Crystallization of 25-Hydroxy-7-dehydrocholesterol Purification
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Solution Overview
Problem
The existing methods for synthesizing 25-hydroxy-vitamin D3 are plagued by high levels of impurities, specifically 3β-Cholesta-5,7,22-triene-3,25-diol, which are difficult to separate due to their similar physical properties, leading to contamination in the final product.
Innovation Solution
A crystallization process using a solvent system comprising ethanol, 1-propanol, or 2-propanol, with a minimum 50% weight percentage, effectively separates 25-Hydroxy-7-dehydrocholesterol from its impurity by exploiting differences in their solubility and crystallization behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional synthesis methods are used to produce 25-hydroxy-vitamin D3, then the production process can proceed, but high levels of impurities (3β-Cholesta-5,7,22-triene-3,25-diol) remain difficult to separate
Solution Approach 1:
The patent applies parameter changes by modifying the physical state and solubility characteristics of the compounds through controlled crystallization. By adjusting temperature, solvent composition, and crystallization conditions, the method exploits subtle differences in solubility parameters between compound (I) and impurity (II) to achieve separation. This transforms the separation problem from a complex multi-step process into a controlled phase transition process.
Solution Approach 2:
The core invention utilizes phase transitions through crystallization. Compound (I) is induced to crystallize from solution while impurity (II) remains in the mother liquor. The phase transition from dissolved state to crystalline solid state allows for physical separation via filtration, effectively removing the impurity without requiring complex separation equipment or multiple processing steps.
2Manufacturing precision
If repetitive reduction reaction cycles are used as disclosed in US 4,116,985, then cholesta-5,7-diene-3β-25-diol can be isolated, but the process becomes very laborious and expensive
Solution Approach 1:
The invention applies preliminary action by performing crystallization early in the synthesis pathway, immediately after the formation of compound (I). This single preliminary purification step removes impurity (II) before subsequent photochemical reactions, preventing impurity propagation throughout the entire synthesis sequence. This eliminates the need for repetitive reduction cycles performed in prior art.
Solution Approach 2:
The method extracts impurity (II) from the reaction mixture through selective crystallization of compound (I). By exploiting solubility differences, the impurity is left in the mother liquor while the desired compound crystallizes out. The crystallized product is then separated by filtration, effectively extracting the pure compound from the impure reaction mixture in a single operation.
3Productivity
If compound of formula (II) is present in high amounts, then the synthesis can proceed, but the impurity is transformed analogously to an impurity in the targeted end product HyD
Solution Approach 1:
The invention applies preliminary anti-action by removing impurity (II) through crystallization before the photochemical transformation step. This preemptive purification prevents the impurity from being converted into unwanted byproducts in the final product. By eliminating the impurity source early, the method ensures high purity in the end product without requiring additional purification steps after photochemical reaction.
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 significantly reduces the impurity levels in 25-Hydroxy-7-dehydrocholesterol, achieving purities of less than 0.07% by weight in a single crystallization step, with further recrystallization cycles enhancing purity while maintaining high yields.
Implementation Method 1
A crystallization using a unique solvent system can offer a solution to said problem... exploiting differences in their solubility and crystallization behavior
Implementation Method 2
crystallization of compound of formula (I) from a composition comprising the compound of formula (I) and the compound of formula (II)
Data Source
AI summary
The present invention relates to a method of purification of compound of formula (I) which comprises the step of crystallization of compound of formula (I) from a composition comprising the compound of formula (I) and the compound of formula (II) and a specific solvent system containing ethanol, 1-propanol, 2-propanol, 2-methyl-1-propanol, 1-butanol or 2-butanol.