The Historic Districts Council plans to unveil Tuesday a list of 33 midtown east buildings that it believes are worthy of protection. The Manhattan-based advocacy organization for the city’s historic districts plans to submit its list to the city’s Landmarks Preservation Commission ahead of a likely rezoning designed to spur development of a new generation of bigger and taller, state-of-the-art buildings in the area. The list was pared down from an original pool of 78 significant buildings that stand within the proposed rezoning area. The final roster includes 20 commercial buildings, including eight pre-war and 12 post-war; six hotels; four institutional buildings; and three residential buildings. They range from the Minnie Young residence on East 54th Street, to the old Union Carbide building at 270 Park Ave. and the Yale Club on Vanderbilt Avenue. In arriving at the final 33 properties, the organization prioritized those that it deemed the most architecturally significant, as well as the most threatened by the proposed rezoning, meaning the ones that would be considered “underbuilt,” or significantly smaller than what would be allowed under the proposed new regulations. “In that instance there is a much higher level of threat to the continued existence of the building,” said Simeon Bankoff, executive director of the Historic Districts Council. Mr. Bankoff pointed out that if those buildings were landmarked, they would still have “a lot of transferable air rights you could add to the pot that is part of the continued rezoning.” The problem is that those rights are often not easily transferable, according to Steven Spinola, president of the Real Estate Brokers of New York. Currently, land owners in midtown east can sell air rights only to buildings adjacent, or across the street. This limits the options for those who own landmarked buildings and thus far the midtown rezoning plan has included no provisions that would create more flexible rules. Mr. Spinola also said that buildings should not be given landmark status just because their zoning might change and that that status should be reserved for truly notable buildings. “There may be some that are worthy of designation,” he said. “But it’s funny that a lot of these sites also happen to correspond to the sites that could take advantage of the rezoning and create wonderful new office towers.” How many of the 33 buildings the Landmarks Preservation Commission ultimately decides to review for possible landmark status remains to be seen. “We have been evaluating buildings within the East Midtown study area for their potential eligibility for landmark designation, and the buildings in the requests from HDC and other advocacy groups are part of that review,” a commission spokeswoman said.