Real estate investment adviser Rubenstein Partners has purchased 600 Washington Blvd. in Stamford.

Constructed in 2009 to serve as the U.S. headquarters of the Royal Bank of Scotland, the 12-story, 450,000-square-foot trophy office building is one of the most recognizable in the Stamford market, sitting just off Interstate 95 and close by the Stamford MetroNorth station. At the time of the sale earlier this month, the building was 85 percent leased to several companies including NatWest Markets (formerly RBS, Corporate & Institutional Banking), UBS and Bank of America. NatWest Markets was the seller.

Rubenstein Partners said in a statement that it plans to convert underutilized areas within the building into additional “high quality” office space.

“We feel strongly that 600 Washington Blvd. offers an exceptional long-term investment opportunity,” Robert Andrews, a regional director with Rubenstein Partners, said in a statement. “This is an incredibly well-located office building with superior infrastructure and a high-quality tenant roster. We were able to leverage our familiarity with the market to secure and finalize the acquisition. Based on recent activity, Rubenstein Partners is also confident that Stamford is poised to strengthen in the coming years and we are pleased to add one of the premier office assets within the market to our growing portfolio.”

“We are pleased to have sold 600 Washington Blvd. to Rubenstein Partners and look forward to working with their team and continuing to be a proud and valuable member of the Stamford community,” Paul Stevelman, head of U.S., NatWest Markets, said in a statement. “Our 12-year lease term demonstrates our commitment to Stamford and we believe that remaining in this building best serves our employees and our clients. Our NatWest Markets US sales and trading operations that are based here, remain a core part of our business, providing our clients with access to the U.S. dollar markets across currencies, rates and financing.”

JLL represented NatWest in the transaction.