Hyperpolarized Carboxylate Preparation via Unsaturated Ester PHIP
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Solution Overview
Problem
The existing ParaHydrogen Induced Polarization (PHIP) technique faces limitations in preparing 13C-hyperpolarized carboxylate molecules of diagnostic interest due to the scarcity of suitable unsaturated molecular precursors and instability issues, such as keto-enol tautomerism, which restricts the application of these molecules in Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS).
Innovation Solution
A PHIP-based process using unsaturated esters, specifically alkenyl or alkynyl esters, as hydrogenable substrate precursors to prepare [1-13C]-hyperpolarized carboxylate molecules, where para-hydrogenation induces polarization transfer to the 13C signal of the carboxylate carbon atom, followed by removal of the hydrogenated group to obtain the desired hyperpolarized carboxylate or carboxylic acid in an aqueous solution, overcoming the limitations of traditional Dynamic Nuclear Polarization (DNP) methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional Dynamic Nuclear Polarization (DNP) method is used to prepare hyperpolarized carboxylate molecules, then polarization can be achieved, but the process requires sophisticated and expensive equipment and long polarization cycles of about 1 hour
Solution Approach 1:
The patent changes the fundamental parameter of the hyperpolarization mechanism from electron-nuclear spin transfer (DNP) to parahydrogen-induced polarization. This involves using para-hydrogen gas as a reagent that adds across double bonds in unsaturated carboxylate precursors, transferring spin polarization directly to the carbon nuclei during the chemical reaction itself, thereby eliminating the need for complex DNP equipment and reducing polarization time
Solution Approach 2:
The patent replaces the mechanical/physical DNP system (requiring cryogenic temperatures, high magnetic fields, and microwave irradiation) with a chemical system based on parahydrogen addition. The hyperpolarization is achieved through a chemical reaction mechanism rather than a physical field-based mechanism, substituting complex equipment with a simpler chemical approach
2Productivity
If PHIP technique is applied to prepare 13C-hhyperpolarized carboxylate molecules, then faster polarization can be achieved, but suitable unsaturated molecular precursors are scarce and suffer from instability issues such as keto-enol tautomerism
Solution Approach 1:
The patent introduces an intermediary ester group that connects the carboxylate functionality to the unsaturated double bond. The ester linkage acts as a stabilizing mediator that prevents direct interaction between the carbonyl group and the double bond, thereby eliminating keto-enol tautomerism while still allowing para-hydrogen addition to occur at the vinyl group. This intermediary structure enables both fast PHIP polarization and molecular stability
Solution Approach 2:
The patent performs preliminary chemical modification by converting the carboxylate molecule into an unsaturated ester precursor before applying PHIP. This preliminary action of esterification with a vinyl or allyl group prepares the molecule in advance to be stable during storage and handling, while the unsaturated group is positioned to receive para-hydrogen addition for hyperpolarization
3Productivity
If unsaturated precursors are used for PHIP, then hyperpolarization can be achieved, but the precursors suffer from keto-enol tautomerism instability
Solution Approach 1:
The ester group serves as a protective intermediary that spatially and electronically separates the carbonyl oxygen from the vinyl double bond. This intermediary structure prevents the proton transfer mechanism that causes keto-enol tautomerism, while maintaining the unsaturation necessary for para-hydrogen addition and subsequent hyperpolarization of the carboxylate carbon
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 approach allows for the convenient preparation of [1-13C]-hyperpolarized carboxylate molecules with good yield and polarization degree, enabling their use as MR probes in vascular imaging, perfusion mapping, and metabolic pathway studies, providing enhanced sensitivity and stability for diagnostic applications.
Implementation Method 1
A PHIP-based process using unsaturated esters, specifically alkenyl or alkynyl esters, as hydrogenable substrate precursors to prepare [1-13C]-hyperpolarized carboxylate molecules, where para-hydrogenation induces polarization transfer to the 13C signal of the carboxylate carbon atom
Implementation Method 2
hydrogenating with molecular para-hydrogen an unsaturated alkenyl or alkynyl ester of the concerned carboxylate molecule
Data Source
AI summary
The present invention relates to a process for the preparation of aqueous solutions of [1-13C]-hyperpolarized carboxylate containing molecules of diagnostic interest that comprises parahydrogenating with molecular parahydrogen unsaturated alkenyl or alkynyl esters of the concerned 13C-carboxylate molecules.