| http://www.w3.org/ns/prov#value | - des: ##STR17## or their cyclic anhydrides of the formula: ##STR18## or else the corresponding asymmetric diesters:As already mentioned in the disclosure of the first group of methods according to the invention, the acylation reaction is carried out in anhydrous conditions, into organic solvents such as THF or CH.sub.2 Cl.sub.2 and under nitrogen andemploying as a catalist an organic base, preferab
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