Fmoc- ß-HoAsp(OtBu)-OH

Fmoc- ß-HoAsp(OtBu)-OH

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.

Innovative chemical synthesis and conformational hints on the lipopeptide liraglutide.[Pubmed:27238390]

J Pept Sci. 2016 Jul;22(7):471-9.

Liraglutide is a new generation lipopeptide drug used for the treatment of type II diabetes. In this work, we describe new approaches for its preparation fully by chemical methods. The key step of these strategies is the synthesis in solution of the Lys/gamma-Glu building block, Fmoc-Lys-(Pal-gamma-Glu-OtBu)-OH, in which Lys and Glu residues are linked through their side chains and gamma-Glu is N(alpha) -palmitoylated. This dipeptide derivative is then inserted into the peptide sequence on solid phase. As liraglutide is obtained with great purity and high yield, our approach can be particularly attractive for an industrial production. We also report here the results of a circular dichroism conformational analysis in a membrane mimetic environment that offers new insights into the mechanism of action of liraglutide. Copyright (c) 2016 European Peptide Society and John Wiley & Sons, Ltd.

Synthesis of complex head-to-side-chain cyclodepsipeptides.[Pubmed:27658010]

Nat Protoc. 2016 Oct;11(10):1924-1947.

Cyclodepsipeptides are cyclic peptides in which at least one amide link on the backbone is replaced with an ester link. These natural products present a high structural diversity that corresponds to a broad range of biological activities. Therefore, they are very promising pharmaceutical candidates. Most of the cyclodepsipeptides have been isolated from marine organisms, but they can also originate from terrestrial sources. Within the family of cyclodepsipeptides, 'head-to-side-chain' cyclodepsipeptides have, in addition to the macrocyclic core closed by the ester bond, an arm terminated with a polyketide moiety or a branched amino acid, which makes their synthesis a challenge. This protocol provides guidelines for the synthesis of 'head-to-side-chain cyclodepsipeptides' and includes-as an example-a detailed procedure for preparing pipecolidepsin A. Pipecolidepsin was chosen because it is a very complex 'head-to-side-chain cyclodepsipeptide' of marine origin that shows cytotoxicity in several human cancer cell lines. The procedure begins with the synthesis of the noncommercial protected amino acids (2R,3R,4R)-2-{[(9H-fluoren-9-yl)methoxy]carbonylamino}-3-hydroxy-4,5-dimethylhexa noic acid (Fmoc-AHDMHA-OH), Alloc-pipecolic-OH, (4R,5R)-5-((((9H-fluoren-9-yl)methoxy)carbonylamino)-4-oxo-4-(tritylamino)butyl)- 2,2-dimethyl-1,3-dioxolane-4-carboxylic acid (Fmoc-DADHOHA(acetonide, Trt))-OH and the pseudodipeptide (2R,3R,4R)-3-hydroxy-2,4,6-trimethylheptanoic acid ((HTMHA)-D-Asp(OtBu)-OH). It details the assembly of the depsipeptidic skeleton using a fully solid-phase approach (typically on an amino polystyrene resin coupled to 3-(4-hydroxymethylphenoxy)propionic acid (AB linker)), including the key ester formation step. It concludes by describing the macrocyclization step performed on solid phase, and the global deprotection and cleavage of the cyclodepsipeptide from the resin using a trifluoroacetic acid-H2O-triisopropylsilane (TFA-H2O-TIS; 95:2.5:2.5) cocktail, as well as the final purification by semipreparative HPLC. The entire procedure takes approximately 2 months to complete.

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.

A paclitaxel-conjugated adenovirus vector for targeted drug delivery for tumor therapy.[Pubmed:21959006]

Biomaterials. 2012 Jan;33(1):146-62.

Tumor-targeted drug delivery is an attractive strategy in cancer treatment. Our previous study demonstrated that modified adenovirus has strong tumor targeting ability and less toxicity to surrounding normal tissue. In this study, Paclitaxel (PTX), a widely used clinical anticancer drug, was conjugated to folate-modified adenovirus (Ad) nanoparticles by using succinic anhydride and Fmoc-Glu(OtBu)-OH linkers to form two prodrugs, FA-Ad-Suc-PTX and FA-Ad-ICG02-Glu-PTX. Near-infrared (NIR) fluorescent dye ICG-Der-02 was attached to -NH(2)-Glu(OtBu)-PTX for in vivo optical imaging. In vitro and acute toxicity study demonstrates the low toxicity of the prodrug FA-Ad-Suc-PTX and FA-Ad-ICG02-Glu-PTX compared to the free drug. The dynamic behaviors and targeting ability of FA-Ad-ICG02-Glu-PTX on MDA-MB-231 tumor-bearing mice were investigated by NIR fluorescence imaging. The result show that PTX-conjugated Ad vector could enhance the targeting and residence time in tumor site. In vitro and in vivo studies demonstrate that Coxsackie adenovirus receptor (CAR) or foliate receptor (FR)-mediated uptake of FA-Ad-loaded PTX induced highly anti-tumor activity. The results support the potential of using chemically modified Ad vector as drug-loaded tumor-targeting delivery system.