A multi-million-dollar transaction involving the purchase of the 50-year-old LaSalle Building in the heart of the downtown commercial area triggered speculation yesterday that the nex owners plan development of a luxury hotel combined with a multi-level urban shopping plaza and office space.

Purchasers T. N. (Ted) Lerner and Albert (Sonny) Abrmamson, who already are associated in developing four area shopping malls, would not comment on plans for the site, which includes several adjacent parcels.

Lerner said only that approximately 50,000 square feet at the southwest corner of Connecticut Avenue and L Street N.W. has been acquired in recently closed transactions. However, the land under the LaSalle office building is owned by a diverse group that had leased it to the LaSalle owner. Lerner indicated that a part of the transaction was a renegotiated land lease on a long-term basis.

Milton Ritzenberg, whose family has a history of development and construction here, and Donald Flamm of New York City sold the La Salle building to Lerner and Abramson after months of negotiations. No broker was involved.

However, the property - including the element of the land lease - had been available for approximately what would be about $250 a square foot if both land (the most important part of the package) and building were included. Such is the case in most transactions here.

The transaction also involved several pieces of adjacent property on L Street to make the total site large enough for a major new structure or major redevelopment. Some downtown real estate professionals expect a new of redeveloped building that might include a posh, multi-level shopping complex tied into a Madison-like hotel and office space combination. "It's a fantastic site," one non-involved realty pro said, adding that both Benwit Teller and I. Magnin are interested in having stores here.

The size of the site is one factor, but another is that it is located over a key Metro station in the citys highest-rent district. Additional factors are that the property has long been the site of a popular Scholl's cafeteria. Duke Zeibert's restaurant and (more recently) this city's only Brooks Brothers' clothing store on the second floor.