The Mount Vernon Co. has purchased a 46,000-square-foot Boston office building located at 434 Massachusetts Ave. for $4 million.

The building, in Boston’s South End neighborhood, is the combination of four separate brownstones and features an outdoor courtyard, according to a statement. The Mount Vernon Co. plans to upgrade the building.

"We are very excited about upgrading this property and to become a part of the South End business community," said Bruce A. Percelay, chairman of The Mount Vernon Co.

"The Mount Vernon Co. was the ideal buyer for this building given both its reputation as a quality landlord and its history of involvement in the community," said Ron Geddes, senior associate at Gibson Sotheby’s International Realty, who brokered the sale. "This building serves an important need in the South End and having The Mount Vernon Co. at the helm is a win for all concerned."