Hydrazine → 2-Amino-7-aminomethyl-6-(4-methoxy-benzyl)-4,5,6,7-tetrahydro-thieno[2,3-c]pyridine-3-carboxylic acid tert-butyl ester

In a 500 ml round-bottom flask, a suspension of 2-amino-7-(1,3-dioxo-1,3-dihydro-isoindol-2-ylmethyl)-6-(4-methoxy-benzyl)-4,5,6,7-tetrahydro-thieno[2,3-c]pyridine-3-carboxylic acid tert-butyl ester (5.00 g, 9.4 mmol) in absolute ethanol (200 ml) was flushed with nitrogen. The reaction mixture was stirred at room temperature and hydrazine (1.5 ml, 47.8 mmol) was added. The reaction mixture was heated to 80° C. for 6 hours and then cooled to room temperature. After 14 hours at room temperature, the precipitate was filtered off and washed with absolute ethanol. The mother liquid was concentrated in vacuo and the residue was dissolved in dichloromethane (75 ml) and refiltered to remove an additional precipitate. Concentration of the mother liquid afforded 3.2 g (85%) of 2-amino-7-aminomethyl-6-(4-methoxy-benzyl)-4,5,6,7-tetrahydro-thieno[2,3-c]pyridine-3-carboxylic acid tert-butyl ester as a solid.