Stereochemistry and Christopher Low

Example 1: Application claims: A compound of Formula X with melting point y.

Prior art disclosure: A compound of Formula X. (no melting point given)

Do we reject? w Yes. w Melting point is a physical property and inheres from the structure of the compound. Note: other physical properties (e.g., optical properties) are also inherent in the compound itself.

Example 2: Application claims A stereomer of Formula X.

Prior art discloses a biologically active racemic mixture

Do we reject? w Yes. Rejection is appropriate whether the stereomer is isolated or not. Subject to secondary considerations.

Example 3: Application claims A stereomer of Formula X.

Prior art discloses a racemic mixture there is no motivation for resolution of the isomers

Do we reject? w Yes. w However, rejection may be overcome by limiting the environment of the optically active compound Rejection may not be overcome if limiting the environment is taught in the prior art.

What is the environment of the compound? w In a racemic mixture, the optically active compound is mixed with its optical opposite. w Excluding the opposite isomer in applicant’s claim makes the claim different from the racemate in the art. though it may not be patentably distinct

How can optical opposite be excluded? w Can require isolation from all other species w If they are enantiomers Can exclude the undesired enantiomer by requiring some degree of optical purity by reciting that the desired enantiomer is in x% enantiomeric excess (if supported by spec)

Enantiomeric Excess (%ee) w Means one enantiomer is present in a certain amount over the other enantiomer w Results in optical activity of the composition

How %ee is calculated w %ee is the difference between the relative proportions of the two enantiomers. w A reaction or separation producing 93% of one enantiomer and 7% of the other is said to produce the desired enantiomer in 86%ee.

Beyond Stereochemistry w Limiting the environment essentially the “compound” claim is hybridized to a “composition” claim certain additional elements are excluded or significantly reduced w When else is this technique useful? Chemical Purity Polymorphism

Chemical Purity w Claims can be limited by a purity clause e.g., 99 and 44/100 percent pure exclusion of a specie or a genus e.g., free of alcohol function or property effective to eliminate a specie or genus

Just like our stereochemistry example w If a purity technique is used, then prior art will be avoided if there is no motivation to have excluded or reduced the identified element.

Polymorphism w The existence of a substance in two or more crystalline forms which are significantly different in physical or chemical properties.

w Racemate Two stereoisomers present in a single composition. Stereoisomers are not patentable over their racemate. Unless the environment of the compound is sufficiently limited. w Polymorph Two (or more) crystals present in a single composition. Single crystals are not patentable over their polymorph. Unless the environment of the compound is sufficiently limited.

When the art discloses a compound in a composition and you want the compound alone... you can claim the compound as being free of the other elements in the composition provided the art is deplete of motivation to have separated them.

Thank you Christopher Low Supervisor, Art Unit