Fmoc Solid-Phase Peptide Synthesis Preventing Hydantoin Rearrangement
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Solution Overview
Problem
The synthesis of degarelix, a synthetic decapeptide used in treating prostate cancer, faces contamination issues due to the rearrangement of the dihydrouracil moiety to a hydantoin moiety under basic conditions, making it difficult to achieve pharmaceutical-grade purity without substantial loss of product, and existing methods using tert-butyloxy-carbonyl (Boc) protection groups pose hazards to human health and the environment.
Innovation Solution
The method employs solid-phase peptide synthesis using fluorenylmethyloxycarbonyl (Fmoc) as the α-amino protecting group, allowing for step-wise coupling and deprotection under basic conditions without rearrangement of the Aph(L-Hor) moiety, ensuring purity and safety by using organic bases like piperidine, and including side-chain protection to prevent side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If basic conditions are employed in peptide synthesis, then deprotection of Fmoc group is achieved, but rearrangement of dihydrouracil moiety to hydantoin occurs causing contamination
Solution Approach 1:
The patent changes the chemical parameters of the base reagent from traditional strong bases (NaOH, K2CO3) to organic bases (piperidine, NMM, DBU) with different basicity characteristics. This parameter change allows deprotection to proceed while preventing the rearrangement reaction, achieving both efficient deprotection and high product purity without requiring additional purification steps
2Ease of manufacture
If Boc protecting group is used, then synthesis can proceed under acidic conditions, but human health and environment are hazardous due to TFA toxicity
Solution Approach 1:
The patent changes the protecting group system from Boc (acid-labile) to Fmoc (base-labile), fundamentally altering the chemical parameters of the synthesis conditions. This enables the use of organic bases instead of toxic TFA, maintaining synthesis feasibility while eliminating the harmful effects of trifluoroacetic acid on human health and the environment
3Manufacturing precision
If separation of hydantoin by-product is attempted, then impurity removal is achieved, but substantial loss of product occurs
Solution Approach 1:
The patent applies preliminary anti-action by selecting organic bases that prevent the rearrangement reaction from occurring in the first place. By using bases like piperidine, NMM, or DBU under controlled conditions, the dihydrouracil moiety is protected from converting to the hydantoin form, thereby preventing impurity formation before it can compromise product purity or require separation that would cause yield loss
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 results in pharmaceutically pure degarelix with less than 0.3% impurity, reducing hazards to human health and the environment, and lowering production costs while maintaining high yield and product integrity.
Implementation Method 1
removing Fmoc by contacting the support with an organic base in an organic solvent
Implementation Method 2
contacting the support with the solution in the presence of reagent for forming a peptide bond between a carboxyl group of the dissolved amino acid or peptide and the amino group linked to the support
Data Source
AI summary
In a step-wise synthesis of degarelix comprising 0.3% by weight or less of 4-([2-(5-hydantoyl)]acetylamino)-phenylalanine analog on (solid support)-NH2 a step comprises providing a solution of an amino acid or peptide of which the α-amino group is protected by Fmoc; contacting the support with the solution in the presence of reagent for forming a peptide bond between a carboxyl group of the amino acid or peptide and (solid support)-NH2; removing Fmoc by contacting the support with an organic base, in particular piperidine, in an organic solvent. Also disclosed is degarelix of high purity prepared by the method of the invention and the use of Fmoc in the synthesis of degarelix.