The Duell family is selling a Manhattan portfolio of nine buildings, seeking around $300 million. The properties include two prominent retail buildings in Midtown: 5 East 57th Street, a 22-story, 49,000-square-foot building with a David Yurman store, and 673 Madison Avenue at the corner of 61st Street. The family is divesting as they shift away from real estate investments, capitalizing on increased demand for prized retail assets in Midtown. CBRE Group broker Darcy Stacom is representing the seller in the deal.