Recent developments in commercial real estate in the Washington area:

* The Solar Building at 16th and K streets NW and a parking garage at 1602 K St. NW have been sold for more than $11 million to Sarz Properties N.V., a Netherlands Antilles corporation. The building contains 175,250 square feet of space and the garage 40,500 square feet.

* Georgetown Center (I) N.V. has purchased a six-story commercial building at 2121 Wisconsin Ave. NW for $9 million. The building contains 166,061 square feet of space.

* Nattak Development N.V. has purchased more than 72 acres of industrial property in Loudoun County for $1.6 million. The site is near Dulles International Airport.

* The accounting firm of Friedman and Fuller has expanded its offices by relocating to 11,000 square feet of space in the Dynamac Building, at 11140 Rockville Pike. The firm was previously in the Chevy Chase Lake Building at 8401 Connecticut Ave. Total value of the lease is $1.3 million.

* Olson Research Associates Inc., a research and consulting firm, has leased 11,000 square feet at Capital Office Park II in Greenbelt. The aggregate value of the lease is about $2 million. The facility is owned by Eleventh Springhill Lake Associates.

* NCR Corp. recently signed a lease at 1140 19th St. NW for its new office systems division.

* Vinnell Corp., a construction management firm based in California, has leased more than 25,000 square feet of space at the Flint Hill Office Park in Fairfax. The aggregate value of the lease is $1.8 million.

* At 4801 Massachusetts Ave. NW, a building owned by the Lenkin Co., the law firm of Kivitz & Liptz has leased about 3,100 square feet; the economic and pension plan consultants Stanley E. Clark Associates Inc. have leased 2,100 square feet, and the Foundation for Iranian Studies, 1,600 square feet.

* Executive View Inc., a company which provides phone-answering, typing and graphic services, has leased 532 square feet of space at 51 Monroe St. in Rockville.

* At the same location, Donahue, Ehrmantraut & Montedonico, a law firm specializing in medical malpractice defense, has leased 1,185 square feet of space.

* Cathedral Galleries has leased 950 square feet at 3301 New Mexico Ave. NW.

* A groundbreaking has been held for the Bellemead Development Corp.'s 270 Corporate Center, a 105,000-square-foot building on a site in Germantown.