) was added to the resin and it was shaked for 2 hrs. The resin was washed with 2,2,2-Trifluoroethanol/dichlormethan 1:1 (10 mL) and the combined filtrates were collected and concentrated in vacuo to yield the title compound.
