To a suspension of trans-5,7-dichloro-2-methoxy-carbonyl-4-phenylmethylcarbonylamino-1,2,3,4-tetrahydroquinoline (3.11 g, 7.89 mmol) in a mixture of tetrahydrofuran (100 ml) and water (50 ml) was added aqueous lithium hydroxide (17.4 ml of a 0.5M solution, 8.70 mmol) and the resulting mixture was stirred at room temperture for 3 h. The organic solvent was removed in vacuo and the aqueous residue was acidified with concentrated hydrochloric acid and extracted with ethyl acetate (2×100 ml). The combined extracts were washed with saturated brine (1×100 ml), dried (MgSO4) and evaporated to give the crude product which was recrystallised from ethyl acetate/petroleum ether 60-80 to give the title compound as colourless crystals (2 crops, 2.65 g) identical in physical properties to example 34 step b.
