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Stereochemistry

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Title: Stereochemistry


1
Stereochemistry
  • and

BEYOND
Christopher Low christopher.low_at_uspto.gov 571-272-
0951
2
Example 1
  • Application claims A compound of Formula X with
    melting point y.

3
Prior art disclosure
  • A compound of Formula X.
  • (no melting point given)

4
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.

5
Example 2
  • Application claims A stereomer of Formula X.

6
Prior art discloses a biologically active
racemic mixture
7
Do we reject?
  • Yes.
  • Rejection is appropriate whether the stereomer is
    isolated or not.
  • Subject to secondary considerations.

8
Example 3
  • Application claims A stereomer of Formula X.

9
Prior art discloses a racemic mixturethere is
no motivation for resolution of the isomers
10
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.

11
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

12
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)

13
Enantiomeric Excess (ee)
  • Means one enantiomer is present in a certain
    amount over the other enantiomer
  • Results in optical activity of the composition

14
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.

15
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

16
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

17
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.

18
Polymorphism
  • The existence of a substance in two or more
    crystalline forms which are significantly
    different in physical or chemical properties.

19
  • 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.

20
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.

21
Thank you
  • Christopher Low
  • Supervisor, Art Unit 1614
  • 571-272-0951
  • Christopher.low_at_uspto.gov
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