Scope and claims deep-dive for US Patent 5,808,061: what the process covers, what it excludes, and how the US patent landscape stacks up

What is US Patent 5,808,061 protecting and what exactly do its claims cover?

US 5,808,061 is directed to a multi-step synthetic process for preparing compounds of “Formula I” (and pharmaceutically acceptable salts/solvates of those compounds), with key claim structure anchored on:

Building a substituted core from Formula II plus a bis-leaving-group reagent of the form Z–CH2–CH2–Z (Formula Z reagent).
Converting an intermediate of Formula IV (where Z is leaving group) into the target by nucleophilic substitution with nitrogen-containing cyclic amines.
Deprotecting hydroxy groups specifically at the “6- and 4′-positions”.
Optionally salt formation or solvate formation.

The claims also include product-by-intermediate coverage for Formula IV compounds (claims 13–15), where Z is a leaving group.

Inline reading of the independent claim structure shows three distinct layers of protection:

Process coverage (claims 1 and 9): two alternative routes to Formula I targets.
Narrower process dependents (claims 2–8): specify the R1/R2 polymethylene embodiment, hydrochloride salt, bromine leaving group, and single-vessel execution.
Intermediate/product coverage (claims 13–15): Formula IV with leaving group identity.

Claim 1 in plain scope terms

Claim 1 protects a process comprising:

Step a)
- React a Formula II compound with a Z–CH2–CH2–Z reagent (Z same or different leaving groups)
- React the resulting Formula IV intermediate (where Z is leaving group) with one of:
  - pyrrolidine
  - piperidine
  - hexamethyleneimine
  - methylpyrrolidine
  - dimethylpyrrolidine
  - morpholine
Step b) Deprotect hydroxy groups at positions 6 and 4′
Step c) Optionally form a salt or solvate

What Claim 1 requires (all must be met):

A substrate of Formula II
Reaction with a Z–CH2–CH2–Z homolog containing leaving groups on both ends
Formation of an intermediate of Formula IV where Z remains as leaving group
Substitution on Formula IV with one of the listed amines
Deprotection at the specified hydroxy positions
Optional salt/solvate stage does not need to occur to infringe, because it is “optionally” included

Claim 9 in plain scope terms

Claim 9 protects a different process route:

Step a) React Formula II with a Formula III compound (where R1 and R2 are as defined in Formula I)
Perform reaction using triphenylphosphine (PPh3) and diethyl azodicarboxylate (DEAD)
Step b) Deprotect the same 6- and 4′-hydroxy groups
Step c) Optional salification/solvate formation
Plus an added constraint: carried out in a single vessel

Claim 9 requires everything in steps a–c plus the “single vessel” limitation, and the specific reagents PPh3/DEAD for the coupling step.

Which variables in US 5,808,061 drive infringement risk: R1/R2 polymethylene, Z identity, amine selection, and deprotection?

US 5,808,061 hinges on four technical toggles that define whether a different synthesis “still lands inside” the claim language.

1) R1/R2 combinations: which polymethylene linkers are inside Formula I?

Claim 1 and Claim 9 define that R1 and R2 combine to form one of the following tether structures:

C4–C6 polymethylene
--CH2 CH(CH3)CH2 CH2 --
--CH2 C(CH3)2 CH2 CH2 --
--CH2 CH2 OCH2 CH2 --

Dependent claims narrow to explicit embodiments:

Claim 2: C4–C6 polymethylene
Claim 3: C5 polymethylene
Claim 10: C4–C6 polymethylene
Claim 11: C5 polymethylene

Practical implication for claim scope: the “C4–C6 polymethylene” language is a range, so many C4/C5/C6 linkers remain captured. Specific substituted linkers (isopropyl-like/tert-butyl-like motifs and the O-ether variant) appear captured only if they match the listed connectivity.

2) Z leaving group identity: bromo/halo coverage

Claim 6 requires “each Z is bromo.” Claim 5 also requires bromine in the context of the specific C4–C6 polymethylene dependent chain. Claim 13–15 cover Formula IV where:

Claim 14: leaving group is bromo, chloro, or iodo
Claim 15: leaving group is bromo

So there are two layers:

For the process claims, Z enters through the Z–CH2–CH2–Z reagent and the subsequent Formula IV intermediate.
For the intermediate claims, Z identity is explicitly limited to certain halogens.

3) Amines allowed in the substitution step (Claim 1)

Claim 1 allows substitution using one of six nucleophiles:

pyrrolidine
piperidine
hexamethyleneimine
methylpyrrolidine
dimethylpyrrolidine
morpholine

Any process using a different amine (for the Formula IV substitution step) is outside Claim 1, unless another independent claim (not provided here) covers it.

4) The 6- and 4′-hydroxy deprotection step (Claims 1 and 9)

Both independent claims require deprotection at two specific positions:

6-position
4′-position

Even if a competitor uses the same amination and same polymethylene linker, altering the protecting group strategy so that the hydroxy groups at those positions are not deprotected in the claimed sequence (or are deprotected to a different functional state) is a potential design-around, but only if the competing route can be structured to avoid meeting the literal step definition.

How broad are the independent process claims vs the dependent constraints?

Independent claim breadth (Claim 1)

Claim 1 is the broadest independent process claim in the excerpt because it does not require:

a specific Z identity (it only requires “same or different leaving group”),
a specific R1/R2 single embodiment beyond the Formula I-defined set,
hydrochloride salt,
single-vessel execution,
nor a specific coupling reagent set.

It does require the overall architecture: Formula II → Z–CH2–CH2–Z → Formula IV → amination with the listed amines → deprotection at positions 6 and 4′ → optional salt/solvate.

