the 7-bromo derivatives (5a and 6a) were synthesised and their acidhydrolysis (l :.l dioxane/water) and trichloroacetolysis in benzene were studied and compared with those of the unsubstituted compounds (5b and 6b). Contrary to expectations based on the results obtained with the epoxides of type 2 and 3, the introduction of the substituent on the aromatic moiety, in particular the strong electron-donating