| abstract |
The invention relates to a process for the preparation of compounds of the formula I ##STR1## in which n is 1 or 2, R denotes hydrogen or an organic radical, R 1 denotes an organic radical, R 2 and R 3 are identical or different and denote hydrogen or an organic radical, and R 4 and R 5 , together with the atoms bearing them, form a monocyclic, bicyclic or tricyclic heterocyclic ring system having 5 to 15 carbon atoms, which process comprises reacting compounds of the formula II defined in the description with compounds of the formula IV defined in the description, in the presence of phosphinic anhydrides of the formula III, where appropriate eliminating radicals which have been introduced to protect other functional groups and, where appropriate, esterifying free carboxyl groups in a manner known per se. |