Mixed Anhydride Peptide Coupling for Sterically Bulky Amino Acids
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Solution Overview
Problem
Existing peptide synthesis methods for commercial scale production are expensive due to the high cost of activators like O-(1H-Benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HTBU), and lower cost activators often result in slow reactions or undesirable racemization when sterically bulky amino acids are involved.
Innovation Solution
The use of a mixed anhydride compound of Formula (I) for peptide synthesis, which includes a sterically bulky tri-tert-butyl-tryptophan residue, allows for fast and selective amide bond formation with amino acids or peptides, reducing epimerization and enabling efficient commercial-scale production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lower cost activators are used for peptide coupling, then manufacturing cost is reduced, but reaction rate decreases and racemization increases
Solution Approach 1:
The patent changes the chemical structure parameters of the activator by using mixed anhydrides with specific acyl groups (pivaloyl, isobutyryl, or isopropylcarbonyl) instead of conventional activators. This structural modification enables the activator to maintain high reactivity with sterically hindered amino acids while being cost-effective, thus resolving the contradiction between cost reduction and reaction rate maintenance.
2Productivity
If conventional activators are used with sterically bulky amino acids, then coupling can proceed, but selectivity decreases due to attack on undesired carbonyl group
Solution Approach 1:
The patent applies local quality by designing the mixed anhydride activator with specific acyl groups that create a sterically differentiated environment around the carbonyl groups. The bulkier acyl group (pivaloyl, isobutyryl, or isopropylcarbonyl) provides steric shielding to one carbonyl, making the other carbonyl more accessible and selective for nucleophilic attack by the amino group, thus improving selectivity while maintaining coupling efficiency.
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
The method provides yields suitable for commercial processes by facilitating quick and selective reactions despite the high steric bulk of the tri-tert-butyl-tryptophan side chain, thereby reducing undesirable epimerization and simplifying purification.
Implementation Method 1
The reaction between the mixed anhydride compound of Formula (I) and the second moiety may form the target peptide or a precursor to the target peptide... involves the carbonyl closest to the tri-tert-butyl-tryptophan (Tbt) side chain... results in the formation of an amide bond
Data Source
Figure 1
Figure 2A
Figure 2A
AI summary
The invention is directed to a method of making a target peptide comprising reacting a mixed anhydride compound of Formula (I) with a second moiety which is an amino acid or peptide, wherein Formula (I) has the following structure: Formula (I) and wherein R1-R3 are as defined in the disclosure.