A Markush structure, Markush group, or a Markush claim is a representation of alternatively useable members. Markush structures are frequently used with chemical structures to indicate a group of related chemical compounds. They are commonly used in chemistry texts and in patent claims. Markush structures are depicted with multiple independently variable groups, such as R groups in which a side chain can have varying structure.^[1] This more general depiction of the molecule, versus detailing every atom in the molecule, is used to protect intellectual property. The company which applies for a patent makes a general claim for the usage of the molecule without revealing to their competitors the exact molecule for which they are declaring a useful application.^{[citation needed]}

Markush structures are named after Eugene A. Markush, founder of the Pharma Chemical Corporation in New Jersey. He was involved in a legal case that set a precedent for generic chemical structure patent filing, Ex parte Markush, 1925 Dec. Comm'r Pat. 126, 127 (1924).^{[1] [2]} The patent filing was US Application 611,637, filed January 9, 1923. Markush was awarded a patent from the US Patent Office for “Pyrazolone Dye and Process of Making the Same” on August 26, 1924.^[3]

The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject. You may improve this section, discuss the issue on the talk page, or create a new section, as appropriate. (July 2018) (Learn how and when to remove this message)

In describing a chemical, a Markush structure allows the patent-holder to list several active/effective structural formulas.

In the United States, Markush structures are frequently used to claim alternative components. The correct format for a Markush structure is "closed."^[4] In other words, the claim language defined by the Markush structure requires selection from a closed group.^[5] One way of claiming a Markush structure follows the format: “a chemical selected from the group consisting of A, B, and C” where A, B, and C are alternative chemicals.^[6]

A claimed Markush structure may be improper if (1) the members of the Markush structure do not share a "single structural similarity," or (2) if the members of the Markush structure do not share a common use.^[7]

• Molecule editor
• Chemical file format
• List of patent claim types § Markush

• Media related to Markush structures at Wikimedia Commons