Boston-based Synergy Investments and California-based DivcoWest have purchased an office building in downtown Boston for $48 million.

The 125,000-square-foot property is located at 55 Summer St.

The purchase is the fifth building the partners have acquired in the downtown area in recent months.  Last month, DivcoWest and Synergy closed on 38 Chauncy St., a 152,000 square foot office building, and earlier this summer purchased 71, 77 and 87 Summer St., a three-building portfolio totaling approximately 90,000 square feet.