Fmoc-Asp-OtBu

Fmoc-Asp-OtBu

New t-butyl based aspartate protecting groups preventing aspartimide formation in Fmoc SPPS.[Pubmed:26077723]

J Pept Sci. 2015 Aug;21(8):680-7.

Obtaining homogenous aspartyl-containing peptides via Fmoc/tBu chemistry is often an insurmountable obstacle. A generic solution for this issue utilising an optimised side-chain protection strategy that minimises aspartimide formation would therefore be most desirable. To this end, we developed the following new derivatives: Fmoc-Asp(OEpe)-OH (Epe = 3-ethyl-3-pentyl), Fmoc-Asp(OPhp)-OH (Php = 4-n-propyl-4-heptyl) and Fmoc-Asp(OBno)-OH (Bno = 5-n-butyl-5-nonyl). We have compared their effectiveness against that of Fmoc-Asp(OtBu)-OH and Fmoc-Asp(OMpe)-OH in the well-established scorpion toxin II model peptide variants H-Val-Lys-Asp-Asn/Arg-Tyr-Ile-OH by treatments of the peptidyl resins with the Fmoc removal reagents containing piperidine and DBU at both room and elevated temperatures. The new derivatives proved to be extremely effective in minimising aspartimide by-products in each application.

Parallel high-throughput accurate mass measurement using a nine-channel multiplexed electrospray liquid chromatography ultraviolet time-of-flight mass spectrometry system.[Pubmed:12820207]

Rapid Commun Mass Spectrom. 2003;17(13):1425-32.

A nine-channel multiplexed electrospray (MUX) liquid chromatography ultraviolet time-of-flight mass spectrometry (LC/UV/TOFMS) system has been used to simultaneously measure accurate masses of eluting components from eight parallel gradient LC columns. Accuracies better than 5 and 10 ppm were achieved for 50 and 80% of samples, respectively, from a single batch analysis of ten plates (960 samples) of a Fmoc-Asp(OtBu)-OH and reserpine mixture. Combinatorial library compounds were analyzed using this parallel high-throughput system in both positive and negative modes to rigorously verify expected products and identify side products. A mass accuracy of 10 ppm root mean square (RMS) is routinely obtained for combinatorial library samples from this high-throughput accurate mass LC/MS system followed by automated data processing. This mass accuracy is critical in revealing combinatorial synthesis problems that would be missed by unit mass measurement.

Synthesis of prothymosin alpha deduced from nucleotide sequence of the murine cDNA and its effect on the impaired T lymphocytes of uremic patients.[Pubmed:8292970]

Biotechnol Ther. 1993;4(3-4):213-20.

The complete murine prothymosin alpha molecule (110 residues) except for the N-terminal methionine deduced from the cloned cDNA has been synthesized by a solid-phase method. Peptide synthesis was performed manually by the stepwise solid-phase method using the base-labile Fmoc group for protecting the alpha-amino group. The peptide was assembled on a p-alkoxybenzyl alcohol resin. After the last coupling step, the Fmoc group was removed with 50% piperidine in DMF. The peptide resin was treated with thioanisole-o-cresol in TFA, and then purified by gel filtration, ion-exchange column chromatography and high-performance liquid chromatography. A 2.9-mg sample of a highly purified peptide was finally obtained. The overall yield of the synthesis was less than 1%, based on the amino acid content of the starting Fmoc-Asp (OtBu)-resin. The synthetic peptide was found to have a restoring activity on low-E-rosette-forming lymphocytes after incubation of peripheral blood from uremic patients with the synthetic peptide. This peptide exhibited far stronger restoring effect than that of our synthetic thymosin alpha 1.

A 'conovenomic' analysis of the milked venom from the mollusk-hunting cone snail Conus textile--the pharmacological importance of post-translational modifications.[Pubmed:24055806]

Peptides. 2013 Nov;49:145-58.

Cone snail venoms provide a largely untapped source of novel peptide drug leads. To enhance the discovery phase, a detailed comparative proteomic analysis was undertaken on milked venom from the mollusk-hunting cone snail, Conus textile, from three different geographic locations (Hawai'i, American Samoa and Australia's Great Barrier Reef). A novel milked venom conopeptide rich in post-translational modifications was discovered, characterized and named alpha-conotoxin TxIC. We assign this conopeptide to the 4/7 alpha-conotoxin family based on the peptide's sequence homology and cDNA pre-propeptide alignment. Pharmacologically, alpha-conotoxin TxIC demonstrates minimal activity on human acetylcholine receptor models (100 muM, <5% inhibition), compared to its high paralytic potency in invertebrates, PD50 = 34.2 nMol kg(-1). The non-post-translationally modified form, [Pro](2,8)[Glu](16)alpha-conotoxin TxIC, demonstrates differential selectivity for the alpha3beta2 isoform of the nicotinic acetylcholine receptor with maximal inhibition of 96% and an observed IC50 of 5.4 +/- 0.5 muM. Interestingly its comparative PD50 (3.6 muMol kg(-1)) in invertebrates was ~100 fold more than that of the native peptide. Differentiating alpha-conotoxin TxIC from other alpha-conotoxins is the high degree of post-translational modification (44% of residues). This includes the incorporation of gamma-carboxyglutamic acid, two moieties of 4-trans hydroxyproline, two disulfide bond linkages, and C-terminal amidation. These findings expand upon the known chemical diversity of alpha-conotoxins and illustrate a potential driver of toxin phyla-selectivity within Conus.

On the use of N-dicyclopropylmethyl aspartyl-glycine synthone for backbone amide protection.[Pubmed:19924731]

J Pept Sci. 2010 Jan;16(1):65-70.

To prevent aspartimide formation and related side products in Asp-Xaa, particularly Asp-Gly-containing peptides, usually the 2-hydroxy-4-methoxybenzyl (Hmb) backbone amide protection is applied for peptide synthesis according to the Fmoc-protocols. In the present study, the usefulness of the recently proposed acid-labile dicyclopropylmethyl (Dcpm) protectant was analyzed. Despite the significant steric hindrance of this bulky group, N-terminal H-(Dcpm)Gly-peptides are quantitatively acylated by potent acylating agents, and alternatively the dipeptide Fmoc-Asp(OtBu)-(Dcpm)Gly-OH derivative can be used as a building block. In contrast to the Hmb group, Dcpm is inert toward acylations, but is readily removed in the acid deprotection and resin-cleavage step.