Real Estate investment trust Archstone-Smith said on Tuesday that it agreed to be acquired by a partnership between Tishman Speyer Properties LP and Lehman Brothers Holdings Inc. for about $22.2 billion, including debt and transaction costs.

The partnership will pay $60.75 a share in cash for the trust, representing a 22.7 percent premium to the firm's May 24 price, before shares rose on speculation of a buyout.

We have always been committed to maximizing value for our shareholders, and we believe this merger accomplishes that objective, offering a significant premium over the unaffected share price, said R. Scot Sellers, chairman and chief executive officer of Archstone.

Tishman Speyer, based in New York, is one of the country's largest real estate development companies, with office buildings and apartment properties on four continents.

The deal would give Tishner and Lehman more than 86,000 apartments in New York, San Francisco, Washington D.C, and Boston.

Archstone said its boards of trustees unanimously voted to approved the deal. Completion of the transaction is contingent on the approval by Archstone shareholders.

It is expected to conclude in the thirst quarter.

Shares of Archstone-Smith rose $4.92, or 8.9 percent, to close at $60.15 on the New York Stock Exchange.