Photo courtesy of Synergy

Boston-based developer Synergy expanded its downtown portfolio with a high-rise office building, 265 Franklin St., in what could be the first in a series of acquisitions with a new financial partner.

The $116 million transaction is a joint venture with Axonic Capital of New York. The seller was Boston-based Clarendon Group USA.

Spanning 358,406 rental square feet, the 21-story tower previously traded for $170 million in 2006. It is currently assessed at $137 million, down from nearly $175 million in 2023.

In an announcement, Synergy said it will continue to partner with the alternative investment manager Axonic Capital on “high-quality real estate opportunities.”

“265 Franklin St. is an exceptional asset located at one of the most important intersections in downtown Boston,” Synergy CEO David Greaney said in a statement. “Its institutional-quality construction, flexible floor plates, extensive recent capital improvements, and premier location create a compelling opportunity to continue enhancing the tenant experience while benefiting from the ongoing recovery and evolution of Boston’s office market.”

Allianz Life Insurance provided $116 million in mortgage financing. 265 Franklin St. previously received $150 million in mortgage financing from Fireman’s Fund Insurance in October 2020.

The property is losing a major tenant later this year in law firm McCarter & English, which is relocating across the street to Chiofaro Company’s International Place.

The 27-tenant roster also includes Ares Management, White Mountains, Cerity Partners, Greater Boston Chamber of Commerce and Rhumbline Advisers.

The previous ownership invested $18.6 million in the base building and $26.5 million in tenant amenities, Synergy said.

Synergy’s recent Boston acquisitions include 101 Merrimac St., 101 Arch St. and 179 Lincoln St.