Ciclesonide Synthesis via Safe Acid Catalysis
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Solution Overview
Problem
Current methods for synthesizing ciclesonide are not designed for large-scale industrial production, pose safety hazards due to the use of explosive substances like perchloric acid, and are inefficient in terms of resource usage and epimer purification.
Innovation Solution
A process using a stable salt of isobutyric acid, avoiding perchloric acid and nitroalkanes, and employing regioselective bromination and crystallization to achieve high yields and purity of ciclesonide, specifically through the reaction of 21-bromo-16α,17-cyclohexylmethylenedioxy-11β-hydroxypregna-1,4-dien-3,20-one, with polar solvents like dimethylsulphoxide and N-methyl-2-pyrrolidone, and subsequent crystallizations from alcoholic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If perchloric acid is used as catalyst for the reaction of 11β,16α,17,21-tetrahydroxypregna-1,4-dien-3,20-one with cyclohexane aldehyde, then the reaction proceeds to form 16α,17-[(R,S)-cyclohexylmethylenedioxy]-11β,21-dihydroxy-pregna-1,4-dien-3,20-one, but the process becomes hazardous due to the explosive nature of perchloric acid requiring stringent safety precautions and increasing costs
Solution Approach 1:
The patent replaces the hazardous, expensive-to-handle perchloric acid with a safer, less hazardous acid catalyst that can be used without stringent safety precautions. This substitution maintains reaction efficiency while eliminating the safety hazards associated with perchloric acid storage, handling, and disposal
Solution Approach 2:
The patent introduces an intermediary substance (a safer acid catalyst) to mediate the reaction between 11β,16α,17,21-tetrahydroxypregna-1,4-dien-3,20-one and cyclohexane aldehyde. This intermediary performs the same catalytic function as perchloric acid but without the explosive hazards, allowing the reaction to proceed efficiently while maintaining safety
2Manufacturing precision
If multiple fractional crystallisations are performed to concentrate the R epimer from 16α,17-[(R,S)-cyclohexylmethylenedioxy]-11β,21-dihydroxy-pregna-1,4-dien-3,20-one, then the epimeric purity increases to ≥ 97%, but the process complexity and number of steps increase significantly
Solution Approach 1:
The patent performs preliminary action by optimizing the initial reaction conditions (catalyst selection, temperature, stoichiometry) to favor the formation of the R epimer from the start. This preliminary optimization reduces the need for subsequent purification steps, achieving high epimeric purity with fewer crystallization steps
Solution Approach 2:
The patent applies parameter changes by modifying reaction parameters (acid catalyst type, temperature, solvent system) to directly influence the epimer ratio formed during the ketalization reaction. By changing these parameters, the process achieves high R epimer concentration in the crude product, eliminating the need for multiple fractional crystallizations
3Manufacturing precision
If four successive crystallisations from ethanol/water are performed to achieve R epimer proportion > 99.5%, then the epimeric purity is maximized, but the total yield decreases to approx. 50% due to material loss in each step
Solution Approach 1:
The patent performs preliminary action by designing the reaction to inherently produce high R epimer selectivity (R/S > 90:10) through optimized catalysis and reaction conditions. This preliminary selectivity minimizes the amount of S epimer that would otherwise require removal through multiple crystallization steps, thereby preserving material and maintaining high yield
Solution Approach 2:
The patent converts the potential harm of epimer formation into a benefit by using reaction conditions that selectively favor R epimer formation. The presence of acid catalyst and controlled temperature transforms what could be a mixture into a selectively enriched product, turning the crystallization process from a purification necessity into a minor final step
4Manufacturing precision
If large amounts of solvent are used for crystallisation to improve R/S epimer ratio, then the purification effectiveness increases, but the solvent consumption and resource usage increase significantly
Solution Approach 1:
The patent performs preliminary action by optimizing the reaction to produce high R epimer selectivity before crystallization. This preliminary enrichment means that fewer crystallization steps with less solvent are needed to achieve the desired final purity, significantly reducing solvent consumption
Solution Approach 2:
The patent applies parameter changes by modifying the crystallization parameters (temperature profile, solvent composition, addition rate) to maximize purification efficiency per unit of solvent. By changing these parameters, the process achieves high epimer ratio improvement with minimal solvent usage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the safe, efficient, and scalable production of epimerically pure ciclesonide with high total yield, reducing the need for hazardous materials and minimizing solvent usage while achieving a high R epimer concentration.
Implementation Method 1
acid-catalysed reaction of 11β,16α,17,21-tetrahydroxypregna-1,4-dien-3,20-one with cyclohexane aldehyde
Implementation Method 2
concentrated by evaporation
Implementation Method 3
purified by crystallisation from solvent
Data Source
AI summary
The invention relates to a process for preparing ciclesonide in epimerically pure form, a corticosteroid of formula 1: Ciclesonide is used for the treatment of respiratory complaints.