US Patent 4,024,175 Scope and Claims: What the Claims Cover and How Broad the Patent Estate Is
US 4,024,175 is a small-molecule compound patent that claims a genus defined by a general structural formula with two tunable parameters: (i) a substituent R1 that is hydrogen or a “lower alkyl” group, and (ii) a ring-size parameter n that is 4, 5, or 6 (as written in the provided claim set). The independent claim 1 is a structural Markush-style genus claim, and claims 2 to 11 carve out specific exemplified embodiments including amino-methyl cycloalkyl acetic acids and esters (cyclopentane, cyclohexane, cycloheptane), plus specific salt forms (notably toluene sulfonate and benzene sulfonate).
This claim architecture typically yields a strong core for infringement by “identity and equivalents” within the claimed scaffold, while leaving surrounding patent risk to continuation/divisional families, related salt/form-specific patents, and potential method-of-use or process patents not contained in this single compound patent.
What does claim 1 cover in US 4,024,175: general formula, R1 “lower alkyl,” and n = 4 to 6?
Claim 1 is the scope driver. It defines:
- A compound “of the general formula” (structure shown as ##STR6## in the prompt).
- R1 is either:
- hydrogen, or
- a “lower alkyl radical.”
- n is 4, 5 or 6.
- Pharmacologically compatible salts are expressly included.
How to read the genus (practical scope consequences)
- Ring-size parameter (n): Setting n to 4, 5, or 6 limits the scaffold to a defined series of cyclic ring members corresponding to those n values in the disclosed formula. If n maps to cycloalkyl ring size in the scaffold (as the dependent claims suggest), the genus likely covers cyclopentane/cyclohexane/cycloheptane analogs (with one of those ring sizes potentially not aligned with n values as written in the prompt, discussed below).
- R1 = H or lower alkyl: This gives latitude for substituting a single lower-alkyl group at the R1 position while keeping the rest of the scaffold constant. From a freedom-to-operate lens, a competitor changing only that position within “lower alkyl” typically remains within literal scope, depending on how “lower alkyl” is defined in the specification and prosecution history.
- Salts are within claim 1: Even if an accused product uses a specific salt form, the claim is written so that the salt is itself covered, provided it is “pharmacologically compatible.” That term is usually litigated based on examples, definitions, and general salt selection practice in the art.
Potential internal inconsistency to flag (only based on your provided claim listing)
Dependent claims list cycloheptane embodiments explicitly (claims 4 and 8), while claim 1 states n is 4, 5 or 6. If the general formula uses n to map directly to the ring size, the presence of cycloheptane-specific dependent claims suggests one of the following is true:
- n in claim 1 does map to cycloheptane through the formula’s indexing scheme (so “n=6” could correspond to a cycloheptane ring in that indexing), or
- the “n=4,5,6” in your extracted text may be a transcription artifact.
Either way, the dependent claims strongly indicate cycloheptane-containing compounds are intended to fall within the overall patent coverage.
Which specific compounds are enumerated in dependent claims 2 to 11?
Claims 2 to 11 narrow the genus by naming specific structures and, in two instances, specifying salts.
Dependent claim coverage table (from your claim set)
| Claim |
Limitation type |
Specific compound named in the claim |
| 2 |
Example compound |
1-Aminomethyl-1-cyclohexane-acetic acid |
| 3 |
Example compound |
Ethyl 1-aminomethyl-1-cyclohexane-acetate |
| 4 |
Example compound |
1-Aminomethyl-1-cycloheptane-acetic acid |
| 5 |
Example compound |
1-Aminomethyl-1-cyclopentane-acetic acid |
| 6 |
Example compound |
Methyl 1-aminomethyl-1-cyclohexane-acetate |
| 7 |
Example compound |
n-Butyl 1-aminomethyl-1-cyclohexane-acetate |
| 8 |
Example compound |
Methyl 1-aminomethyl-1-cycloheptane-acetate |
| 9 |
Example compound + salt |
n-Butyl 1-aminomethyl-1-cyclopentane-acetate toluene sulfonate |
| 10 |
Example compound + salt |
1-Aminomethyl-1-cyclopentane-acetate benzene sulfonate |
| 11 |
Example compound |
n-Butyl 1-aminomethyl-1-cyclopentane-acetate |
What this enumeration does legally
- It anchors claim scope: Even though claim 1 is broad, the enumerated claims provide concrete embodiments that can guide claim construction (including for terms like “lower alkyl” and “pharmacologically compatible salts,” if disputes arise).
- It covers both acids and esters: The dependent claims span carboxylic acids and ester derivatives, meaning competitors cannot rely on “we changed the acid to an ester” to escape coverage if the ester falls within the genus (and/or is one of the expressly named embodiments).
- It shows salt acceptance for at least two sulfonates: Toluene sulfonate and benzene sulfonate are explicitly included. That supports a position that other therapeutically acceptable salts of the same active base may also be encompassed under claim 1’s “pharmacologically compatible salts” language.
How broad is “lower alkyl” and where are typical boundary lines for infringement risk?
Claim 1 includes “R1 is hydrogen or a lower alkyl radical.” That phrase is usually construed by:
- the patent specification’s definition or examples,
- how “lower alkyl” is used in the chemical arts,
- prosecution statements (if any) and dictionary-style meaning.
Practical impact on design-around
- If an attempted design-around changes R1 from a lower-alkyl to a higher-alkyl, it may exit literal scope but can create:
- doctrine-of-equivalents risk, and
- validity risk if the claim is construed narrowly.
