United States Patent 3,821,228: Scope, Claim Breadth, and U.S. Landscape
What does US Drug Patent 3,821,228 claim, at the compound level?
US Patent 3,821,228 is directed to a family of substituted tetrahydroquinoline compounds and is limited to particular substitution patterns through a set of variable groups (R1, R2, R3, R5, R6, R8) and a specific compound set exemplified by claim 7.
From the provided claim text, the claim set you cited contains dependent claims that narrow a broader claim 1 by enforcing specific values for substituents:
-
Claim 2 fixes:
- R3 = hydrogen
- R5 = chloro
- R6 = hydrogen
- R8 = hydrogen
-
Claim 3 further fixes (on top of claim 2):
- R1 = isopropyl
- R2 = hydrogen
-
Claim 4 fixes (relative to claim 1):
- R3 = hydrogen
- R5 = nitro
- R6 = hydrogen
- R8 = hydrogen
-
Claim 5 further fixes (on top of claim 4):
- R1 = isopropyl
- R2 = hydrogen
-
Claim 6 further fixes (on top of claim 4):
-
Claim 7 is a specific named compound:
- 6-Hydroxymethyl-2-isopropylaminomethyl-7-nitro-1,2,3,4-tetrahydroquinoline
This structure implies the patent’s core inventive space is a tetrahydroquinoline scaffold with:
- a hydroxymethyl substituent at a fixed position (consistent with claim 7),
- a nitro (or chloro in the chloro branch),
- and a constrained aminomethyl substitution pattern controlled by R1 and R2 (isopropyl/hydrogen or ethyl/ethyl in the dependent claims you provided).
How broad is the scope based on the dependent-claim matrix you provided?
The breadth is best read as a substitution grid: claim 1 is the platform, and claims 2-6 lock down substituent identities. Under that construction:
Substitution constraints explicitly locked by the claims you provided
| Claim |
R3 |
R5 |
R6 |
R8 |
R1 |
R2 |
Resulting scope segment |
| 2 |
H |
chloro |
H |
H |
(not fixed) |
(not fixed) |
“chloro” branch with H at the other listed positions |
| 3 |
H |
chloro |
H |
H |
isopropyl |
H |
chloro branch + isopropylamino substituent variant |
| 4 |
H |
nitro |
H |
H |
(not fixed) |
(not fixed) |
“nitro” branch with H at the other listed positions |
| 5 |
H |
nitro |
H |
H |
isopropyl |
H |
nitro branch + isopropylamino substituent variant |
| 6 |
H |
nitro |
H |
H |
ethyl |
ethyl |
nitro branch + dialkylamino substituent variant |
| 7 |
(implied by numbering) |
nitro present |
(implied) |
(implied) |
isopropyl |
H |
specific final compound: 6-hydroxymethyl-2-isopropylaminomethyl-7-nitro-1,2,3,4-tetrahydroquinoline |
What is not fixed by these claims (in the text provided)
Because you provided only claims 2-7, the following aspects that often control actual infringement or design-around are not shown:
- The exact structure and definition in claim 1 that sets the base scaffold and which R positions correspond to which atoms/locations.
- Whether other R variables exist beyond the ones stated (you only provided R1, R2, R3, R5, R6, R8).
- Any stereochemistry, salt forms, tautomer limits, or process limitations.
Even with those omissions, the dependent claims clearly establish that the compound scope has at least two substituent series:
- chloro series (claim 2, claim 3), and
- nitro series (claim 4-7, with additional dialkyl variation in claim 6).
Where do the claims cluster around named chemical identity?
Claim 7 is a “closure point” because it ties the variable claim language to a single chemical name. It identifies:
6-Hydroxymethyl-2-isopropylaminomethyl-7-nitro-1,2,3,4-tetrahydroquinoline (claim 7).
This matters for landscape work because claim 7 typically anchors:
- the exact substitution pattern that later filings often map onto (or avoid),
- and the earliest “known exact” structure for the scaffold.
Given that claim 7 corresponds to the nitro branch and the isopropyl + hydrogen amino substitution pattern, it matches the dependent constraints of claim 5:
- R5 = nitro
- R1 = isopropyl
- R2 = hydrogen
and with R3/R6/R8 fixed to hydrogen in claim 4/5.
So claim 7 is effectively the literal species within the broader nitro/isopropylamino slice.
What is the likely patent-prosecution intent behind the dependent-claim pattern?
The dependent-claim structure does three things typical of compound patents:
-
Species capture with nested claims
- The “chloro” and “nitro” branches are separated early (claims 2 and 4).
- Each branch then captures the key amino substitutions (claims 3 and 5) and a more substituted amino variant (claim 6).
-
Variable group control
- R3/R6/R8 are fixed to hydrogen in both branches, narrowing the usable scaffold to a specific substitution pattern and reducing the likelihood that unrelated analogs read onto the claim 1 definition.
-
A named example for enforcement clarity
- Claim 7 forces an unambiguous target compound that can be used to interpret the meaning of the variable substitutions in the earlier claims.
What is the enforceable U.S. landscape based on this claim set?
A complete patent landscape (other assignees, priority chain, continuation status, term, and related family members) requires the full bibliographic record and the complete claims of US 3,821,228 plus file-history data and citation records. Those are not present in the input you provided.
