WASHINGTON, DC-Arnold & Porter LLP has inked a 20-year lease with Boston Properties for a new, mixed use development at 601 Massachusetts Ave., NW, in the city’s Penn Quarter. The law firm expects to take its 375,000-square feet leased space by October 2015.

The 11-story building will be developed on site acquired by Boston Properties from National Public Radio in 2008. It is being designed to LEED Gold standards and will include a retail component. It will be located at the intersection of Massachusetts Avenue, New York Avenue, and K Street.

Jennifer Perkins, a partner in the Arnold & Porter’s Real Estate practice group, advised the firm in the lease negotiations. CBRE’s Pat Marr, Sally Wilson and Timothy Dempsey represented Arnold & Porter as well. Jon Kaylor and Anne Dumont of Boston Properties represented the landlord/developer. A team from HOK led by Catherine Haley will provide interior design oversight for the project.

Law firms, next to the federal government, are the city’s bread and butter tenants, so it is hardly a surprise that a new development would be anchored by a tenant like Arnold & Porter. What is somewhat surprising is that the new building will not be located on the well-trodden — and once very narrow — path that top law firms favor in the District. This lease is indicative of tenants sacrificing top locations for more efficient space, Scott Homa, JLL research director tells GlobeSt.com.