The two-building Northbrook Court apartments at 3420-26 16th St. NW - constructed around 1918 by fabled Washington builder Harry Wardman - are being converted to condominium ownership. CBS Realty, which is handling sales for the owners, a partnership headed by physiologist Steven Laufer, said that 42 sales deposits have been made on one - and two-bedroom apartments. The units are priced from $47,000 to $94,000.The buildings are being substantially rehabilitated . . . In Los Angeles, Crocker National Bank has sold the 42-story Crocker Plaza building in the downtown financial district for $79 million in cash to Mitsui Fudosan (U.S.A.) Inc., a subsidiary of Mitsui Real Estate Development Co. of Tokyo. The purchase is the firm's first major investment in U.S. real estate.

While The Los Angeles Times reports that real estate shopping and sales are off by 25 percent in that gasoline-short area, there has been scant complaint thus far in this area by sellers of new houses. Although far-out subdivisions are expected to lose some traffic if gasoline continues in short supply here, there has been no dramatic turndown in buyer interest. Most shoppers tend to look for new dwellings within a few miles of where they already live . . . Appraiser Alfred Jarchow reports that prices of resold houses jumped about 3 1/2 percent in April in Montgomery County and that the level of prices for resold properties rose more than 7 percent in the first four months of this year. Jarchow says that the level of resale prices has doubled in the past 6 1/2 years.

Alfred Ekuban, who sold $6.5 million worth of real estate last year for the Shannon & Luchs real estate company, has opened his own brokerage firm in Takoma Park, at 6875 New Hampshire Ave. He has a staff of seven.