Under terms of the deal, Cogdell's common stockholders will receive $4.25 per share, valued at around $217 million, which represents an 8% premium over Cogdell's Dec. 23 closing stock price of $3.92. Cogdell's preferred stockholders will receive $25 per share, plus unpaid dividends when the deal closes in the second quarter.

Ventas, of Chicago, will fund the transaction through the assumption of Cogdell's $250 million mortgage debt and other borrowings. On Dec. 21, Ventas closed a $500 million unsecured term loan led by J.P. Morgan Securities LLC and Citigroup Global Markets Inc. The buyer expects its debt-to-Ebitda ratio to be around 5 times after the deal closes.

"Cogdell's high-quality properties enhance our medical office building market presence, especially in the southeast, and provide an opportunity to scale our Lillibridge Healthcare Services subsidiary platform," Ventas chairman and CEO Debra Cafaro said in a statement.

With the acquisition, Ventas gains Cogdell's 72 medical office buildings, including two still in development; the properties have a total of more than 20 million square feet. The majority of the acquired buildings are located on or near hospital sites throughout 15 states.

"Our board of directors conducted a robust and thorough review of strategic alternatives and determined that this transaction is advisable to and in the best interests of our shareholders," Cogdell CEO Raymond Braun said in a statement.

Separately, Charlotte, N.C.-based Cogdell agreed to sell its Erdman design-build and development business to private equity firm Lubar & Co.

Lubar and Cogdell will each put in about $12 million in equity, which will go toward capitalizing Erdman, which has about $11 million in net working capital. The deal agreement gives Cogdell a 45-day go-shop period that is scheduled to be completed before Cogdell is sold to Ventas.

Ventas expects the Cogdell acquisition to add up to 5 cents per share on a full-year basis, excluding integration costs. Cogdell shareholders must still approve the deal and the transaction is also pending the successful completion of the Erdman sale.

In February, Ventas became the largest healthcare real estate investment trust in the U.S. when it acquired Nationwide Health Properties Inc. for $7.4 billion in stock and debt.

Shares of Ventas were trading 30 cents higher on Tuesday, at $55.24, with its market capitalization near $16 billion. Cogdell's stock was up more than 9%, at $4.28, bringing its market cap close to $219 million.

Centerview Partners LLC and Morgan Stanley advised Ventas. Willkie Farr & Gallagher LLP provided the buyer with legal counsel.

Cogdell received financial advice from Citigroup Inc. and legal representation from Alston & Bird LLP.