Brookfield Office Properties Inc. is poised to become the biggest office landlord in downtown Los Angeles, a long-sterile area that is beginning to see a rebirth from thousands of new apartments, a burst of hotel construction and even a burgeoning restaurant scene.

One problem: Despite the downtown's new energy in retail and residential, the office sector still is slumping.

Brookfield, one of the largest office owners in the U.S., is powering into Los Angeles by buying MPG Office Trust Inc. in a deal valued at about $2.1 billion, including debt. MPG, formerly Maguire Properties, owns four skyscrapers, including the KPMG Tower and Wells Fargo Tower.

The purchase amounts to a bet that the long-struggling downtown office market will turn around thanks to the larger evolution of the area, which has added 23,520 residents since 2006, according to the Downtown Center Business Improvement District, and new attractions including the L.A. Live entertainment center.

"We think downtown L.A. will follow where the rest of the U.S. is going," said Dennis Friedrich, Brookfield's chief executive, with "people living close to where they work."