Rouse and Associates has purchased 21 acres in Beltsville, where construction has begun on Ammendale Technology Park, a 167,000-square-foot, three-building complex located at the corner of Baltimore Avenue and Ammendale Road.

The complex will include one office/research and development building containing 47,000 square feet, and two office/research and development/distribution buildings, each with 60,000 square feet. Occupancy is scheduled for late this summer.

Virginia Manor Corp. sold the property to Rouse and Associates for an undisclosed amount. The project architect is F. Daniel Cathers and Associates. Construction is by Norwood Industrial Construction Co.

Other recent developments in commercial realty in the Washington metropolitan area:

* The Prudential Insurance Co. of America reports it has acquired Tycon Courthouse, a 450,000-square-foot office building located at 8330 Old Courthouse Rd. in Tysons Corner. The building was purchased from Tycon Courthouse Limited Partnership for $66.5 million.

* Harvey Construction Co. announced the following projects: Construction of a $6 million, 12-story, 70,000-square-foot office building for Washington Development Group, at 1420 K St. NW; a $2 million, three-story, 15,000-square-foot retail building at 1229 Wisconsin Ave. NW; and a $1.6 million, three-story, 15,000-square-foot building to be occupied by Peoples' Drug Store, at 17th and P streets NW. Alan Lockman and Associates are the architects for the Washington Development Group project.

* Hersand Builders Inc. and A. G. Van Metre Associates Inc., in a joint venture, have leased office space in Kings Park at Burke Professional Center, located at the intersection of Braddock and Rolling roads in Burke. Van Metre will occupy a 15,000-square-foot building for its corporate headquarters, while the joint venture will lease the other two buildings, which contain 21,000 square feet and 5,700 square feet.

* Shannon and Luchs has announced the following commercial leasing activities: Checkered Flag of Virginia has leased 40,800 square feet at 302 East Annandale Rd., Falls Church. Systems Development Corp. has leased 14,808 square feet at 7925 Jones Bridge Dr., McLean.

* Cushman and Wakefield of D.C. has announced the following commercial leasing activities: Council of Americas has signed a lease for approximately 2,400 square feet of office space at 1625 K St. NW. Cullen and Dykman, a law firm, has signed a lease for approximately 3,508 square feet at 1225 19th St. NW.