Webb/Sequoia Inc. of Fairfax, a partnership between the Sequoia Building Corp. of Fairfax and the Webb Cos. of Lexington, Ky., has announced the acquisition of Dulles Corner, a 48-acre site adjacent to Washington Dulles International Airport.

The master plan for the project, which is situated at the corner of Route 28 and the Dulles Access Road in Fairfax, calls for eight buildings of between eight and 12 stories, and totaling 1.5 million square feet of space.

The buildings will be in a six-acre office and hotel park, which will house major corporations, restaurants, banks, cafeterias, and a travel agency. A luxury Hyatt Hotel, with 317 rooms and 230,000 square feet of space, will include a restaurant and conference facilities.

Dulles Corner Associates is the project's developer. The architect is David Habib of WZMH Group Inc. of Dallas, and Cushman & Wakefield are leasing agents.

Construction is scheduled to begin before the end of the year, with first occupancy expected by fall of 1986. The total projected value of Dulles Corner is $200 million.

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

*Stanley Martin Cos. Inc. has purchased and is currently renovating the W. J. Sloane Building at 7220 Wisconsin Ave. in Bethesda.

The company plans to lease the entire 50,000-square-foot building through SMC Real Estate, its in-house leasing division. Minor renovations are planned for the building's exterior.

*Baier Properties Inc. said it has acquired a 5.13-acre parcel of land in the I-495/Route 50 area of Fairfax.

The company plans to build two six-story office buildings totaling 225,000 square feet. Construction is scheduled to begin this spring.

*Coldwell Banker announced the following transactions: Spectet Ltd., investors, has purchased 3.66 acres in Reston from Reston Land for $1.04 million, and Oxford Development, a construction firm, has leased 12,932 square feet of office space at 7315 Wisconsin Ave., Bethesda, from Bethesda Air Rights.

*Hannover Healthcare Inc., a health management firm, has leased 12,000 square feet of space at 20251 Century Blvd. in Germantown.