Icahn sued Occidental in Delaware Court of Chancery last May seeking financial records and details of its negotiations with Anadarko. He has since committed to a proxy fight to appoint new management and accelerate asset sales to repay debt taken on with the $38 billion deal.

In a sharply worded decision, Vice Chancellor Joseph Slights wrote Icahn's complaints of Occidental mismanagement "appear to be nothing more than disagreements" with the company's directors and his lawsuit failed to show how the documents would advance his proxy contest.

"We intend to appeal his decision because we believe understanding what happened in the Oxy boardroom is very important to our proxy fight and for all stockholders," said Andrew Langham, general counsel for Icahn Enterprises.

Occidental did not respond to requests for comment.

Icahn last week disclosed the sale of 10 million shares of the oil and gas producer, reducing his Occidental holdings by nearly a third, according to a letter to shareholders. His stake, valued at about $1.6 billion last May, was worth about $900 million after the sale, he wrote.

Replacing the company's leadership would cause its value to "meaningfully increase," he said in an interview last week. Icahn then declined to say how much he lost on the sale of the 10 million Occidental shares.

Occidental traded at $37.76 on Thursday, down from $65.33 on April 12 when the company's interest in Anadarko was first disclosed.

(Reporting by Jennifer Hiller; writing by Gary McWilliams; Editing by Sandra Maler and Tom Brown)