Richards Associates Inc., a Washington development firm, has unveiled plans to erect a 60,000-square-foot wholesale distribution building in Capital City Market, near the junction of Florida and New York avenues in the District.

It would be the first new distribution warehouse constructed in the market in 30 years, according to the firm's president, Judith W. Richards.

Construction of the building, which will be located at 300 Morse St. NE, will begin in February, Richards said. Richards Associates is developing the warehouse for Sun Development Corp., an investment group. Devrouax & Purnell are the architects.

The building will sit on an eight-acre site bought by the D.C. government in March 1983 as part of an effort to modernize the market. The land will be leased to Sun Development Corp. on a long-term basis, Richards said.

Twenty-eight percent of the warehouse already is leased to Sam Wang Food Corp., a Korean-owned wholesale company.

Richards said she expects the rest to be leased quickly, even though food wholesalers have been moving out of the District because of the market's deterioration.

Other developments in commercial realty in the metropolitan area:

Quadrangle Development Corp. has announced the following new tenants at National Place, a $150 million development at 1331 Pennsylvania Ave. NW. that houses 410,000 square feet of office space, the J. W. Marriott Hotel, and a retail mall managed by the Rouse Co.:

Buchman, Buchman & O'Brien, a law firm specializing in alcoholic beverages, tobacco and firearms issues, has leased 2,581 square feet on the seventh floor of the south tower. National Distillers & Chemical Corp. has leased 1,191 square feet, also on the seventh floor, for its Washington government-affairs office. Hiram Walker & Sons Inc. has leased 1,298 square feet on the seventh floor in the north tower, for its government-affairs office. The Association of Private Pension and Welfare Plans has leased 2,832 square feet on the seventh floor in the north tower. The Middle East Economic Digest, a weekly publication based in London, has leased 1,293 square feet on the 12th floor in the north tower.

* Psychological Services Inc. has signed a five-year lease from New York Life Insurance Co. for 2,945 square feet at 1333 H St. NW.

* The News Agency of Nigeria, the US-Asian News Service and the Committee in Defense of Life have leased office space at the National Press Building at 529 14th St. NW.

* Network Plus Corp. has signed a five-year lease from C.A.G. Associates for 1,216 square feet at 1019 19th St. NW.

* Safeway Stores has leased 33,750 square feet of industrial space at 4501-4517 S St., Beaver Heights, Md., from Murwall Co.

* Bethesda Air Rights has leased space at 7315 Wisconsin Ave. in Bethesda to the following organizations: Hyatt Hotels Corp.; International Trade and Tech Services; Groner and Groner; Berner, Lanphier & Associates, consultants; Benjamin Schlesing & Associates, consultants; Pike and Fisher; Booz-Allen and Hamilton, management and technology consultants; and Samuel H. Book, management consultants.

* AT&T Communications Inc. has leased 68,209 square feet of office space at 10800 Parkridge Blvd., Reston, from Walker & Co.

* Arabian American Oil Co. has leased 4,000 square feet at 1667 K St. NW from The John Akridge Co. for $700,000.