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Patent landscape, scope, and claims: |
Patent 7,301,023: Scope and Claims Analysis for US Method Resolving Enantiomers of a Substituted Chiral Compound
US Patent 7,301,023 is a method claim estate focused on resolving enantiomers of a racemic drug-like compound defined by a highly substituted core scaffold (variables y, R4, R5, R6-R12 and additional substituent groups X/Y/Z). The claim scope is broad in chemical structure coverage because R groups include wide classes of substituents (including deuterated variants). The functional scope is also broad because the resolving step is written at the level of “a resolving compound having defined stereospecificity” that binds “at least one but not all” enantiomers to form a precipitate, followed by stand time and collection/recrystallization.
However, enforceability risk concentrates on (i) whether accused products/processes can be mapped onto the specific structural formula language and (ii) whether the “resolving compound” is used in a way that generates a stereospecific precipitate and permits collection of either precipitate or supernatant as recited.
What does US Patent 7,301,023 claim: method for resolving enantiomers of a defined substituted compound? (Claim scope overview)
Core claim type: single independent method claim (Claim 1) for enantiomer resolution of a racemate.
Claim 1 structure summary (functional skeleton):
- Mixing step (racemate + resolving agent):
- Mix a racemic mixture of enantiomers of a compound containing the claimed scaffold in a solvent with a resolving compound having defined stereospecificity.
- The resolving agent must bind at least one but not all enantiomers to form a precipitate that contains the bound enantiomer.
- Standing step (kinetics/time):
- Allow the mixture to stand for a time sufficient for substantial precipitation of the stereospecific enantiomer; the other enantiomer remains in solution.
- Separation step (either precipitate or solution):
- Depending on which enantiomer is desired, collect and purify precipitate or collect solution and recrystallize the enantiomer from that solution.
Immediate implication: the claim reads on standard resolution-by-diastereomeric salt/crystal formation workflows, but only if the specific scaffold definition is satisfied and the precipitate/supernatant handling matches the recited logic.
How broad is the chemical structure coverage in US 7,301,023 (variables y, R4, R5, R6–R12, X/Y/Z)?
The scaffold definition is the key gate. Claim coverage expands and contracts based on whether an accused compound fits within the permitted substitution space.
1) Variable y
- y = 0, 1 or 2
This provides discrete degrees of substitution/positioning freedom without fully open-ended structural divergence.
2) R4 substituent breadth
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R4 includes:
- H
- (C1–C6)alkyl and (C1–C6)alkylsulfonyl
- (C2–C6)alkenyl
- (C2–C6)alkynyl
- Optional substitutions include deuterium, hydroxy, amino, CF3, alkoxy, acyloxy, alkylamino, dialkylamino, cyano, nitro, acylamino, etc.
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Alternative R4 category:
- (C3–C10)cycloalkyl, optionally substituted by a similar menu including deuterium, hydroxy, amino, CF3, acyloxy, acylamino, aminoalkyl, cyano and nitro (including nitro(C1–C6)alkyl).
Practical reading: R4 allows medicinal-chemistry typical substituent patterns and tolerates deuteration. That increases the chance that close analogs still fall within scope if they share the same core.
3) R5 heterocycloalkyl coverage
- R5 is (C1–C9)heterocycloalkyl with extensive substitution lists (carboxy, cyano, amino, deuterium, hydroxy, alkyl/alkoxy/halo, acyl groups, sulfonamide-like motifs via R15R16N—CO—O— and related patterns, and sulfoxide/sulfone-type patterns via S(O)m).
- The claim also includes an explicit alternative “group of the formula” defined by parameters:
- a = 0–4
- b, c, e, f, g = 0 or 1
- d = 0–3
- X = S(O)n with n = 0–2
- Y = S(O)n with n = 0–2 or carbonyl
- Z = carbonyl, C(O)O—, C(O)NR— or S(O)n with n = 0–2
Practical reading: R5 is the largest “structure surface area.” It is written to catch heterocycle substituent variants and heteroatom oxidation-state changes (S(O)n, sulfoxide/sulfone-like).
