Chiral Iridium Asymmetric Hydrogenation for Tocopherol Synthesis
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Solution Overview
Problem
There is a strong need for an effective and industrial-scale synthesis of (2R,4'R,8'R)-tocopherols and (R,R)-isophytol, as natural sources are limited, and higher bioactivity is associated with the R-configuration at specific chiral centers in these molecules.
Innovation Solution
A process involving the asymmetric hydrogenation of (6R,10R)-6,10,14-trimethylpentadecan-2-one is developed, which includes the separation and cis/trans isomerization of isomers from a mixture of 6,10,14-trimethylpentadeca-5,9,13-trien-2-one or 6,10,14-trimethylpentadeca-5,9-dien-2-one, using a chiral iridium complex and specific additives to achieve high-quality production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If asymmetric hydrogenation is performed on a mixture of stereoisomers, then the production efficiency is improved, but the manufacturing precision of the desired chiral product deteriorates
Solution Approach 1:
The patent applies preliminary action by performing cis/trans isomerization before asymmetric hydrogenation. The mixture of stereoisomers is first isomerized to enrich the desired (E,E) and (Z,Z) isomers, which are then selectively hydrogenated. This preliminary isomerization step ensures that when hydrogenation occurs, the dominant substrates are the ones that will produce the desired (6R,10R) product, thus maintaining high chiral purity while processing the entire mixture efficiently
Solution Approach 2:
The patent utilizes parameter changes by employing specific reaction conditions including catalyst selection (chiral catalysts with specific configurations), temperature control, and pressure parameters during asymmetric hydrogenation. By optimizing these parameters, the process achieves high enantioselectivity (er > 98:2) while maintaining high conversion rates, thus resolving the contradiction between productivity and manufacturing precision
2Manufacturing precision
If separation of individual isomers is performed before asymmetric hydrogenation, then the manufacturing precision is improved, but the productivity deteriorates
Solution Approach 1:
The patent applies the taking out principle by selectively removing or focusing on the valuable (E,E) and (Z,Z) isomers through isomerization, while the unwanted isomers are converted into the desired configuration. Rather than separating and discarding unwanted isomers, the process extracts and utilizes the valuable stereoisomers after isomerization, converting the entire mixture into useful material for the asymmetric hydrogenation step
Solution Approach 2:
The patent merges multiple operations into an integrated process flow where isomerization and asymmetric hydrogenation are combined in sequence. Instead of separate purification steps followed by reaction, the process combines isomerization (which enriches desired isomers) with subsequent hydrogenation, allowing the entire mixture to be processed efficiently while achieving high product purity
3Loss of substance
If cis/trans isomerization is used to utilize non-desired isomers, then the loss of substance is reduced, but the device complexity increases
Solution Approach 1:
The patent applies the blessing in disguise principle by converting the unwanted stereoisomers (which would normally be waste or require costly separation) into valuable substrates through cis/trans isomerization. The non-desired isomers are transformed into the desired (E,E) and (Z,Z) configurations, which then participate efficiently in asymmetric hydrogenation. This converts what would be harmful waste into beneficial material, achieving near 100% utilization of all starting material
Solution Approach 2:
The patent uses cis/trans isomerization as an intermediary step that mediates between the mixed stereoisomer starting material and the asymmetric hydrogenation reaction. This intermediary process enriches the desired isomers and prepares the mixture for efficient hydrogenation, acting as a bridge that enables complete utilization of all starting materials while maintaining high product purity
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 process efficiently produces the desired chiral product from stereoisomers, enabling industrial-scale production of (2R,4'R,8'R)-tocopherols and (R,R)-isophytol with improved bioactivity, utilizing the R-configuration at key chiral centers.
Implementation Method 1
asymmetric hydrogenation of either 6,10,14-trimethylpentadeca-5,9,13-trien-2-one or 6,10,14-trimethylpentadeca-5,9-dien-2-one or a ketal of 6,10,14-trimethylpentadeca-5,9,13-trien-2-one or 6,10,14-trimethylpentadeca-5,9-dien-2-one using molecular hydrogen in the presence of a chiral iridium complex
Implementation Method 2
asymmetric hydrogenation of either 6,10,14-trimethylpentadeca-5,9,13-trien-2-one or 6,10,14-trimethylpentadeca-5,9-dien-2-one or a ketal of 6,10,14-trimethylpentadeca-5,9,13-trien-2-one or 6,10,14-trimethylpentadeca-5,9-dien-2-one using molecular hydrogen in the presence of a chiral iridium complex
Implementation Method 3
separating individually the (5E,9E)- and/or the (5Z,9Z)-isomer of 6,10,14-trimethylpentadeca-5,9,13-trien-2-one or 6,10,14-trimethylpentadeca-5,9-dien-2-one from the mixture of step a)
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
The present invention relates to a process of manufacturing (6R,10R)- 6,10,14-trimetylpentadecan-2-one in a multistep synthesis from a mixture of (5E,9E)-, (5E,9Z)-, (5Z,9E)- and (5Z.9Z)- isomers of 6, 10, 14-trimetylpentadeca- 5,9,13-trien-2-one or 6,10,14-trimetylpentadeca-5,9-dien-2-one. The process is very advantageous in that it forms in an efficient way the desired chiral product from a mixture of stereoisomers of the starting product.