Much of downtown Washington's current new-office leasing -- which in recent years reached unprecedented levels at 2.5 million square feet annually -- now is taking place in a rejuvenated corridor along Vermont Avenue NW.

More than 1.3 million square feet of space is scheduled to be completed within the next three years in five buildings in this section near Thomas Circle crisscrossed by Vermont and Massachusetts avenues and bordered by K, N, 13th and 15th streets NW. Therein lies evidence that new downtown office developement is finally moving east of 15th Street after going west almost to Georgetown in the 1970s.

In addition, three buildings with 200,000 square feet of space are being refurbished in the area. There also is a good prospect of a 1981 start on a $40 million hotel by Hilton International.

These are some of the highlights in the rejuvenation, upgrading and rebuilding of the area south and west of Thomas Circle to McPherson Square.

In the late 1970s, this area was the site of several declining office buildings, an over-age hotel and an exotic bar -- and little else.

Because a new Hilton is scheduled to be built on a site just behind the Madison Hotel and its adjacent office building, the emergence of the Vermont corridor recalls the remarkable development foresight activated in the 1960s by Marshall Coyne. He built the Madison buildings in what was to become the first major step in the rejuvenation of 15th Street north of K.

Newly open at 1110 Vermont Ave. NW, the New-York-based Stillman Group's 250,000-square-foot office building is reported 50 percent leased by Barnes, Morris & Pardoe. Tenants include Computer Sciences Corp., Ziff-Davis Publishing and the Helicopter Association. Leases are in the $18-20 range per square foot. Upper floors are still available along with retail space on the first level.

Next door at 1120 Vermont, the Washington-based Sylvan Herman group is completing an even larger structure (450,000 square feet) scheduled for April occupancy. Leasing professionals are buzzing that Riggs National Bank may take 300,000 feet for its operations division. But an executive of Shannon & Luchs, the agent, said the contract has not yet been signed.

Just north of the 1120 building, Prudential Life Insurance plans a 250,000-foot building to be called One Thomas Circle. Next door, on M, will be the new Hilton.

On the east side of Vermont, with corners on L and 14th, the American Medical Association is building a 170,000-foot building that will be its local headquarters and also have space for other tenants. On the southwest corner of Vermont and L streets, the John Akridge Co. is completing a 160,000-foot structure leased for winter occupancy.

Peter Speier, Washington director and senior vice president of Julien J.

Studley Inc., which is preleasing One Thomas, said that through 1963, some 6.2 million square feet of new space is scheduled in downtown, with only 4.1 million square feet still unleased. "One million feet of that unleased space is in a pending-lease stage. That makes the Vermont corridor attractive in a market that may not meet demand unless activity slows considerably."

The eastward move of new commercial office space was pinpointed earlier this year by James O'Brien, Coldwell Banker's Washington director for commercial services. He predicted a rebuilding-rejuvenation of a "new downtown in the old downtown in the 1980s," citing the new convention center, Metro service and Pennsylvania Avenue redevelopment as contributing factors. m