3-(1-Trityl-1H-imidazol-4-yl)propionic acid methyl ester (7.75 g, 19.5 mmol), J. Org. Chem. 2000, 65, 2229-2230, is dissolved in DCM (300 mL) and cooled to −78° C. To this is added a toluene solution of DIBAL (21.0 mL, 1.5 M). After 2 h MeOH (20 mL) is added followed by saturated aqueous Rochelle salt solution (50 mL). The mixture is partitioned between DCM and saturated aqueous Rochelle salt solution. The organic phase is dried (Na2SO4) and evaporated. The crude residue is purified via flash column chromatography (MeOH/DCM 1:99→MeOH/DCM 5:95) to give the aldehyde, 3-(1-trityl-1H-imidazol-4-yl)propionaldehyde as a yellow gum (cas #184030-88-4). 1H NMR (CDCl3) δ 9.83 (s, 1H), 7.38-7.31 (m, 10H), 7.16-7.12 (m, 6H), 6.58 (s, 1H), 2.90 (t, J=8.0 Hz, 2H), 2.83-2.79 (m, 2H).
