SL Green, which owns the most office buildings of any single company in New York City, plans to sell its 45 percent stake in the McGraw-Hill building on Sixth Avenue, between 48th and 49th streets, to Toronto-based Canada Pension Plan Investment Board for $576 million.

This is one of the biggest deals since the real estate downturn.

In transactions that sound like a Monopoly game, SL Green will use the proceeds from this sale to buy 125 Park Avenue, across the street from Grand Central (railroad) Terminal for $330 million from San Francisco investor Shorenstein Realty Services.