For many New Yorkers, Midtown Manhattan, with its gleaming skyscrapers and busy transportation hubs, lacks an element of cool and cachet that its more culturally vibrant neighbors have. Hordes of office workers, commuters and tourists typically flood the area, leaving it feeling anything but residential.

What Midtown does have, though, is a glut of underutilized office buildings. Two in particular brought Nathan Berman, chief executive of Metro Loft Management, to the area: the hulking buildings of Pfizer’s former headquarters on East 42nd Street near Grand Central Terminal. Metro Loft, along with David Werner Real Estate, is converting the buildings into about 1,600 rental apartments.

Once completed, the project would be the largest office-to-apartment conversion nationwide, Mr. Berman said. The first tenants are expected to move in at the end of next year.

The developers also recently bought an office building around the corner from the Pfizer site to create roughly 450 residences, 25 percent of which will be affordable housing.

“We go where there is opportunity to convert what we believe to be undervalued assets, and we can do that anywhere in Manhattan,” Mr. Berman added. “Right now, Midtown seems to be presenting the most opportunities for us.”