title: Solid-phase route to Fmoc-protected cationic amino acid building blocks.
abstract: Diamino acids are commonly found in bioactive compounds, yet only few are commercially available as building blocks for solid-phase peptide synthesis. In the present work a convenient, inexpensive route to multiple-charged amino acid building blocks with varying degree of hydrophobicity was developed. A versatile solid-phase protocol leading to selectively protected amino alcohol intermediates was followed by oxidation to yield the desired di- or polycationic amino acid building blocks in gram-scale amounts. The synthetic sequence comprises loading of (S)-1-(p-nosyl)aziridine-2-methanol onto a freshly prepared trityl bromide resin, followed by ring opening with an appropriate primary amine, on-resin N(β)-Boc protection of the resulting secondary amine, exchange of the N(α)-protecting group, cleavage from the resin, and finally oxidation in solution to yield the target γ-aza substituted building blocks having an Fmoc/Boc protection scheme. This strategy facilitates incorporation of multiple positive charges into the building blocks provided that the corresponding partially protected di- or polyamines are available. An array of compounds covering a wide variety of γ-aza substituted analogs of simple neutral amino acids as well as analogs displaying high bulkiness or polycationic side chains was prepared. Two building blocks were incorporated into peptide sequences using microwave-assisted solid-phase peptide synthesis confirming their general utility.
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.
authors.forename: Jacob Dahlqvist
authors.initials: JD
authors.lastname: Clausen
authors.forename: Lars
authors.initials: L
authors.lastname: Linderoth
authors.forename: Hanne Mørck
authors.initials: HM
authors.lastname: Nielsen
authors.forename: Henrik
authors.initials: H
authors.lastname: Franzyk
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D000605:Amino Alcohols / Q000737:chemistry; D001388:Aziridines / Q000737:chemistry; D004337:Drug Carriers / Q000138:chemical synthesis*; D005449:Fluorenes / Q000737:chemistry*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008872:Microwaves; D015394:Molecular Structure; D009842:Oligopeptides / Q000138:chemical synthesis*; D010084:Oxidation-Reduction; D011073:Polyamines / Q000737:chemistry*; D000071228:Polyelectrolytes; D012117:Resins, Synthetic; D060327:Solid-Phase Synthesis Techniques / Q000379:methods*; D055672:Static Electricity; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D000605:Amino Alcohols; D001388:Aziridines; D004337:Drug Carriers; D005449:Fluorenes; D009842:Oligopeptides; D011073:Polyamines; D000071228:Polyelectrolytes; D012117:Resins, Synthetic; C016456:N(alpha)-fluorenylmethyloxycarbonylamino acids