"Disabling" the ignition system
The control unit or the electronic switch of the ignition coil will definitely be damaged if the engine is turned with the starter while the high-voltage cable is removed. Therefore:
Models with 4- and 5-cylinder engines: With the ignition off, disconnect the electronic switch plug (next to the ignition coil).
Models with 6-cylinder engine: With the ignition off, disconnect both plugs of the electronic switch (on the rear wall of the engine compartment).
[Information obtained from this resource: AudiManual]