Morgan Stanley, continuing its aggressive move into real-estate investments, has purchased 49% of Crescent Resources, Duke Energy Corp.’s commercial and residential real-estate development subsidiary.

Duke Energy, which formed Crescent more than 40 years ago to develop country club communities, apartments and other some commercial developments in nine Southeastern and Southwestern states, said the deal values Crescent at $2.1 billion. The utility is keeping a 49% stake in what it calls a joint venture with Morgan Stanley. Arthur Fields, Crescent’s chief executive, owns 2% of the company.

Crescent, which has about 400 employees and will retain its name, is expected to produce earnings before interest and tax expenses of $250 million in 2006, Duke Energy said earlier this year.The figure includes continued and discontinued operations, said Elizabeth Bennett, a Duke spokeswoman.

Duke Energy loaned Crescent about $1.2 billion to complete the leveraged recapitalization, almost all of which will be paid back to the utility, Ms. Bennett said. The debt will be classified off of Duke Energy’s balance sheet.

Duke Energy has been reversing an earlier strategy of diversifying beyond its core electricity businesses. Earlier this year it said it would spin off its gas businesses by year-end.

“The new structure is consistent with our plan to focus primarily on the power business by reducing our investment and risk profile associated with non-core businesses,” the president and chief executive officer of Duke Energy, James E. Rogers, said in a prepared statement.

Morgan Stanley’s real estate group, a part of its investment banking operations, is buying Crescent through Morgan Stanley Real Estate Fund V US, which is still raising money from investors. Duke and Crescent are longtime investment banking clients of Morgan Stanley, Ms. Bennett said.

Banc of America Securities LLC, a Bank of America Corp. (BAC) unit, advised Duke Energy on the Crescent Resources transaction. Morgan Stanley represented itself.

Morgan Stanley, which has bought $87.7 billion of real estate worldwide since 1991, currently manages eight funds that invest in overseas and domestic real estate. At the end of August, the so-called MSREF V fund said it will buy Glenborough Realty Trust (GLB), a real-estate investment trust, for about $1.9 billion.

Earlier this year, the fund and two outside partners paid $1.5 billion to buy and take private the Town and Country Trust, a multifamily real estate investment trust. Last week the fund and Gale International said it will buy and develop 23 acres in South Boston owned by News Corp., and earlier this year it signed a $150 million agreement with a Washington, D.C., economic development corporation to invest in poor neighborhoods.