Mayor Bloomberg unveiled plans yesterday for a $700 million privately financed biotechnology center on the Lower East Side that, aides say, is a first step toward transforming the Big Apple into “the bioscience capital of the world.”

The city has selected a Pasadena, Calif.-based firm, Alexandria Real Estate Equities, to develop the 870,000-square-foot facility at the north edge of the Bellevue Hospital campus.

The deal appears to be a short-term sacrifice for the city’s Health and Hospitals Corporation, which manages Bellevue. The city will charge Alexandria $2 million in annual rent, but the firm’s first rent payment will not be due until 2009, when the second of the three buildings planned for the site is scheduled to be completed. But Mr. Bloomberg said the center will create 2,000 jobs and advance the city’s long-term strategy of “freeing New York from Wall Street’s boom-and-bust cycle.”

The city already trains 15% of the nation’s doctors, and its “genetic diversity” makes it an ideal place to conduct clinical drug trials, the president of the city’s Economic Development Corporation, Andrew Alper, said. But he added that biotech start-ups are leaving the city in droves. “It’s great that we have more patents than San Francisco and Boston combined, but without space, we don’t have jobs,” he said.

Meanwhile, Mr. Bloomberg told reporters yesterday that he has “given extensively to stem cell research” from his personal fortune, but a spokesman, Jonathan Werbell, declined to provide further details regarding the mayor’s donations. A Nobel laureate and president of the Memorial Sloan-Kettering Cancer Center, Harold Varmus, said that the city’s scientists sit atop a “$100 million treasure chest” of private money earmarked for stem cell research.