52.07 g of iodine, in solution in 250 cm3 of tetrahydrofuran, were added dropwise to a solution of 37.75 g of methyl(3aRS,4SR,7aRS)-2-benzyl-7-hydrazono-4-phenyloctahydroisoindole-3a-carboxylate in 200 cm3 of tetrahydrofuran and 43 cm3 of triethylamine. Stirring was maintained at room temperature for one hour after the end of the addition. 1 dm3 of water and 1 dm3 of ethyl acetate were then added. The organic phase was separated by settling, washed successively with a saturated sodium hydrosulphite solution and then with a saturated sodium chloride solution, and dried over magnesium sulphate. After concentrating the solvent under reduced pressure, the residue was purified by flash chromatography on silica gel (230-400 mesh), elution being carried out with a mixture of cyclohexane and of ethyl acetate (95/5 by volume). 22.25 g (47%) of methyl(3aRS,4SR,7aRS)-2-benzyl-7-iodo-4-phenyl-2,3,3a,4, 5 ,7a-hexahydro-1H-isoindole-3a-carboxylate were thus obtained in the form of a yellow pasty solid, the characteristics of which were as follows:
