A real estate fund sponsored by CBRE Global Investors has acquired 100 High St. in downtown Boston, part of a portfolio of trophy Boston and Cambridge office buildings that Blackstone’s Equity Office division is unloading this fall.

The purchase price for 100 High St. was approximately $380 million, according to a source familiar with the transaction.

The 28-story tower contains 546,336 square feet of office space and is 64-percent leased, with large blocks of available space on the lower floors. The acquisition also includes a 273-space underground parking garage.

In addition to 100 High St., Blackstone is selling 125 Summer St., 60 State St., 225 Franklin St. in Boston and One Memorial Drive in Cambridge. The combined purchase price has been reported to be $2.1 billion.

Los Angeles-based CBRE Global Investors said it plans to "invest heavily" in 100 High St. with upgrades to building systems and adding conference facilities and outdoor meeting space.

"Boston, which is in the midst of a robust recovery, is one of the nation’s strongest Gateway office markets," Vance Maddocks, president of CBRE Strategic Partners U.S., said in a statement. "Changing workforce demographics are fueling urbanization and driving leasing velocity in the Financial District."

Investors are showing renewed interest in high-profile downtown Boston office properties this fall, with Norges Bank Investment Management agreeing this month to acquire a 45-percent interest in the 791,000-square-foot Atlantic Wharf and the 1.3-million-square-foot 100 Federal St. from owner Boston Properties. That deal, which includes 601 Lexington Ave. in New York City, is valued at $1.5 billion.