Newton-based Senior Housing Properties Trust is set to purchase 27 medical office properties for $470 million.

The properties total 2.8 million square feet and are located in 12 states, according to a statement. The current average occupancy of the properties is 95 percent. The largest properties are two office towers totaling 331,000 square feet in Los Angeles.

The 27 properties are being purchased from Newton-based CommonWealth REIT, according to a statement. The sales are expected to be completed in a series of separate closings before June 30.