Under the strict scope you gave (dependent claims 2-7 and one named species), the only defensible landscape statements are structural: the patent’s coverage is concentrated in tetrahydroquinoline derivatives with a fixed hydrogen pattern on R3/R6/R8, with chloro vs nitro at R5 and limited dialkyl variation at the amino substituent positions.
Practical landscape implication for R&D and design-around
Within the constraints visible in your claims:
- The patent is strongest against competitors whose candidates include:
- the nitro substitution at the R5 position,
- hydrogen at R3/R6/R8 positions,
- and the specified aminomethyl alkylation patterns (isopropyl/hydrogen or ethyl/ethyl), including the specifically named compound in claim 7.
- A plausible design-around direction, based only on the visible claim narrowing, would be to alter one of the locked variables:
- change R5 away from nitro (or chloro if targeting the chloro branch),
- or change one of the fixed hydrogen positions (R3/R6/R8),
- or change the aminomethyl substitution pattern away from isopropyl/hydrogen or ethyl/ethyl.
This is not a legal freedom-to-operate opinion; it is the direct consequence of the dependent-claim lattice you provided.
Key claim-by-claim scope read-through (infringement mapping logic)
Claim 2 (chloro branch)
Claim 2 covers any compound that satisfies claim 1 and additionally has:
- R3 = hydrogen
- R5 = chloro
- R6 = hydrogen
- R8 = hydrogen
So claim 2 is a subset of claim 1, isolating the chloro substitution at the R5 position while enforcing hydrogens on the other listed positions.
Claim 3 (chloro + isopropyl/hydrogen amino pattern)
Claim 3 is claim 2 plus:
- R1 = isopropyl
- R2 = hydrogen
So claim 3 captures a smaller species within the chloro subset.
Claim 4 (nitro branch)
Claim 4 is claim 1 plus:
- R3 = hydrogen
- R5 = nitro
- R6 = hydrogen
- R8 = hydrogen
This isolates the nitro substitution pattern as a second major subset.
Claim 5 (nitro + isopropyl/hydrogen)
Claim 5 is claim 4 plus:
- R1 = isopropyl
- R2 = hydrogen
So claim 5 captures a species in the nitro subset with isopropylamino/hydrogen.
Claim 6 (nitro + ethyl/ethyl amino)
Claim 6 is claim 4 plus:
So claim 6 captures a different nitro species with a more substituted amino pattern.
Claim 7 (named species)
Claim 7 is the explicit identity:
- 6-Hydroxymethyl-2-isopropylaminomethyl-7-nitro-1,2,3,4-tetrahydroquinoline
It operationalizes claim 5’s substitution pattern in a single unambiguous structure.
What does this mean for investors or licensing teams?
With the limited claim text, the defensible conclusion is:
- The patent’s compound enforcement envelope (at least as reflected by dependent claims 2-7) concentrates on a nitro series and a chloro series of tetrahydroquinoline analogs.
- The nitro series includes at least two aminomethyl substitution patterns:
- isopropyl/hydrogen (claim 5 and claim 7),
- ethyl/ethyl (claim 6).
- The fixed hydrogen positions (R3/R6/R8 all hydrogen in claims 2 and 4) reduce the number of potential analogs that could fall under these dependent claims.
Without claim 1 text, you cannot accurately map the full scope (including whether R1/R2 have wider options in claim 1 beyond what dependent claims narrow). But you can reliably state that these dependent claims create at least three enforceable “species or narrow groups” (chloro/isopropyl, nitro/isopropyl, nitro/ethyl-ethyl), with claim 7 being the clearest named target.
Key Takeaways
- US 3,821,228 claim coverage shown in your excerpt is dominated by tetrahydroquinoline compounds where R3, R6, and R8 are hydrogen and R5 is either chloro or nitro.
- The aminomethyl substitution at the R1/R2 positions is constrained in dependent claims to isopropyl/hydrogen (claims 3 and 5) or ethyl/ethyl (claim 6).
- The named species in claim 7 maps directly to the nitro + isopropyl/hydrogen slice: 6-Hydroxymethyl-2-isopropylaminomethyl-7-nitro-1,2,3,4-tetrahydroquinoline.
FAQs
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Does claim 7 extend beyond the nitro/isopropyl scope?
No. Claim 7 is the explicit species corresponding to the nitro branch with isopropyl/hydrogen amino substitution as reflected by claims 4 and 5.
-
Which dependent claims create the widest discrete chemical subsets?
Claims 2 (chloro with multiple fixed hydrogen positions) and 4 (nitro with the same hydrogen pattern). Claims 3, 5, and 6 narrow further by fixing R1/R2.
-
Is ethyl/ethyl coverage limited to the nitro branch?
Yes. The ethyl/ethyl assignment appears in claim 6, which depends on claim 4 (nitro).
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What is the most direct enforcement target visible in the excerpt?
The named compound in claim 7.
-
What single variable change would most directly fall outside these dependent claims?
Changing R5 away from nitro (claims 4-7) or away from chloro (claims 2-3), or changing any of the fixed hydrogen positions (R3/R6/R8).
References
[1] US Patent 3,821,228, claims 2-7 (as provided in the prompt).
