Boston Properties acquired the 719,000-sf office tower in 1997 and embarked on extensive capital improvements and retenanting of the property. The 875 Third Ave. sale follows closely on another major disposition by the REIT. Last month, Boston Properties completed the sale of One and Two Independence Square in Washington, DC in a $345-million deal.

The two transactions are part of what Boston Properties' officials say is an ongoing strategy of selling off assets in order to secure leverage-neutral permanent financing for 399 Park Ave. The company spent roughly $1 billion for the 1.68-million sf building in a deal that closed in late summer.

"The sale of 875 Third Avenue illustrates our ability to create and realize value through the sale of one of our premier properties," says Mortimer B. Zuckerman, chairman of Boston Properties.