STAMFORD, CT-The $40 million senior mezzanine tranche acquired by Edison, NJ-based Mack-Cali Realty Corp. and Boston-based Winthrop Realty Trust in Connecticut’s central business district sold for approximately $250 to $275 per square foot, investors looking at the deal tell GlobeSt.com.

RFR Realty LLC, the Park Avenue landlord headed by Aby Rosen and Michael Fuchs, owns 1.67 million-square-foot, seven-building class A office portfolio, sources say. The complex—formerly owned by Equity Office Properties Trust—was sold off by the Blackstone Group after the private equity giant won a bid to take over EOP in 2007.

Blackstone tapped Manhattan-based Eastdil Secured to help sell the complex, and the Stamford portfolio subsequently was purchased by RFR for $850 million later that year. However, at syndication, the firm ended up having to buy of some of the more junior pieces of the debt once the market started to slide, sources say. Bank of America originated the deal, and as a defensive move over time, the bank started buying up pieces of their mezzanine debt.

With the two REITs now in the picture, the final maturity of the loan is August 2015, with the first maturity coming this summer. The question, sources say, will be whether the two companies will be able to extend the debt, depending on cash flow and leasing activity.

The local market, while strong, faces challenges. The Westchester-Southern Connecticut office market ended the fourth quarter with a class A availability rate of 25%, according to brokerage firm Studley.

But bright spots are beginning to pop-up. UBS AG renewed its lease and ruled out a move to 3 World Trade Center, Starwood Hotels will be moving to Harbor Point and NBC Sports Group will be relocating to a former Clairol factory in downtown Stamford.

The RFR portfolio consists of One, Two, Three and Four Stamford Plaza; 300 Atlantic St.; Canterbury Green; and 177 Broad St. Adam Spies and Nicholas Seidenberg of Eastdil Secured worked on securing the sale of the senior mezzanine debt.

UPDATE: In a statement following the publish of this article, RFR says the Mack-Cali/Winthrop purchase "represents a savvy investment" by two sophisticated investors, with a projected return of 12% based on the discounted purchase price.

"Indeed we ourselves recently closed on the purchase of additional $50 million mezzanine tranche, bringing our total to $250 million," the company says in an e-mail to GlobeSt.com. "We, like the Winthrop/Mack-Cali partnership, view these loans as opportunities to achieve excellent risk-adjusted returns."

Since acquiring the portfolio in 2007, occupancy at the site is 90%, and 2011 leasing velocity for the portfolio was more than double the competition, the company says. "As the leasing market recovers and economic fundamentals continue to improve we believe we will refinance the portfolio on or before the extended maturity date in 2014."