4) R6–R11 and R12 substituent breadth
- R6–R11: H or (C1–C6)alkyl optionally substituted (deuterium/hydroxy/amino/CF3/acyloxy/acylamino/alkylamino/dialkylamino/cyano/nitro/acylamino).
- R12: broad functional set, including carboxy/cyano/amino/oxo and the same wide halo/alkyl/alkoxy/acyl/alkylamino/dialkylamino and sulfone/sulfoxide motifs via R15R16N—CO—O—, R15R16NS(O)m, R15S(O)mR16N, etc.
Enforcement impact: substituent latitude is high. For patent scope, the strongest limitation is not substituent selection but the underlying scaffold connectivity implied by “compound containing the structure of the formula” (not reproduced here) and the specific mapping of each substituent to the correct positions.
What does “resolving compound capable of binding at least one but not all enantiomers” mean for infringement design?
The method claim is not limited to a named resolving agent. Instead it requires three elements:
- Defined stereospecificity: the resolving compound must have predictable preference for one enantiomer over the other.
- Binding at least one but not all enantiomers: it must bind one enantiomer and exclude the other (or bind it much less so it does not substantially precipitate).
- Precipitate formation: precipitation must occur, and the precipitate must contain the bound stereospecific enantiomer.
Process mapping risk for defendants: if an accused process uses a resolving agent that forms a precipitate primarily containing one enantiomer, and the other remains in solution, it matches claim language even if the resolving agent is chemically distinct from those used in the patent examples (because the claim does not require a specific resolving compound identity).
Does US 7,301,023 cover salt formation, chiral acids, or chiral bases? How are pharmaceutically acceptable salts handled in the claim?
The claim references:
- “a compound containing the structure of the formula”
- “pharmaceutically acceptable acid addition salts thereof”
- “pharmaceutically acceptable base addition salts thereof”
- “free base thereof”
This means the racemate being resolved can be present as free base or as a pharmaceutically acceptable salt form consistent with the scaffold.
Key point for scope: the claim is anchored to resolution of the enantiomeric mixture of the scaffold compound, not to a specific salt identity. It therefore can cover operational workflows where the racemate is converted to a salt or where salts are already present.
When does enantiomer resolution using this method stop being covered: exclusivity timelines and patent expiration for US 7,301,023?
No dates, maintenance status, or terminal disclaimer terms are provided in the prompt. Without the filing date, priority data, and whether it is subject to PTA/terminal disclaimer, an accurate expiration calculation cannot be produced.
Result: timeline precision is not supportable from the provided information.
What other patents likely cover similar enantiomer-resolution methods: how many patents cover enantiomer resolution for the same scaffold?
No patent family list, assignee, priority, CPC/IPC results, or related documents are provided. The prompt includes only the single claim text.
Result: a quantitative landscape cannot be produced without bibliographic and family data tied to US 7,301,023.
How strong is US 7,301,023’s patent estate for generic or competitor entry: enforceability of a broad “resolution method”?
Strengths (claim language advantages)
- No specific resolving agent identity needed: the claim uses functional characteristics (stereospecific binding, precipitate formation).
- Standard resolution workflow is captured: mixing, standing for precipitation, then collection/recrystallization.
- Broad substituent scope: variables allow wide analog coverage, increasing the likelihood that close structural variants still satisfy the formula language.
Weaknesses (typical attack points for this kind of claim)
- Structural tethering risk: infringement depends on whether the accused racemate fits “a compound containing the structure of the formula” with the correct substituent variables. If a competitor uses a different scaffold outside those bounds, the claim may not apply.
- Process similarity is not enough if the structure is different: method claims often face “structure mapping” defenses.
- Potential obviousness vulnerabilities (functional broadness): enantiomer resolution by precipitating diastereomeric salts is a mature technique. If the patent’s novelty relies only on applying it to a broad set of scaffolds, validity challenges may focus on whether prior art already disclosed resolving similar compounds using stereospecific precipitating resolving agents.
(These are legal inferences from claim drafting style; the prompt provides no cited prior art or examiner history.)
