By now you have seen numerous generic chemical structures in which a single structure is drawn such that several possible alternatives are provided at different parts of the molecule being described. Each group of possible alternatives is commonly referred to as a Markush group and is best recognized by the format: “X is selected from the group consisting of A, B,and C” or “X is A, B, or C.”23 Some representative Markush groups are illustrated in Figure above. When a Markush group is used for claiming a chemical invention, the members of the group either need to belong to a common or recognized class or share at least one.


FIGURE :Markush chemical structure claim.

common function. A way to think of the Markush group is that the patent applicant believes that each member of the set can interchangeably serve the function of that position though some may still be preferable to others. The applicant should not include a member in the group unless they believe that group member would provide an operable embodiment of the invention.The power of Markush claiming is most evident when combinations of Markush groups are all used within the same claim. The number of possible embodiments of the invention multiply in a combinatorial fashion not practically reproduced by drawing all of the embodiments separately. The illustration of a compound claim containing multiple Markush groups is shown in Figure above. Each of the variable descriptors describes a separate and independent set of possibilities, even when the yare being chosen from the same group, in this case made evident by the fact that each variable descriptor has a separate designation (Ra, Rb, etc.). To make sure that each variable group cannot be construed as being dependent in any way one from another group, it is common practice to separately state that each variable is independently selected from the list of possibilities.

Markush groups will frequently contain possibilities that may not be precisely defined. For example, the set of atoms defined by “halogen” in Figure 5.7 is clearly understood. But note that within the Markush group describing the alternative possibilities for Rc and Rd in Figure 5.9, the group “C1-3 alkyl” was included. This definition actually allows for a range of possibilities at the position since it also covers a C1, C2, or C3 alkyl. A C1 alkyl is a methyl group (-CH3), a C2 alkyl is an ethyl group (-CH2CH3), and a C3 alkyl is a propyl group (-CH2CH2CH3). Sincea propyl alkyl group can exist as two isomers, it might also include (-CH(CH3)2),

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