Roman Blanco, CEO of Santander USA, has purchased a brownstone at 407 Beacon St. for $4.3 million.

Santander re-branded its U.S. branches just this week, with more than 700 former Sovereign Bank locations adopting the name of the company’s Spanish parent. Worldwide, Santander has more than 14,000 branches and $1.3 trillion in assets, and is one of the largest banks in Europe and Latin America. The Sovereign re-branding will kick off a major push for the bank into the American market, including a $200 million advertising campaign.

Before being appointed to lead Santander’s U.S. expansion, Blanco was the head of the bank’s Colombian and Puerto Rican subsidiaries.

His new six-bedroom, 5,391-square-foot pied-à-terre in the Back Bay features its own patio, an au pair suite and working fireplaces. The listing agent was Cheryl Marsh of Marsh Properties.