Stereochemistry

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Stereochemistry

• and

BEYOND
Christopher Low christopher.low_at_uspto.gov 571-272-
0951
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Example 1

• Application claims A compound of Formula X with
  melting point y.

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Prior art disclosure

• A compound of Formula X.
• (no melting point given)

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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.

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Example 2

• Application claims A stereomer of Formula X.

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Prior art discloses a biologically active
racemic mixture
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Do we reject?

• Yes.
• Rejection is appropriate whether the stereomer is
  isolated or not.
• Subject to secondary considerations.

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Example 3

• Application claims A stereomer of Formula X.

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Prior art discloses a racemic mixturethere is
no motivation for resolution of the isomers
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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.

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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 applicants
  claim makes the claim different from the racemate
  in the art.
• though it may not be patentably distinct

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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)

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Enantiomeric Excess (ee)

• Means one enantiomer is present in a certain
  amount over the other enantiomer
• Results in optical activity of the composition

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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 86ee.

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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

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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

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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.

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Polymorphism

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

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• 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.

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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.

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Thank you

• Christopher Low
• Supervisor, Art Unit 1614
• 571-272-0951
• Christopher.low_at_uspto.gov