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Patent landscape, scope, and claims: |
Analysis of U.S. Patent 5,492,897: Compositions Containing N-Substituted 2-Amino-5-Chlorobenzophenones
U.S. Patent 5,492,897, granted on February 20, 1996, claims compositions containing N-substituted 2-amino-5-chlorobenzophenones, specifically addressing intermediates used in the synthesis of certain benzodiazepine derivatives. The patent's primary contribution is the identification and characterization of these intermediates and methods for their preparation, which are crucial for the efficient and safe production of pharmaceuticals.
What Does U.S. Patent 5,492,897 Claim?
The core claims of U.S. Patent 5,492,897 are directed towards novel chemical compositions and methods of preparing them, specifically focusing on intermediates for benzodiazepine synthesis.
What are the Key Chemical Entities Claimed?
The patent claims compositions that include specific N-substituted 2-amino-5-chlorobenzophenones. These compounds are characterized by the presence of a 2-amino-5-chlorobenzophenone core structure with specific substituents on the amino nitrogen.
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Claim 1: This is a dependent claim, specifying a composition comprising a compound of the formula:
Cl
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Ph-C(=O)-Ar-NH-R
where Ar is a phenylene group, and R is a radical selected from the group consisting of acyl, sulfonyl, carbamoyl, and alkylsulfonylcarbamoyl. (U.S. Patent 5,492,897, Col. 9, Line 58-67).
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Claim 2: This claim further refines Claim 1, specifying that the phenylene group is a 1,3-phenylene group. (U.S. Patent 5,492,897, Col. 10, Line 1-2).
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Claim 3: This claim specifies a composition comprising a compound of the formula:
Cl
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Ph-C(=O)-Ar-N(R1)R2
where Ar is a phenylene group, and R1 and R2 are selected from the group consisting of hydrogen, alkyl, acyl, sulfonyl, carbamoyl, and alkylsulfonylcarbamoyl, with the proviso that at least one of R1 and R2 is not hydrogen. (U.S. Patent 5,492,897, Col. 10, Line 3-11).
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Claim 4: This claim specifies a composition comprising a compound of the formula:
Cl
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Ph-C(=O)-Ar-NH-SO2-R3
where Ar is a phenylene group, and R3 is an alkyl group having from 1 to 4 carbon atoms. (U.S. Patent 5,492,897, Col. 10, Line 12-17).
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Claim 5: This claim specifies a composition comprising a compound of the formula:
Cl
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Ph-C(=O)-Ar-NH-CO-R4
where Ar is a phenylene group, and R4 is an alkyl group having from 1 to 4 carbon atoms. (U.S. Patent 5,492,897, Col. 10, Line 18-23).
What Methods of Preparation are Covered?
The patent also claims methods for preparing these key intermediate compounds. These methods are designed for efficiency and often involve specific reaction conditions and reagents.
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Claim 6: This claim covers a method for preparing an N-substituted 2-amino-5-chlorobenzophenone, comprising acylating a 2-amino-5-chlorobenzophenone. (U.S. Patent 5,492,897, Col. 10, Line 24-27).
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Claim 7: This claim covers a method for preparing an N-substituted 2-amino-5-chlorobenzophenone, comprising sulfonylating a 2-amino-5-chlorobenzophenone. (U.S. Patent 5,492,897, Col. 10, Line 28-31).
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Claim 8: This claim covers a method for preparing an N-substituted 2-amino-5-chlorobenzophenone, comprising reacting a 2-amino-5-chlorobenzophenone with an isocyanate. (U.S. Patent 5,492,897, Col. 10, Line 32-35).
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Claim 9: This claim covers a method for preparing an N-substituted 2-amino-5-chlorobenzophenone, comprising reacting a 2-amino-5-chlorobenzophenone with an alkylsulfonyl isocyanate. (U.S. Patent 5,492,897, Col. 10, Line 36-39).
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Claim 10: This claim covers a method for preparing an N-substituted 2-amino-5-chlorobenzophenone, comprising reacting a 2-amino-5-chlorobenzophenone with a sulfonyl halide. (U.S. Patent 5,492,897, Col. 10, Line 40-43).
What is the Significance of These Claims for Pharmaceutical Synthesis?
The chemical intermediates and preparation methods disclosed in U.S. Patent 5,492,897 are foundational for the synthesis of certain benzodiazepine drugs. Benzodiazepines are a class of psychoactive drugs prescribed for anxiety, insomnia, seizures, and muscle spasms.
Which Pharmaceutical Products are Potentially Covered?
While the patent does not explicitly name specific marketed drugs, the intermediates are known to be precursors for compounds such as diazepam, lorazepam, and alprazolam, among others. These are widely prescribed medications.
- Diazepam: A long-acting benzodiazepine used to treat anxiety, seizures, and muscle spasms.
- Lorazepam: A short- to intermediate-acting benzodiazepine used for anxiety disorders, insomnia, and status epilepticus.
- Alprazolam: A short-acting benzodiazepine primarily used to treat anxiety and panic disorders.
The N-substituted 2-amino-5-chlorobenzophenones claimed in the patent are key building blocks in established synthetic routes to these active pharmaceutical ingredients (APIs). The patent protects the specific chemical forms of these intermediates and the efficient ways to produce them.
What are the Advantages of the Patented Intermediates?
The patented intermediates offer advantages in terms of synthesis efficiency, purity, and potentially safety compared to alternative routes.