What patent litigation affects US 7,301,023: Paragraph IV, Hatch-Waxman, or biosimilar relevance?
No litigation docket, Orange Book linkage, or FDA product association is provided in the prompt.
- Paragraph IV: Only relevant if the scaffold compound is an FDA-listed drug with a listed reference product.
- Biosimilar litigation: Only relevant if the compound is biologic or relies on biosimilar regulatory pathways.
Result: litigation impact cannot be accurately characterized from the provided information.
What is the Orange Book status of US 7,301,023 and the associated drug product?
No NDA/ANDA/RLD name, listed patents, or Orange Book identifiers are provided.
Result: Orange Book status and listed-patent scope cannot be determined from the prompt alone.
Which formulations are protected by US 7,301,023: does it claim dosage forms or only resolution processing?
Claim 1 is a method for resolving enantiomers, not a dosage-form claim.
- It covers the resolution process for a racemic mixture of a specific scaffold (including salts/free base).
- It does not specify tablets, capsules, injectables, or particular excipient compositions.
- It does specify a solvent conceptually and a precipitate/supernatant handling flow.
Practical takeaway: the strongest protection is against manufacturing or development processes that resolve the enantiomer using the claimed scaffold and the claimed precipitate-based resolution scheme.
How does US 7,301,023 compare with typical enantiomer-resolution patent claims (what is distinctive in this claim)?
Compared with “narrow resolving agent” patents, US 7,301,023 is distinctive for:
- Functional breadth on resolving agent identity (stereospecific binding and precipitate creation).
- Very broad substituent language for the scaffold, expanding the set of compounds that the method can resolve.
Compared with “only salt forms” methods, it is distinctive because it explicitly includes:
- free base and pharmaceutically acceptable acid/base addition salts of the scaffold compound.
Key features of Claim 1 you should map for infringement analysis (checklist format)
- Is the starting material a racemic mixture of the enantiomers of a compound that fits the scaffold formula with y = 0–2 and R4/R5/R6–R12 within the enumerated classes?
- Is a resolving compound used that has defined stereospecificity?
- Does the resolving compound bind at least one but not all enantiomers to form a precipitate containing the bound enantiomer?
- Is the mixture allowed to stand to achieve substantial precipitation of the stereospecific enantiomer while the other remains in solution?
- Is the desired enantiomer obtained by either:
- collecting and purifying the precipitate, or
- collecting the solution and recrystallizing the enantiomer from it?
Key Takeaways
- US 7,301,023 is a method-of-resolution claim centered on racemate enantiomer separation via a stereospecific resolving agent that produces a precipitate enriched in one enantiomer.
- The chemical scope is broad due to extensive permitted substituent ranges for R4, R5, R6–R11, and R12, including deuteration and sulfur oxidation-state variants (S(O)n).
- The claim’s enforceability hinges on (i) structural mapping to the formula scaffold and (ii) whether the process produces stereospecific precipitation with the claimed collect/recrystallize logic, not on any specific named resolving agent.
- The provided prompt does not include bibliographic or Orange Book data, so expiration, litigation, and product linkage cannot be stated from the given text.
FAQs
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Can US 7,301,023 be infringed if a different resolving agent is used than the one in the examples?
The claim does not require a named agent; it requires functional stereospecific binding and precipitate formation.
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Does the claim cover resolution of free base as well as acid/base salts?
Yes. Claim 1 includes pharmaceutically acceptable acid addition salts, base addition salts, and free base of the scaffold compound.
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If a process yields both enantiomers in precipitate, does it still meet “at least one but not all”?
The claim requires binding of at least one enantiomer and not all, so mixed precipitation that binds both enantiomers as to “all” would be a mismatch.
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Is this patent about producing a dosage form (tablet/capsule) or about manufacturing steps?
Claim 1 is about a manufacturing/resolution method, not a finished dosage form.
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Does the claim cover deuterated analogs of the substituents?
Yes. Multiple substituent definitions expressly permit optional deuterium substitution.
References
- US Patent 7,301,023, Claim 1 text (provided in prompt).
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