The invention relates to an improved process for the synthesis of (3S,4S)-tetrahydrofuran-3-yl 4-isopropyl-6,7-dihydro-3H-imidazo[4,5-c]pyridine-5(4H)-carboxylate, and pharmaceutically acceptable salts thereof, such as the methanesulphonic acid salt.本發明係關於合成(3S,4S)-四氫呋喃-3-基4-異丙基-6,7-二氫-3H-咪唑并[4,5-c]吡啶-5(4H)-羧酸酯,及其醫藥上可接受之鹽,例如甲磺酸鹽之改良方法。