A vote for Longwood

Beth Israel Deaconess Medical Center will lease half of a new laboratory research tower to be built by private developers next to its east campus in the Longwood Medical Area, paying a premium to keep its research in Boston and bypassing cheaper rents in Cambridge.

The deal enhances Longwood's status as a world-class -- and densely packed -- medical research center on the Boston side of the Charles River.

As the major tenant, Beth Israel will occupy seven floors of the 18-story Center for Life Science Boston building, or about 350,000 square feet. It is vacating research labs it now leases at the Harvard Institutes of Medicine a block away and moving all of its research scientists under one roof. The move will expand its total research footprint by about 40,000 square feet.

The developer, Lyme Properties LLC, plans to use the lure of the Beth Israel deal to entice biotechnology companies and big pharmaceutical firms into the other half of the 700,000-square-foot building, said Bob Green, chief operating officer for Lyme Properties. Lyme has already been in discussions with some of these companies, which want to be close to the hospitals and scientists where drug discoveries are being made, he said. Beth Israel is a clinical affiliate of Harvard Medical School.

''A lot of these firms were waiting to see the Beth Israel lease get signed," Green said. ''We think it is going to give us momentum in the leasing."

Beth Israel gets about $200 million a year in National Institutes of Health research funding, the third largest amount in the country among stand-alone hospitals.

The new glass and steel research building is expected to be complete by 2007. A second, slightly smaller building of 500,000 square feet is planned for a total combined potential investment of about $500 million and 1.2 million square feet of laboratory space, Green said.

The Boston Redevelopment Authority first approved the project in 2003. It pushes the city closer toward Mayor Thomas M. Menino's vision of building a strong scientific research cluster to complement Cambridge's groupings of scientific research companies on the other side of the Charles River.

''It says a lot about Boston. The greatest hospitals in the country are right here," Menino said in an interview yesterday.

Boston, especially Longwood, has been on a research roll lately.

Merck & Co. completed a lab complex next door to the new building's site last year. In 2003, Children's Hospital opened a 12-story research facility. Children's and the Joslin Diabetes Center are planning another nine-story research building. Harvard Medical School opened a research complex last fall with labs for 800 scientists.

Partners Healthcare System Inc., the nonprofit parent of Brigham and Women's Hospital and Massachusetts General Hospital, signed leases in 2003 for about 200,000 square feet of research space in Longwood.

In May, Partners started moving into 355,000 square feet at Charles River Plaza, next to the Mass. General campus. In all, according to recent disclosures made by Partners, the system has signed research leases for 1.6 million square feet, costing a total of $71 million in rents for 2005. All but 123,000 feet of that is in Boston, according to the disclosure statement.

Menino sat with Beth Israel chief executive Paul Levy yesterday during a groundbreaking ceremony under a tent on the future site of the new building. Levy said leasing new space in Boston, especially the Longwood Medical Area, is more expensive than leasing in Cambridge. But hospital executives decided Beth Israel's researchers should remain within walking distance of the hospital, where many treat patients.

''We made a clear business station to stay in Longwood and pay the premium," Levy said. He declined to say how much the new leases will cost, except to say they will be more expensive than its current leases at the Harvard Institutes of Medicine, which expire in 2008.

The area Lyme is developing was the former Blackfan Circle site of the Judge Baker Children's Center, which moved to Roxbury, combined with another lot with a parking garage that Beth Israel sold to the developers.

Christopher Rowland can be reached at crowland@globe.com.