The 22-year-old will now attempt to revive his career in Lyon and Aulas has explained how much his club are set to pay and when they hope to complete the deal.
"For the moment, we are in agreement in principle but we still need to write the contract up, which is a bit complicated because there are a fair amount of bonuses,” he told RMC Sport.
“It was big operation, because it will be worth around €16.5m [£14.3m] plus €8m [£6.9m] in bonuses.
"This is a big investment. Manchester United bought him from PSV for €34m plus €8m.
"I believe that a certain amount of the bonuses are due to PSV following a transfer. There is a whole load of literature to be written and that is what is happening between both clubs at the moment.
"But we are used to working with Manchester United, they are a very structured club who, generally, stick to their word.
"We worked with them for the arrival of Rafael, a little while earlier. It is in progress, but I think it will require another 48 hours for him to be registered.”
Aulas also says that Memphis is the perfect signing for the French club and can bring flair to a side that is currently fourth in the table.
“It was a dream, because he corresponds exactly with the player we were looking for. In addition, he has a certain panache,” he added
"It is true that Jose Mourinho did not play him that much, so there was an opportunity that we took when we negotiated with the representatives of Manchester United.”