Air Condition repair

Tried to remove the Allen bolt clamping the high pressure pipe to the air condition compressor and failed miserably. According to the workshop manual it should be 23-27 Nm, but that exceeds my ability with a 190mm long 6mm Allen key. If anyone has managed to remove this pipe successfully please tell me how and with what.

Alec,Can you get an extension tube over the allen key for leverage?I took mine off complete with the compressor and then removed the pipes.