Synthesis of aminooxy and N-alkylaminooxy amines for use in bioconjugation.

Five Boc-protected aminooxy and N-alkylaminooxy amines have been synthesized in 60-95% overall yield using a common synthetic strategy from readily available two- and three-carbon Cbz-protected amino alcohols. The amines can be linked to biomolecules via amide formation and incorporated directly into peptoids via submonomer synthesis. Subsequent deprotection of the aminooxy and N-alkylaminooxy groups enables conjugation with desired target molecules via established chemoselective ligation methods.

Chemoselective and microwave-assisted synthesis of glycopeptoids.

The chemoselective glycosylation of N-alkylaminooxy side chains with unprotected reducing sugars has proven useful for the synthesis of glycopeptides. Herein, we extend the N-alkylaminooxy strategy to the synthesis of glycopeptoids. A N-methylaminooxy submonomer was efficiently synthesized and incorporated into peptoids.

Glucose-permeable interpenetrating polymer network hydrogels for corneal implant applications: a pilot study.

Epithelialization of a keratoprosthesis requires that the implant material be sufficiently permeable to glucose. We have developed a poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) interpenetrating polymer network (IPN) hydrogel that can provide adequate passage of glucose from the aqueous humor to the epithelium in vivo. A series of PEG/PAA IPNs with varying PEG macromonomer molecular weights were synthesized and evaluated through swelling studies to determine their water content and diffusion experiments to assess their permeability to glucose.

Design and fabrication of an artificial cornea based on a photolithographically patterned hydrogel construct.

We describe the design and fabrication of an artificial cornea based on a photolithographically patterned hydrogel construct, and demonstrate the adhesion of corneal epithelial and fibroblast cells to its central and peripheral components, respectively. The design consists of a central "core" optical component and a peripheral tissue-integrable "skirt." The core is composed of a poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) double-network with high strength, high water content, and collagen type I tethered to its surface.

Chemoselective alkylation of N-alkylaminooxy-containing peptides.

Peptides containing N-alkylaminooxy amino acids were chemoselectively alkylated with allylic, benzylic, and alpha-carbonyl bromides, N-ethylmaleimide, and hexyl acrylate in mildly acidic aqueous/organic solutions. Alkylation at the aminooxy nitrogen proceeds in good yields with excellent to complete chemoselectivity in the presence of all common amino acids except cysteine. This reaction complements the selective glycosylation and acylation of N-alkylaminooxy groups and provides an avenue for the synthesis of peptide arrays comprising a wide variety of neoglycopeptides and neolipopeptides.

2-(N-Fmoc)-3-(N-Boc-N-methoxy)-diaminopropanoic acid, an amino acid for the synthesis of mimics of O-linked glycopeptides.

Amino acids with N-alkylaminooxy side chains have proven effective for the rapid synthesis of neoglycopeptides. Chemoselective reaction of reducing sugars with peptides containing these amino acids provides glycoconjugates that are structurally similar to their natural counterparts. 2-(N-Fmoc)-3-(N-Boc-N-methoxy)-diaminopropanoic acid (Fmoc: 9-fluorenylmethoxycarbonyl; Boc: t-butyloxycarbonyl) was synthesized from Boc-Ser-OH in >40% overall yield and incorporated into peptides by standard Fmoc chemistry based solid phase peptide synthesis.

A versatile set of aminooxy amino acids for the synthesis of neoglycopeptides.

Four N-alkylaminooxy amino acids have been synthesized in 22-56% overall yield from readily available amino acid precursors. Each amino acid can be efficiently incorporated into peptides using Boc-chemistry-based solid-phase peptide synthesis, and in three of the four cases the resulting peptides can be chemoselectively glycosylated at the aminooxy side chains to generate neoglycopeptides. The range of N-alkylaminooxy amino acids prepared allows attachment of sugars at two-, three-, or four-atom distances from the peptide backbone, and each ensures that attached sugars adopt cyclic conformations.

Synthesis of N-Fmoc-O- (N'-Boc-N'-methyl)-aminohomoserine, an amino acid for the facile preparation of neoglycopeptides.

The synthesis of N-Fmoc-O-(N'-Boc-N'-methyl)-aminohomoserine in 35% overall yield from l-homoserine is described. This amino acid can be efficiently incorporated into peptides using Fmoc-chemistry-based solid-phase peptide synthesis, and the resulting peptides can be chemoselectively glycosylated at the aminooxy side chains to generate neoglycopeptides. The synthesis of this derivative greatly expands the availability of a previously developed neoglycopeptide synthesis strategy.

Dap-SL: a new site-directed nitroxide spin labeling approach for determining structure and motions in synthesized peptides and proteins.

A new approach for site-directed placement of nitroxide spin labels in chemically synthesized peptides and proteins is described. The scheme takes advantage of a novel diaminopropionic acid scaffold to independently control backbone and side chain elongation. The result is a spin-labeled side chain, referred to as Dap-SL, in which an amide bond forms a linker between the nitroxide and the peptide backbone.