BOSTON-Eighteen months after paying $660.6 million for it at auction, a partnership of Normandy Real Estate Partners and Five Mile Capital Partners is selling the iconic John Hancock Tower here to Boston Properties for $930 million. The purchase price includes the assumption of a $640.5-million senior mortgage loan.

In announcing its acquisition of the 1.7-million-square-foot Hancock tower, BXP says it’s also putting up $289.5 million in cash. The deal is expected to close by the end of the year.

The Normandy/Five Mile partnership reportedly was the sole bidder at the March 2009 auction on the Hancock tower, which at 62 stories is the region’s tallest building. Broadway Partners paid $1.3 billion for the office tower at 200 Clarendon St. in December 2006, part of a 10-building portfolio it acquired from locally based Beacon Capital Partners for $3.3 billion. Early last year, Broadway defaulted on about $700 million of debt in connection with the Hancock tower.

Cushman & Wakefield's Rob Griffin and Ed Maher brokered the transaction. Law firm Goodwin Procter LLP advised BXP, while Allen & Overy LLP and Haynes & Boone LLP advised the sellers.