Embattled real estate developer Harry Macklowe has signed a contract to buy a famous Upper East Side rental apartment building that is home to several prominent New Yorkers — including legendary apartment-sale broker Alice Mason — and convert it to condominiums, The Post has learned.

Macklowe, trying to rebound from the recent loss of much of his empire, plans to spend $70 million to purchase of 150 E. 72nd St. at Lexington Avenue. The condo conversion could be an interesting ride for all concerned. To make a profit, Macklowe will need to persuade rental tenants to buy their apartments or move out so he can resell them at market prices.

Macklowe is seeking joint-venture partners for what’s expected to be a total $110 million project including renovations and a new penthouse to be constructed on the roof.

The elegant 12-story building has just 34 jumbo apartments, some of which are rent-stabilized or rent-controlled with rents far below market value.

Mason, whose home is rent-stabilized, has been one of the most prominent dealmakers for the city’s luxury apartments for 40 years. She pays just over $2,000 a month for an 8-room, 2,000 square-foot unit.