According to Winthrop Realty Trust it has acquired a non-performing first mortgage loan secured by a 20-story, 514,000 s/f office building located at 1515 Market St. The loan, which is currently in maturity default, has an outstanding balance, exclusive of interest, default interest and late charges, of $70 million and was acquired for $56.85 million. Winthrop Realty Trust is a NYSE-listed real estate investment trust (REIT) headquartered in Boston.