A solution of 2.01 g (9.95 mmol) of diisopropyl azodicarboxylate (DIAD) in 5 ml of tetrahydrofuran is added dropwise, under an inert atmosphere, to a solution of 2.4 g (9.95 mmol) of [1-(1-isoquinolyl)-4-piperidyl]methanol, prepared in step 5.1, 2.87 g (10.94 mmol) of triphenylphosphine and 1.21 g (11.93 mmol) of 1,3-oxazolidine-2,4-dione in 40 ml of tetrahydrofuran, cooled to about −10° C., the temperature of the reaction medium being maintained throughout between −10° C. and 0° C. Stirring is then continued at 0° C. for 1 hour and then at 25° C. for 18 hours.
