Scope, Claims, and Patent Landscape of U.S. Patent 4,935,437
Overview
U.S. Patent 4,935,437, granted on June 19, 1990, to Eli Lilly and Company, covers a process for preparing 2,6-dimethoxyphenol derivatives. It is primarily relevant in the context of pharmaceutical synthesis, with claims centered on chemical processes directed towards specific compounds used in drug development. This patent resides within the broader landscape of phenolic compound synthesis, particularly related to agents with potential pharmaceutical applications.
What Are the Central Claims of U.S. Patent 4,935,437?
Primary Focus
The patent claims a process for synthesizing 2,6-dimethoxyphenol derivatives via specific chemical steps. Key features include:
- Starting from chlorophenols with defined substitution patterns.
- Employing a methylation step involving dimethyl sulfate or methyl iodide.
- Using mild reaction conditions to obtain the desired phenolic compounds with high purity.
- The process encompasses specific reagent ratios, solvents, and temperature ranges.
Claim Breakdown
The patent contains 4 claims, with the core claim — Claim 1 — covering:
- A method of preparing 2,6-dimethoxyphenol derivatives.
- The process involving methylation of chlorophenols.
- Use of particular reagents (e.g., dimethyl sulfate, methyl iodide).
- Reaction temperatures within 0°C to 100°C.
- Reaction in solvent media such as acetone or methanol.
Dependent claims specify alternative reagents, solvents, and reaction conditions, broadening the scope of potential process variations.
Patent Scope and Novelty
Scope
The claims emphasize the synthesis process rather than the final compound. The process focuses on achieving high yield and purity while minimizing side reactions. The patent's claims do not extend to the final drug molecules but cover the chemical methods to produce the key intermediates.
Novelty and Inventive Step
At the time of filing (1988), the process introduced a milder, more efficient methylation route compared to prior art, which often involved harsher conditions or less selective methylating agents. The process's novelty lies in the optimized methylation step under specific reaction conditions, which improved yield and product purity.
Patent Landscape and Related Art
Pre-Existing Art
Prior patents and literature existed on phenol derivative synthesis, notably:
- U.S. Patent 4,622,359 (1986) on phenolic synthesis.
- Organic synthesis literature discussing methylation with dimethyl sulfate.
Post-Grant Art & Litigation
The patent has been cited in subsequent patent applications related to phenolic compounds, particularly in the development of antidepressant and anti-inflammatory agents. Despite its age, the patent's process claims have had limited litigation activity, primarily serving as prior art during later patent challenges.
Patent Lifecycle and Status
Expiration
Filed as a utility patent, it expired on June 19, 2007, after a 20-year term from the grant date, with no extensions or patent term adjustments applicable.
Current Patent Landscape
The expired status leaves freedom for multiple parties to develop derivatives or improved processes without infringement concerns. Recent activity includes filings for protective formulations and novel therapeutics based on phenolic intermediates.
Implications for Pharmaceutical Development
- Intermediates: The process applies to the synthesis of intermediates used in active pharmaceutical ingredients (APIs) for drugs targeting various therapeutic areas.
- Freedom-to-Operate: Post-expiration, manufacturers can freely synthesize similar phenolic intermediates using alternative processes.
- Design-around Strategies: Competitors have developed alternative methylation methods, such as using methyl triflate or methyl bromide, to circumvent the patented process.
Key Takeaways
- U.S. Patent 4,935,437 claims a specific methylation process for phenolic derivatives.
- The patent's scope is limited to process claims, not the compounds themselves.
- The patent was filed in 1988, granted in 1990, and expired in 2007.
- The process introduced milder, more efficient methylation techniques compared to prior art.
- The patent landscape includes subsequent applications and derivatives, but no major litigation appears documented.
- Post-expiration, the process can be freely employed, supporting further development of phenol-based pharmaceuticals.
FAQs
Q1: What specific chemical process is patented in U.S. Patent 4,935,437?
A1: It covers the methylation of chlorophenol compounds using reagents like dimethyl sulfate or methyl iodide under controlled conditions to produce 2,6-dimethoxyphenol derivatives.
Q2: How does this patent influence current synthesis of phenolic drugs?
A2: Since it expired in 2007, it no longer restricts synthesis. It previously provided a foundation for efficient methylation techniques in phenolic compound manufacturing.
Q3: Are there existing alternatives to the patented process?
A3: Yes. Post-1990, methylation using alternative reagents such as methyl triflate and other methylating agents have been developed to achieve similar outcomes.
Q4: Did the patent cover therapeutic compounds or just processes?
A4: It covered only process claims, not the final therapeutic compounds themselves.
Q5: Has U.S. Patent 4,935,437 been involved in litigations or patent challenges?
A5: There is no documented evidence of major litigation. It has been cited as prior art in later patent applications.
References
- U.S. Patent 4,935,437.
- Organic synthesis literature on phenolic methylation.
- Patent citation databases and legal records.
