The University of Southern California is enlarging its operations in Washington with the acquisition of a 60,000-square-foot building near Dupont Circle that will be home to a new D.C. campus. The $49.4 million purchase of the property at 1771 N St. NW, announced Wednesday, enables the private university in Los Angeles to establish an eastern hub for teaching, research, lobbying, recruiting, alumni networking and community outreach. The deal underscores that higher education institutions based elsewhere often find it desirable to establish a prominent Washington address.