Bachem - insights into peptide chemistry achievements by the world's leading independent manufacturer of peptides.

The Swiss fine chemicals company Bachem, pioneer and specialist in the chemical synthesis of peptides, has also become an internationally leading manufacturer of peptide active pharmaceutical ingredients (APIs). In response to increasing demands in scale and purity, Bachem's research efforts centered on the chemistry involved in solid-phase peptide synthesis and the production of the required amino acid derivatives with the aim of a continuous improvement of the technology. The resulting optimized protocols together with high-throughput equipment enabled us to manufacture long peptide APIs and, more recently, even pharma-grade glycoproteins in industrial scale.

Quantitative assessment of preloaded 4-alkoxybenzyl alcohol resins for solid-phase peptide syntheses by 1D and 2D HR-MAS NMR.

The quality of preloaded Wang resins is very important for the success of solid-phase peptide syntheses (SPPS). A critical factor is the capping of remaining hydroxyl groups after loading with the first amino acid, since these free alcohols lead to truncated sequences during the following SPPS steps. Because the detection of hydroxyl groups by color tests is difficult and unreliable, the capping efficiency is often controlled by time-consuming peptide test syntheses. Here, we describe a two-dimensional, high resolution magic angle spinning NMR method for the quantitative determination of remaining 4-alkoxybenzyl alcohols in Fmoc-Xaa-Wang resins with a detection limit of 1 mol-%. The NMR method was validated with samples of known ratios between Fmoc-Ala-Wang and 4-alkoxybenzylalcohol resin. Application to a set of preloaded Fmoc-Ala- and Fmoc-Thr(tBu)-Wang test resins demonstrated that the full range of essential amino acids can be quantified without further spectrometer calibration. Compared to established test synthesis protocols, the NMR method represents not only advantages in terms of time and cost savings but also eliminates all inaccuracies due to further sample treatment like SPPS and cleavage from the resin.

Formation of Fmoc-beta-alanine during Fmoc-protections with Fmoc-OSu.

During the Fmoc-protection of H-alpha-Me-Val-OH, an unknown side product was found and isolated. The characterization using various analytical methods led unambiguously to the result that Fmoc-beta-Ala-OH was formed during the reaction. The reagent Fmoc-OSu was proven to be the source of Fmoc-beta-Ala-OH, following a mechanism that involved many deprotonation and elimination steps and a Lossen-type rearrangement as key sequence. The impurity Fmoc-beta-Ala-OH was found in a variety of reactions in which Fmoc-OSu was applied, either in the reaction mixture or as a contamination of the crude product. Purification of the Fmoc-amino acid derivatives from this impurity incurred high costs and significant reductions in yield.

Synthesis and application of an auxiliary group for chemical ligation at the X-gly site.

An efficient synthesis of an auxiliary group, the 2-mercapto-4,5-dimethoxybenzyl (Dmmb) moiety, to form a Gly-building block is presented. The building block was incorporated into peptides to study the reaction with thiobenzyl-activated derivatives. The target peptides have been obtained by standard chemical ligation reaction, followed by TMSBr-assisted cleavage to remove the auxiliary group. Prior to Dmmb removal, under acidic conditions an unexpected rearrangement was observed and evidence for a mechanism is provided.