Diisopropylethylamine → 4-Guanidinomethyl-benzoic acid methyl ester dihydrate

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To a solution of methyl 4-(aminomethyl)benzoate hydrochloride (5 g) in dry ethanol (25 mL) was added 1H-pyrazole-1-carboxamidine hydrochloride (4.4 g) followed by DIPEA (13.0 mL) and the mixture was refluxed for 3 h. Ethanol was removed under vacuum. To the remaining viscous oil saturated solution of NaHCO3 (50 mL) was slowly added under vigorous stirring followed by addition of 300 ml water (resultant pH 9). A white solid is formed and stirring was continued for 1 h. This material was filtered off, washed with water (200 mL) and tert-butyl methyl ether (50 mL), and dried to give the title compound 24 as a white powder (4.7 g, 91%). 1H NMR (400 MHz, DMSO-d6) δ (ppm): 7.91 (d, J=8.0 Hz, 2H), 7.39 (d, J=8.0 Hz, 2H), 4.39 (s, 2H), 3.83 (s, 3H), 3.80-2.80 [m, 4H+2H2O (determined by elemental analysis]).

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