A blockbuster real estate deal could transform a development company, Tishman Speyer Properties, a longtime titan in the local office space market, into a giant among owners of residential property in the city as well.

A partnership between Tishman Speyer and an investment bank, Lehman Brothers Holdings Inc., yesterday announced it had agreed to buy a real estate investment trust, Archstone-Smith, for $22.2 billion. The deal would add the Denver-based company ‘s 86,000 apartment units, which are spread throughout the country, to Tishman Speyer’s portfolio.

The deal comes just six months after Tishman dove into the Manhattan residential market with the acquisition of the 11,000-unit apartment complex at Stuyvesant Town and Peter Cooper Village for $5.4 billion, the biggest ever single-property residential purchase. Tishman Speyer is also said to be readying a bid to develop the West Side rail yards, a 26-acre space of which a large component could be residential.

Locally, Archstone owns more than 3,200 apartments in 10 buildings — most in Midtown — a portfolio of high-end rentals that it has gradually acquired since 2000. It claims to be the largest publicly-traded apartment owner in Manhattan, and paid more than $1.25 billion to buy the properties.

Tishman Speyer owns some of the city’s most notable office buildings, including the Chrysler Building and Rockefeller Center. Before announcing its new appetite for residential properties with the Stuyvesant Town deal, the company had owned only a few hundred apartments in the city.

“Once you make a commitment in residential, I’m guessing you probably think you’re better capable of managing the residential you have by expanding your portfolio,” the president of the Real Estate Board of New York, Steven Spinola, said.

A real estate attorney at LeBoeuf, Lamb, Greene & MacRae LLP, Stuart Saft, said the Archstone deal marks a growing interest in building expansive portfolios of real estate that are backed in part by financial giants, such as Lehman Brothers in the current deal.

“The bigger the package becomes — and this is a huge package — the more opportunities there are to avail themselves of some of the capital that is floating around the world looking for investment,” Mr. Saft said. “Up until the last few years, real estate was something a lot of people didn’t take a piece of.”

The giant deal builds on a growing number of blockbuster real estate transactions, including the Blackstone Group’s $39 billion February purchase of Equity Office Properties Trust, which beat out a bid by a New York-based REIT, Vornado Realty Trust.