Benzoxaborole Synthesis via Modular Deprotection
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Solution Overview
Problem
Current methods for preparing benzoxaboroles, particularly their pharmaceutically acceptable salts, lack efficient and alternative processes for producing antibacterial agents effective against Gram-negative pathogens.
Innovation Solution
A multi-step process involving deprotection, nitromethane reaction, reduction, borylation, and enantioselective reduction to synthesize compounds like (3S)-3-(aminomethyl)-7-[(3-hydroxypropyl)oxy]-2,1-benzoxaborol-1(3H)-ol hydrochloride, utilizing various reagents and conditions to achieve the desired antibacterial agent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current methods for preparing benzoxaboroles are used, then the antibacterial agent can be produced, but the process lacks efficiency and alternative pathways
Solution Approach 1:
The patent divides the synthesis process into distinct modular steps: forming the benzoxaborole core structure, introducing the hydroxypropyl side chain via Williamson ether synthesis, and final deprotection. This segmentation allows each step to be optimized independently and enables alternative synthetic pathways to be explored for different intermediates.
Solution Approach 2:
The patent employs universal reagents and conditions that can be applied across multiple synthesis steps and variations. For example, sodium hydride is used as a base in Williamson ether synthesis, and various deprotection conditions (acidic, basic, enzymatic) are provided as interchangeable options, making the overall process adaptable to different starting materials and desired products.
2Manufacturing precision
If deprotection is performed under standard conditions, then the compound of formula A is formed, but the process may lack selectivity or require harsh conditions
Solution Approach 1:
The patent provides multiple deprotection methodologies with varying parameters: acidic conditions (pH control), basic conditions (pH control), enzymatic conditions (temperature and pH optimization), and hydrogenolysis (pressure and catalyst selection). By changing these parameters, selective deprotection can be achieved under milder, more specific conditions appropriate for different protecting groups and substrate sensitivities.
Solution Approach 2:
The patent introduces intermediates with specific protecting groups that can be selectively removed. For example, benzyl protecting groups can be removed via hydrogenolysis using palladium catalysts, while other groups like acetyl or benzoyl can be removed under basic or enzymatic conditions. This intermediary approach allows selective deprotection without harsh conditions affecting the entire molecule.
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 provides an efficient method for producing benzoxaboroles and their salts, enhancing their antibacterial efficacy against Gram-negative pathogens and offering flexibility in synthesis.
Implementation Method 1
deprotecting a compound of formula 6: or a pharmaceutically acceptable salt thereof; under deprotecting conditions to form a compound of formula A: or a pharmaceutically acceptable salt thereof
Implementation Method 2
reducing the nitro group to an amine group
Implementation Method 3
contacting the compound of formula 5 or a salt thereof with a borylating reagent characterized by the following formula: in the presence of n-BuLi, to form a compound of formula 6
Implementation Method 4
The compound of formula 10 or a salt thereof can be prepared by enantioselective reduction of a compound of formula 10: or a salt thereof
Implementation Method 5
brominating a compound of formula 8: to form a compound of formula 9: where R is H or OR 1
Data Source
AI summary
The present invention is a process comprising contacting a compound of formula 6: or a pharmaceutically acceptable salt thereof; with a deprotecting reagent to form a compound of formula A: or a pharmaceutically acceptable salt thereof; where R is H or OR1; R1 and each R1' are protecting groups; R1 " is H or OH, and n is 0, 1, 2, 3, 4, or 5.