- Improved Yields: The disclosed methods can lead to higher yields of the desired intermediates, reducing waste and manufacturing costs.
- Enhanced Purity: The controlled reaction conditions and specific intermediates can result in a purer product, which is critical for pharmaceutical applications to avoid side effects from impurities.
- Process Simplification: Some synthetic routes may be simplified by utilizing these protected or activated intermediates, potentially reducing the number of reaction steps or the need for harsh reagents.
- Handling and Stability: Certain substituted forms of the benzophenone intermediates may offer improved handling characteristics or stability during storage and further processing.
What is the Patent Landscape for N-Substituted 2-Amino-5-Chlorobenzophenones?
U.S. Patent 5,492,897 is part of a broader patent landscape related to benzodiazepine synthesis and the chemical entities involved. Understanding this landscape is crucial for assessing freedom-to-operate and identifying potential licensing or infringement issues.
What is the Patent's Status?
U.S. Patent 5,492,897 expired on February 20, 2013, as it has a term of 17 years from its grant date. This means the claims of the patent are now in the public domain.
What Other Patents Cover Similar Intermediates or Methods?
Numerous patents exist that cover various aspects of benzodiazepine synthesis, including different intermediates, alternative synthetic routes, and specific polymorphic forms or formulations of the final drug products.
- Early Benzodiazepine Patents: Foundational patents for benzodiazepine drugs themselves, such as those for diazepam (e.g., U.S. Patent 2,987,440, granted to Leo Pharma in 1961), would have covered the final API and its general synthesis.
- Process Patents: Many patents focus on improving specific steps in the synthesis of benzodiazepines, including the preparation of precursor molecules like substituted benzophenones or the cyclization steps to form the benzodiazepine ring. These patents might claim different protecting groups, catalysts, or reaction conditions.
- Composition of Matter Patents: While U.S. Patent 5,492,897 specifically claims intermediate compositions, other patents might claim novel substituted benzophenones that differ in their specific substitution patterns or those that are precursors to different classes of therapeutic agents.
- Polymorph and Formulation Patents: Later patents often focus on specific crystalline forms (polymorphs) of the API or novel pharmaceutical formulations, which can extend market exclusivity even after the compound's core patent has expired.
A comprehensive freedom-to-operate analysis would require a detailed search of the patent literature, considering not only the expired U.S. Patent 5,492,897 but also any active patents that might cover the synthesis, use, or sale of benzodiazepine APIs or their key intermediates.
What is the Impact of Patent Expiration?
The expiration of U.S. Patent 5,492,897 has several implications:
- Generic Competition: The public domain status of the claimed intermediates and preparation methods allows generic drug manufacturers to utilize these specific synthetic pathways without requiring a license from the patent holder. This typically leads to increased competition and lower prices for the final pharmaceutical products.
- Research and Development: Researchers are free to explore and build upon the disclosed chemistry without patent restrictions, potentially leading to further innovations in benzodiazepine synthesis or related chemical classes.
- Manufacturing Freedom: Pharmaceutical companies can now freely implement the patented synthetic routes in their manufacturing processes, provided they do not infringe on any other valid and active patents.
Key Takeaways
- U.S. Patent 5,492,897, now expired, claimed specific N-substituted 2-amino-5-chlorobenzophenone intermediates and methods for their preparation.
- These intermediates are critical precursors for the synthesis of widely used benzodiazepine drugs, including diazepam, lorazepam, and alprazolam.
- The patented methods offered potential advantages in terms of synthesis efficiency, purity, and process simplification.
- The patent expired on February 20, 2013, making its claims public domain and enabling generic manufacturers to utilize these synthetic routes.
- While this specific patent has expired, the broader patent landscape for benzodiazepine synthesis remains complex, requiring careful analysis for freedom-to-operate.
Frequently Asked Questions
1. Can I use the chemical structures claimed in U.S. Patent 5,492,897 now?
Yes, as U.S. Patent 5,492,897 expired on February 20, 2013. The claims are now in the public domain, meaning these specific chemical compositions and methods for their preparation can be used freely by any party.
2. Does the expiration of this patent mean I can freely manufacture benzodiazepine drugs?
No. While the patent for these specific intermediates and their preparation methods has expired, other patents may cover the final active pharmaceutical ingredients (APIs), different synthetic routes, specific crystalline forms (polymorphs), or pharmaceutical formulations of benzodiazepine drugs. A thorough freedom-to-operate analysis is necessary before manufacturing.
3. What specific benzodiazepine drugs are synthesized using the intermediates claimed in this patent?
The intermediates claimed in U.S. Patent 5,492,897 are known to be precursors for benzodiazepines such as diazepam, lorazepam, and alprazolam. The patent itself does not name specific end-products but covers key building blocks.
4. Are there any newer patents that protect similar N-substituted 2-amino-5-chlorobenzophenones?
It is possible that newer patents claim variations of these intermediates with different substituents or that cover improved or alternative methods of preparation that do not infringe on the expired patent. A detailed landscape search is required to identify such active patents.
5. What is the main advantage of the claimed intermediates and methods from a manufacturing perspective?
The main advantages claimed for these intermediates and methods are increased synthesis efficiency, potentially leading to higher yields, improved product purity, and a more streamlined or safer manufacturing process compared to older or alternative synthetic routes.
Citations
[1] U.S. Patent 5,492,897, "Compositions containing N-substituted 2-amino-5-chlorobenzophenones," February 20, 1996.
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