N-benzyloxycarbonyl-m-fluoroanilinoacetaldehyde diethyl acetal (15 g) and 3,4-dihydroxyphenethylamine hydrochloride (5.75 g) were added to a mixture of n-butyl alcohol (150 ml) and water (20 ml) and then the mixture was refluxed for 11 hours in a stream of nitrogen. The reaction mixture was concentrated to dryness and the residue was in turn washed with ether and with a mixture of ether: ethyl acetate (2:1) and then crystallized with acetone. The crystals were collected by filtration to give 1-(N-benzyloxycarbonyl-m-fluoroanilinomethyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline hydrochloride (11.27 g), mp 184° to 186° C. (dec).
