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Faster Coupling: Improved Purity with Less Epimerization Coupling with carbodiimide chemistry has significant benefits over aminium/phosphonium salts (ex. HATU, HCTU, PyBOP) at elevated temperature. This includes major reductions of epimerization for cysteine and γ-lactam formation of arginine. However, activation by carbodiimides is relatively slow. We developed an improved coupling process which allows for faster formation of the key O-acylisourea intermediate by increasing the amount of carbodiimide to 2 equivalents relative to the amino acid.1 By forming more activated amino acid faster than standard carbodiimide chemistry the subsequent coupling will happen quicker. This provides not only a faster coupling time, but also less epimerization from less time as a sensitive activated amino acid. This methodology termed CarboMAX is patent pending and exclusively licensed for use on CEM’s peptide synthesizers.

Reduced Epimerization (ex. Liraglutide)

Improved Purity

Unparalleled speed and efficiency
Traditional solid phase peptide synthesis involves the use of iterative and separate deprotection and coupling steps with washing in-between. This is based on the assumption that undesirable amino acid insertions can occur without complete draining and washing between each step. In 2013, it was demonstrated that washing after the coupling step can be eliminated without effect on peptide purity. ¹

The Liberty PRIME™ takes this further by using a new onepot coupling and deprotection process. ² This technique involves addition of the deprotection reagent (base) directly to the undrained post-coupling mixture. The ability to do this is based on the insight that faster reaction kinetics in the solution phase promote rapid hydrolysis or selfcondensation of the active ester, thereby avoiding potential side reactions at the resin bound amino functionality. The Fmoc removal then proceeds uninterrupted at elevated temperature. An optimized use of reagents results in an essentially neutral reaction mixture towards the end of deprotection step. This new procedure offers several advantages such as (a) approximately 90% reduction in solvent requirement for the deprotection step, (b) 75% reduction in solvent requirement for post-deprotection washings, (c) faster deprotection step since the microwave ramp time is not needed, and (d) shorter cycle time due to absence of post-coupling drain step.

Utilization of the one-pot coupling/deprotection methodology requires the ability to consistently add precise small volumes of concentrated base. To achieve this, the Liberty PRIME™ incorporates a new dedicated pumping module with the ability to rapidly add the deprotection reagent precisely at the end of the coupling step in volumes as low as 0.25 mL. The pre-calibrated pump module does not require on-going calibration thereby avoiding drifting delivery amounts. Additionally, the main solvent and the activator (Oxyma Pure) are also delivered through similar individual pumps within the module for improved performance

¹ J. Collins, K. Porter, S. Singh and G. Vanier, “HighEfficiency Solid Phase Peptide Synthesis (HE-SPPS),” Org. Lett., vol. 16, pp. 940-943, 2014.
² Patent Pending: US20170226152; WO2017070512

High Efficiency Solid Phase Peptide Synthesis (HE-SPPS)
HE-SPPS is a significant advancement for solid phase peptide synthesis. It originates from our pioneering work in developing microwave assisted SPPS introduced at the 2003 American Peptide Symposium.¹ At this time, we introduced a new process for making peptides based on the use of microwave energy for both the deprotection and coupling steps in SPPS. This technology has demonstrated improvements for thousands of peptides with CEM’s peptide synthesis instrumentation. ² To support microwave SPPS, we have also utilized in-situ fiber optic temperature monitoring to provide true internal solution temperature control. This is essential for fast reaction heating with temperature control as it is well known that the outside of a reaction vessel can be at a significantly different temperature than the inside. ³ In 2013, we developed an improved methodology for microwave SPPS based on the use of higher temperature carbodiimide based coupling at 90°C along with the elimination of all washing after each coupling step. ⁴ These insights led to significant time and solvent saving while providing peptides of incredibly high purity. The more acidic coupling environment with carbodiimide chemistry overcomes coupling issues for cysteine (epimerization) and arginine (γ-lactam formation) which were previously an issue under more basic coupling conditions (ex. HCTU/DIEA). The instrumentation design used on CEM’s Liberty BlueTM peptide synthesizer is also a critical component of HE-SPPS to eliminate inefficient internal fluidic and reagent path cleaning that increases waste generated. HE-SPPS used on the Liberty Blue is now used in hundreds of laboratories worldwide and provides very fast, high purity peptides with incredibly low waste generated.

¹ Collins, J.M., Collins, M.J., and Steorts, R.C., “A Novel Method for Solid Phase Peptide Synthesis Using Microwave Energy” Biopolymers, 71, 361 2003.
² US7393920; US7582728; US8058393; JP4773695
³ M. Herrero, J. Kremsner and C.O. Kappe, “Nonthermal Microwave Effects Revisited: On the Importance of Internal Temperature Monitoring and Agitation in Microwave Chemistry,” J. Org. Chem., vol. 73, pp. 36-47, 2008.
⁴ J. Collins, K. Porter, S. Singh and G. Vanier, “High-Efficiency Solid Phase Peptide Synthesis (HE-SPPS),” Org. Lett., vol. 16, pp. 940-943, 2014.

Chemistry Technology
• HE-SPPS
• One-Pot Coupling/Deprotection
• CarboMAX

Enhanced Hardware
The Liberty PRIME™ features enhanced delivery options of the main solvent and Deprotection solutions compared to the Liberty Blue system. These reagents are delivered by a pre-calibrated pumping system, not requiring calibration or affected by restriction changes in the delivery path. This reduces system maintenance and provides an ideal system for GMP environments that is free of calibration.

Performance