Independent claim breadth (Claim 9)

Claim 9 is narrower because it adds:

PPh3/DEAD in the coupling step (Step a)
Single vessel execution.

So Claim 1 likely sets the main infringement “net” for many competitor syntheses. Claim 9 captures a distinct process class where PPh3/DEAD coupling and single-vessel workflow are used.

Dependent claim sharpening

C4–C6 and C5: captured in claims 2–3 and 10–11.
Hydrochloride: claim 4 (dependent on claim 3), requiring the salt be hydrochloride.
Bromo-only Z: claims 5–6 and 15.
Single vessel: claims 7–8 and embedded in claim 9 itself.

These dependents are not substitutes; they narrow the routes and can be used to argue “multiple layers of coverage” depending on the fact pattern of the accused process.

What do claims 13–15 protect: intermediate compounds of Formula IV with leaving groups?

Claims 13–15 are directed to:

Claim 13: “A compound of formula IV wherein Z is a leaving group”
Claim 14: leaving group is bromo, chloro, or iodo
Claim 15: leaving group is bromo

This is intermediate-level product protection, not a process-only claim. That matters for litigation because a commercial manufacturer that sells or uses those intermediates in-house may face infringement theories tied to:

manufacture,
importation,
sale,
or use of the intermediate, depending on jurisdiction and enforcement posture.

Scope note: These intermediate claims are narrower than Claim 1’s process Z-flexibility because here Z is explicitly limited to the halo set.

Where is the key “design-around” leverage in the claim language?

US 5,808,061’s claim language suggests several factual “gate points” that can be targeted by alternate synthesis planning:

Avoid the exact amine nucleophile list for the Formula IV substitution step (Claim 1).
Change the deprotection logic so the process does not include deprotecting hydroxy groups at both the 6- and 4′-positions in the claimed manner/sequence.
Use a different linker strategy that yields Formula I structures without meeting the defined R1/R2 combination set (or makes R1/R2 outside the listed tether possibilities).
Use different coupling chemistry to escape Claim 9 (PPh3/DEAD) if the process otherwise matches Claim 1.
Avoid a single-vessel workflow if relying on Claim 9 exclusivity as an argument (though Claim 1 remains unaffected by the single-vessel language).

US 5,808,061 claims coverage map (structured)

Claim	Type	Core scope requirement	Key narrowing elements
1	Process (route A)	Formula II + Z–CH2–CH2–Z → Formula IV → amination with listed amines → deprotect 6 & 4′ → optional salt/solvate	No Z identity limit; no specific linker subtype beyond Formula I set; no single-vessel requirement
2	Process (dependent)	Claim 1	R1/R2 = C4–C6 polymethylene
3	Process (dependent)	Claim 2	R1/R2 = C5 polymethylene
4	Process (dependent)	Claim 3	Salt is hydrochloride
5	Process (dependent)	Claim 1	Each Z is bromo (and ties to Claim 1 via dependency chain)
6	Process (dependent)	Claim 1	Each Z is bromo
7	Process (dependent)	Claim 5	Single vessel
8	Process (dependent)	Claim 1	Single vessel
9	Process (independent, route B)	Formula II + Formula III in presence of PPh3/DEAD → deprotect 6 & 4′ → optional salt/solvate	Single vessel required
10	Process (dependent)	Claim 9	R1/R2 = C4–C6 polymethylene
11	Process (dependent)	Claim 10	R1/R2 = C5 polymethylene
12	Process (dependent)	Claim 11	Salt is hydrochloride
13	Intermediate/product	Formula IV where Z is leaving group	General leaving group term only
14	Intermediate/product	Claim 13	Z is bromo, chloro, or iodo
15	Intermediate/product	Claim 14	Z is bromo

What is missing for a complete US landscape and why that matters

A full “patent landscape” requires at minimum:

the patent’s full bibliographic record (application/priority dates),
the actual specification drawings and definition of Formula I/II/III/IV structures,
the complete claim set (beyond claims 1–15 provided),
and external references (family members, continuation patents, prosecution history, assignments, related Orange Book listings, and any litigation).

Those elements are not present in the provided input beyond the claim text excerpt. Without them, generating a credible, infringement-relevant map of:

expiration timing,
continuation/terminal disclaimer effects,
related method-of-use or formulation patents,
Paragraph IV or biosimilar challenges tied to the drug,
and competitor-specific route risks cannot be done accurately.

Key Takeaways

US 5,808,061 centers on process protection to make Formula I compounds through Formula II + Z–CH2–CH2–Z → Formula IV → substitution with a defined list of cyclic amines → deprotection of 6- and 4′-hydroxy groups → optional salt/solvate.
Claim 1 is the broad process net; Claim 9 is a narrower alternative route requiring PPh3/DEAD and single-vessel operation.
Z leaving group identity becomes a tighter constraint in dependents (notably bromo) and in intermediate claims 13–15 (bromo/chloro/iodo; then bromo).
The deprotection positions (6 and 4′) and the allowed amines are the most direct factual gate points for infringement analysis and design-around planning.

FAQs

Which specific amines in US 5,808,061 are permitted for the Formula IV substitution step?
Does US 5,808,061 require hydrochloride salt formation to infringe?
How does the “single vessel” limitation change infringement risk between claims 1 and 9?
Are intermediates of Formula IV covered as standalone infringable products in US 5,808,061?
How does changing Z from bromo to chloro or iodo affect coverage for the process vs the intermediate claims?

References

US Patent 5,808,061. Claims excerpt as provided in the prompt.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	2145614	⤷ Start Trial
European Patent Office	0675121	⤷ Start Trial
Japan	H07278138	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,808,061

Summary for Patent: 5,808,061