Solid Phase Syntheses of Oligoureas

Abstract

Isocyanates 7 were formed from monoprotected diamines 3 or 6, which in turn can be easily prepared from commercially available N-BOC- or N-FMOC-protected amino acid derivatives. Isocyanates 7, formed in situ, could be coupled directly to a solid support functionalized with amine groups or to amino acids anchored on resins using CH2Cl2 as solvent and an 11 h coupling time at 25 °C. Such couplings afforded peptidomimetics with an N-phthaloyl group at the N-terminus. The optimal conditions identified for removal of the N-phthaloyl group were to use 60% hydrazine in DMF for 1−3 h. Several sequences of amino acids coupled to ureas (“peptidic ureas”) and of sequential urea units (“oligoureas”) were prepared via solid phase syntheses and isolated by HPLC. Partition coefficients were measured for two of these peptidomimetics, and their water solubilities were found to be similar to the corresponding peptides. A small library of 160 analogues of the YGGFL-amide sequence was prepared via Houghten's tea bag methodology. This library was tested for binding to the anti-β-endorphin monoclonal antibody. Overall, this paper describes methodology for solid phase syntheses of oligourea derivatives with side chains corresponding to some of the protein amino acids. The chemistry involved is ideal for high-throughput syntheses and screening operations. The products can be expected to have an interesting range of pharmacological properties and enhanced proteolytic stabilities relative to the corresponding peptides.

Assessing enzyme substrate specificity using combinatorial libraries and electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry

“…2 (a)). The use of 0.1 M NH 4 OAc as screening buffer caused an elevated level of noise and changed the intensities of some peaks slightly. Since the high resolution analysis by FTICR enables us to distinguish between peaks of the same nominal mass and different elemental composition, it would be possible to detect product peaks closely spaced to contaminant peaks, if they were present.…”

“…GST (0.8 mg, 84% Biuret, 83 units/mg protein, Sigma, St. Louis, MO, USA) from bovine liver was dissolved in NH 4 OAc buffer (200 mL, 0.1 M pH 6.5), placed in a MicroCon 10 (Amicon Inc., Beverly, MA, USA) and concentrated by centrifugation at 4 °C (12 000 rpm, 10-12 min). The protein was diluted 3 times in 100 mL buffer with subsequent concentration by centrifugation.…”

“…Cys-Xxx-OH library (1.8 mg) was redissolved in degassed NH 4 OAc buffer (200 mL, 0.1 M, pH 6.5). An aliquot of 1-chloro-2,4-dinitrobenzene solution (CDNB) 15 in ethanol (5 mL, 200 mM) was added, followed by a solution of freshly prepared enzyme (10 mL).…”

“…1 Emerging combinatorial technology offers a powerful way to address this challenge. Although peptide, 2 oligonucleotide 3 and various small molecule [4][5][6][7] libraries have been successfully used to explore receptor-ligand interactions, 8,9 very few studies have been performed where components of libraries are enzymatically transformed as part of the combinatorial experiment. 10 This situation challenges the field of analytical chemistry to develop instrumentation for the high throughput screening of complex libraries.…”

Solid‐Phase Synthesis of Cyclic C‐Glycoside/Amino Acid Hybrids by Carbamate Coupling Chemistry and On‐Support Cyclization

“…In addition, their hydrogen bonding properties and, hence, folding patterns differs from those of native peptides and oligosaccharides. Several oligourea- [20] and oligocarbamate-based [21] peptidomimics have been prepared by solid phase synthesis using isocyanates, [20a] p-nitrophenyl carbamates [20b-20e] and p-nitrophenyl carbonates [21] as activated monomeric building blocks. Carbohydrate mimics have, in turn, been obtained by coupling of azasugar building blocks activated in situ with bis(4-nitrophenyl) carbonate.…”