Peapack, N.J.’s Pharmacia & Upjohn Inc. hired New York’s Davis Polk & Wardwell and St. Louis-based Monsanto Co. turned to New York’s Wachtell, Lipton, Rosen & Katz to handle their $23.3 billion merger. The stock-for-stock transaction is considered a merger of equals, but the combined company will be headquartered in New Jersey.

The Davis Polk attorneys representing Pharmacia are partners Peter R. Douglas, Lydia E. Kess, Mario J. Verdolini, Gail A. Flesher, Patrick A. Bradford and Joel M. Cohen; and associates John H. Butler, Lisa G. Baltazar, Michael Davis, Hao Liu, Michelle K. Lynd, Angelica Kwan, Marina Martino Casani, Jean M. McLoughlin, Shelly White, Dana L. Willis and Manisha M. Sheth. Pharmacia’s in-house crew was led by Richard T. Collier, senior vice president and general counsel, and Don W. Schmitz, vice president, associate general counsel and corporate secretary.