- If a competitor keeps R1 within lower alkyl and changes elsewhere, they remain within the structural genus unless they move outside the n ring-size limitations or alter the core scaffold in a way that breaks the general formula match.
What likely matters most for literal coverage
- Whether the competitor’s compound matches the Markush structure at every atom position required by ##STR6##.
- Whether the competitor uses a salt form that qualifies as “pharmacologically compatible.” For sulfonate salts, the patent’s own dependent claims suggest broad acceptance.
What patent landscape typically surrounds a US compound genus like 4,024,175?
A single compound patent like US 4,024,175 often sits inside a larger family cluster, with related patents on:
- specific substitutions not captured fully by the broad genus,
- specific salts (separate from the base compound genus),
- formulation patents (tablets/capsules, sustained release, salts for stability),
- method-of-use patents (pharmacological indications),
- and manufacturing/process patents.
How to assess the broader estate (without relying on unstated family data)
Based on the claim content you provided, the “hard” scope inside 4,024,175 itself is for:
- the general formula scaffold with n = 4 to 6,
- R1 = H or lower alkyl,
- and pharmacologically compatible salts.
That means the largest infringement exposure from this specific patent typically comes from:
- any active ingredient matching the scaffold (acids or ester derivatives),
- any active ingredient delivered as a pharmaceutically acceptable salt (including sulfonates),
- and variants that remain within the allowed R1 and ring-size limits.
If the company is evaluating infringement or licensing value, the next-stage landscape step is usually to check for:
- continuation patents from the same application family that add new dependent embodiments,
- separate patents claiming salts of the same compounds (often filed to strengthen commercial coverage),
- and any method-of-use patents that might create separate enforcement hooks even if a generic chooses a non-covered salt form.
(No additional specific patents, assignees, or family members are listed in your prompt. Without that, this analysis can’t enumerate other US patent numbers or jurisdictions.)
What formulations are protected by US 4,024,175?
None are claimed in the provided claims. The claims you provided are directed to compounds and salts (chemical structure claims). That typically means:
- the patent protects the active ingredient and its qualifying salts,
- but does not, on its face, protect a particular dosage form (tablet, capsule), manufacturing method, or release profile.
Commercial formulation IP would likely be covered by separate patents if they exist (outside the claim set you supplied).
What generic entry risks exist for compounds matching the disclosed scaffold?
If a proposed generic product’s API falls within claim 1’s genus (or within claims 2 to 11’s enumerated embodiments), the generic faces:
- literal infringement risk for the API as sold,
- infringement risk via salt form if the generic uses a “pharmacologically compatible” salt.
Risk-reduction paths (within the constraints of this patent’s claim language)
- Move outside the general formula (core scaffold mismatch).
- Move outside the n constraint.
- Use an R1 substitution not considered “lower alkyl.”
- Use a salt that is argued not to be “pharmacologically compatible.” This is harder when the dependent claims show sulfonate salts are included and the claim 1 already expands to “pharmacologically compatible salts.”
Because claim 1 is a genus claim and dependent claims explicitly list acids and esters, design-around generally requires a structural change rather than a simple salt switch.
How strong is the patent estate for this scaffold: what the claim structure implies
Strength indicators from the claim set
- Genus claim with defined substitutions: Claim 1 provides broad coverage across a series (n = 4 to 6; R1 = H or lower alkyl).
- Salts included: Claim 1 explicitly covers salts, which reduces “salt-only” design-around.
- Multiple exemplified acids and esters: Dependent claims reinforce that both esterified and acid forms are intended subject matter.
Litigation posture likely to be favorable to the patentee (based on claim mechanics)
- If infringement turns on structure matching, a Markush genus claim often supports straightforward chemical comparison.
- Enumerated dependent claims provide reference points for construction and can help limit interpretive disputes about which embodiments are within intended coverage.
Key takeaways
- US 4,024,175 claim 1 is a broad structural genus covering compounds defined by a general formula with R1 = hydrogen or lower alkyl and n = 4, 5, or 6, plus pharmacologically compatible salts.
- Dependent claims 2 to 11 enumerate specific embodiments including aminomethyl cycloalkyl acetic acids and their ester derivatives, spanning cyclopentane, cyclohexane, and cycloheptane ring systems.
- The patent expressly includes at least two sulfonate salts in dependent claims: toluene sulfonate and benzene sulfonate, while claim 1 also covers “pharmacologically compatible salts” more generally.
- For generic design-around, escaping this patent typically requires moving outside the claimed structural scaffold, not merely changing salt or switching between acid/ester within the enumerated pattern.
FAQs
1) Does US 4,024,175 protect both free base and salt forms?
Yes. Claim 1 includes “pharmacologically compatible salts,” and dependent claims specify sulfonate salts.
2) If a product uses a different ester group (vs methyl/ethyl/butyl) does it fall outside the patent?
Not automatically. Claim 1’s general formula likely covers the ester derivatives within its structural definition; dependent claims list specific ester examples but do not limit the genus to only those.
3) Are cyclopentane and cyclohexane analogs covered even if they are not explicitly listed?
Yes in principle, if they fit the claim 1 general formula with the allowed n values and allowed R1 group definition.
4) Can a generic avoid infringement by changing only the salt to a non-sulfonate salt?
Only if the new salt is argued not to be “pharmacologically compatible” and not covered by claim 1’s salts language. Sulfonate salts are expressly included, which makes simple salt substitution a weaker exit strategy.
5) Does this patent cover a tablet, capsule, or sustained-release formulation?
Not based on the provided claim set. The claims you provided target compounds and salts, not dosage-form or formulation methods.
References
- United States Patent No. 4,024,175. (Claims text provided in the prompt).
