A subsidiary of BlackRock Realty Advisors of New York has purchased a 136-unit apartment building in Boston’s South End neighborhood for $53.5 million.

The apartment complex at 45 E. Newton St. was sold by its developer, a joint venture of RF Walsh Co., Kenney Development and National Real Estate Advisors.

The property opened in 2006 and is 99 percent occupied with residents, according to information from CBRE/New England, which brokered the deal. Since its opening, the apartments have consistently been more than 90 percent occupied, said Biria St. John, executive vice president with CBRE. 

"It’s really benefited from the proximity to Boston Medical Center and the BU Dental School," he offered. "The market is very healthy for apartment assets from the investment perspective … and for the rental fundamentals. There are so few opportunities in the South End to acquire and develop assets like this."

The seven-story James Court apartments are located on the grounds of the original Boston College High School. One-bedroom apartments range from $2,300 to 2,700 per month; two-bedroom units lease for between $3,200 and $3,700.

The buyer has retained Fulton Properties, a subsidiary of Kenney Development Inc., to continue to oversee the leasing and management of the property.