Sanctioned Russian billionaire Oleg Deripaska agreed to sell down his majority ownership in EN+ Group PLC, the U.K.-listed holding company that owns 48% of aluminum giant United Co. Rusal.

By distancing themselves from Mr. Deripaska, widely seen as an ally of Russian President Vladimir Putin, the move could help Rusal and EN+ to escape U.S. Treasury sanctions. Mr. Deripaska was among a handful of Russian tycoons, along with their corporate assets, targeted in the latest round of U.S. sanctions as the Trump administration escalates...