stereochemistry and christopher low [email protected] 571-272-0951
TRANSCRIPT
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?
Yes. 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?
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 mixturethere is no motivation for resolution of the isomers
Do we reject?
Yes. 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? In a racemic mixture, the optically active
compound is mixed with its optical opposite.
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?
Can require isolation from all other species 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)
Means one enantiomer is present in a certain amount over the other enantiomer
Results in optical activity of the composition
How %ee is calculated
%ee is the difference between the relative proportions of the two enantiomers.
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
Limiting the environment• essentially the “compound” claim is hybridized
to a “composition” claim• certain additional elements are excluded or
significantly reduced
When else is this technique useful?• Chemical Purity• Polymorphism
Chemical Purity
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 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
The existence of a substance in two or more crystalline forms which are significantly different in physical or chemical properties.
Racemate• Two stereoisomers
present in a single composition.
• Stereoisomers are not patentable over their racemate.
• Unless the environment of the compound is sufficiently limited.
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.
