Drawing national attention to the local campaign to stop Northwestern University from tearing down old Prentice Women's Hospital, the National Trust for Historic Preservation on Wednesday will name the concrete, clover-leaf shaped Chicago high-rise to its list of America's 11 Most Endangered Historic Places. The trust, a non-profit based in Washington, D.C., issues the list each year to help save buildings and other sites it deems significant. While the list carries no legal authority, it has proved to be a potent device for galvanizing public support. Since its debut in 1988, only eight of the 233 featured sites have been destroyed, Stephanie Meeks, the trust's president, said in an interview Tuesday. There is real urgency in the trust's support for old Prentice. Northwestern had been preparing to request a demolition permit for the structure, which it wants to tear down to make way for an as-yet unfunded medical research tower. The university only agreed to hold off on June 2 when the Commission on Chicago Landmarks, at the university's request, deferred a hearing on preliminary landmark designation for the building.