The Royal Society of Chemistry's Merck Index is a source of information on chemicals, drugs and biologicals. The advanced search offers a number of ways to discover chemicals using both text and properties. Researchers may also search by structure and named reactions.
In 1925 after Eugene Markush's appeal was upheld, the USPTO officially began allowing instance where a ‘virtual set’ of compounds is considered with R-groups at specified positions selected from a group consisting of a closed listing of potential radical substituents. These structures became know as Markush Claims and allow inventors to patent members of a class of compounds that have a similar function.
Generic type of description of chemicals used to summarize a potentially large set of closely related chemicals in a single condensed representation
Core chemical structure and a list of possible substituents (R-Groups)
Four types of R-groups
Substituent variation: allows different substituents at a position
Position variation: allows different attachment points for a substituent
Frequency variation: allowing substituents to occur multiple times
Homology variation: using generic expressions covering many specific substituents
Markush Structure Search Tutorials
Tutorial | Understand the Value of a Markush Structure Search
Tutorial | Understand the Types of Markush Searches