San Francisco developer DivcoWest and Boston-based Synergy Investments have completed the purchase of 38 Chauncy St. in downtown Boston for $39.5 million.

New York-based developer Brickman, a private equity real estate company, acquired the 132,000-square-foot office building in 2011 for $21 million. Since then, the occupancy rate has risen from 50 to 80 percent, according to Brickman’s web site.

DivcoWest and Synergy have been investing heavily in Boston office space in recent months. In June, they acquired the 90,000-square-foot portfolio at 71, 77 and 87 Summer St. in Boston for $31.5 million, after acquiring three buildings in the Seaport district last year.