A solution of methyl 4-(6-aminobenzimidazol-1-ylmethyl)-3-methoxybenzoate (J) (0.63 g.) and 2,6-lutidine (0.36 ml.) in dichloromethane (10 ml.) was treated with cyclopentyl chloroformate (0.33 g.). After stirring for 24 hours the solution was diluted with dichloromethane. The mixture was washed successively with 20% w/v sodium hydroxide, water, and brine, then dried (MgSO4) and evaporated. The resultant residue was purified by flash chromatography on a 6×20 cm. silica gel column using 1:3 v/v hexane:ethyl acetate as the eluent to give the title compound (0.57 g., 93%); NMR: 1.7[m,8H, (CH2)4 ], 3.8(s,3H, OCH3), 3.9(s,3H, OCH3) 5.2(m, 1H, CHO), 6.17-7.0(br m,3H), 7.5-7.8(br m,4H).
