GFP Real Estate secured five lease transactions totaling 18,124 square feet at 515 Madison Ave., the DuMont Building, in Manhattan’s Plaza District. Martin McGrath of GFP Real Estate and William Grover of Newmark represented ownership in all five transactions. They include the following:  

• Investment firm Blackbern Partners signed a three-year lease renewal for 2,956 square feet. Cooper Weisman and Scott Gutnick of Newmark represented the tenant.

• Boyd, Boyd, Boyd, P.C., a four-generation-run family dentist office, signed a 15-year lease extension and expansion for 7,098 square feet of medical and administrative office space. Ted Andrews of Andrews Real Estate Advisors represented the tenant.  

• Lefko Properties, a New York City-based real estate investment firm, signed a new three-year lease for 1,828 square feet of office space, represented by Tony Builder of Bradford Allen.  

• Wells Hill Partners, a private investment banking and advisory firm, signed a new eight-year lease for 3,956 square feet of general and executive office space, represented by Jonathan Franzel and Claire Koepel of Newmark.  

• Xianglong Li DDS, provider of general & cosmetic dental care, signed a new 15-year lease for 2,286 square feet of medical and office space, represented by Sam Matayev of Norman Bobrow & Company Inc.