An improved synthesis of arsenic-biotin conjugates

An amide linked conjugate of p-aminophenylarsine oxide and biotin is conveniently prepared in a one-pot procedure by the reaction of biotinyl chloride, formed in situ, with p-aminophenyldichloroarsine. The reaction of the arsine oxide-biotin conjugate with 1,2-ethanedithiol produces the stabilized dithiarsolane. These reagents are now readily available for a variety of applications.     

Chemical synthesis of bilirubin glucuronide conjugates

In dimethylformamide, the two carboxyl groups of bilirubin react with the bifunctional coupling agent, carbonyldiimidazole, to form bilirubin diimidazole, which was isolated and crystallised. The bilirubin diimidazole, termed “activated bilirubin”, was shown to react spontaneously with primary alcohols to form diesters of bilirubin. After addition of the tetrabutyl ammonium salt of glucuronic acid, compounds with chromatographic mobilities similar to those of bilirubin mono- and diglucuronides from bile were formed.Bilirubin diglucuronides were isolated by barium precipitation followed by solvent extraction. The bilirubin diglucuronides were considered to be a mixture of α and β glucuronides esterified at positions 1, 2, 3, or 4 of glucuronic acid because the compound(s) was resistant to hydrolysis with glucuronidase and gave multiple spots by chromatography after diazotization with ethyl anthranilate. The model compounds lauryl glucuronides were synthesized similarly; the most polar product by chromatography had identical chromatographic mobility to synthetic lauryl l-d-glucuronide prepared by reductive debenzylation of lauryl (benzyl (2,3,4-tri-O-benzyl))-d-glucuronide.It is concluded that bilirubin-1-di-β-d-glucuronide can be synthesized when suitable protecting groups for the 2, 3, and 4 hydroxyl groups of glucuronic acid become available.     

Enzymatic synthesis of disaccharide-serine and peptide conjugates

We describe enzymatic transglycosylations between an appropriate glycosyl donor and galactosyl (or glucosyl)-serine and -peptide conjugates to obtain diglycosyl-serine or -peptide derivatives. The reactions are catalyzed by β-galactosidase (from E. coli or from Aspergillus oryzae) and β-glucosidase (from Almonds). The enzymatic reactions give, preferentially, β(1 å6) linked diglycosyl-serine (or -peptide) conjugates. However, in the case of the digalactosyl derivatives, β(1 å3) linkages are mainly observed. By changing the source of the enzyme (E. coli or Aspergillus oryzae) the regioselectivity can be reversed for these digalactosyl derivatives. Deprotection of the aminoacid of the diglycosyl-peptides under mild conditions is also described.     

Chemical synthesis of Haemophilus influenzae glycopeptide conjugates

A simple procedure for conjugating synthetic fragments of the capsular polysaccharide of Haemophilus influenzae type b, poly-3--D-ribose-(1, 1)-D-ribitol-5-phosphate (sPRP) to linear peptides is described. The procedure consists of (i) reacting the amino group of amino-heptyl sPRP with m-maleimidobenzoyl-N-hydroxysuccinimide (MBS) in phosphate buffer, pH 7.5; (ii) selectively coupling the MBS-modified sPRP to the sulfhydryl group of the cysteine residue of peptides containing functional T-helper cell epitope(s). The glycopeptide conjugates were purified by gel filtration chromatography, biochemically characterized, and elicited protective level of anti-PRP antibody responses in rabbits. Abbreviations: PRP, poly-3--D-ribose-(1, 1)-D-ribitol-5-phosphate; sPRP, synthetic oligo-3--D-ribose-(1, 1)-D-ribitol-5-phosphate; Hib, Haemophilus influenzae type b; MBS, m-maleimidobenzoyl-N-hydroxysuccinimide; PEG, polyethylene glycol monomethyl ether; CRM 197, a non-toxic diphtheria toxin mutant; TT, tetanus toxoid; DT, diphtheria toxoid; OMP, outer membrane protein; RP-HPLC reverse phase high pressure liquid chromatograph     

Versatile methods for the synthesis of mixed-acid 1,2-diacylglycerols

Two methods for synthesizing mixed-acid 1,2-diacylglycerols starting from 2,3-epoxy-1-propanol (glycidol) or 3-chloro-1,2-propanediol have been described. This first method involves fatty acid addition to a protected glycidol derivative and solid-state isomerization. The second approach exploits the specificity of the trityl group for primary alcohols and the nucleophilic replacement of chlorine by a carboxylate ion in an aprotic solvent. The second method proves to be more general: with 3-chloro-1-O-trityl-1,2-propanediol as an intermediate compound apparently all types of mixed-acid, saturated and unsaturated, chiral and racemic 1,2-diacylglycerols can be prepared in good yields. In the first method tritylglycidol is a good starting compound. The use of this method, however, is restricted because only the 2-position of glycerol can be occupied with an unsaturated fatty acid. For de-blocking protected 1,2-diacylglycerols, the trityl group and other protecting groups were exchanged for the trifluoroacetyl group, which group could then be removed without any detectable acyl migration (< 1%). To this end, the 1,2-diacyl-3-trifluoroacetyl-glycerols were dissolved at room temperature in methanol containing pyridine, whereby the trifluoroacetyl group was split off, giving the 1,2-diacylglycerol.     

The synthesis of TNF-alpha conjugates with alendronic acid

Conjugates of recombinant human tumor necrosis factor alpha (TNFα) and alendronic acid linked through the protein sulfhydryl, carboxyl, and amino groups were obtained with crosslinking agents of different types. The conjugation reactions were conducted in solution and on a solid phase. Unlike the conjugation reactions in solution, the method involving immobilization of active components on a hydroxyapatite column was shown to result in the conjugates with a specified stoichiometry and a high degree of homogeneity. The TNFα conjugates retained the specific cytolytic activity and demonstrated the higher affinity to hydroxyapatite, an analogue of the bone mineral matrix, than TNFα.     

The synthesis and chelation chemistry of DOTA-peptide conjugates

Metal complexes of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid)-peptide conjugates are increasingly used as targeted imaging and therapeutic radiopharmaceuticals and MRI contrast agents. This review covers the bifunctional derivatives of DOTA, the solution and solid-phase synthesis of DOTA-peptide conjugates, their coordination and chelation chemistry, and the biomedical applications of various DOTA-peptide conjugate metal complexes.     

Enzymatic synthesis and antioxidant property of gelatin-catechin conjugates

Gelatin-catechin conjugate was synthesized by the laccase-catalyzed oxidation of catechin in the presence of gelatin. The conjugate had a good scavenging activity against superoxide anion radicals. Moreover, the conjugate showed an amplified inhibition effect on human low density lipoprotein oxidation initiated by 2,2'-azobis(2-amidinopropane)dihydrochloride as a radical generator.     

Evaluating coupling procedures for synthesis of lna-Peptide conjugates

As initial studies of block coupling of peptides with C-terminal glycines, we have evaluated of coupling of glycine building blocks under various conditions to a preassembled solid support bound LNA-fragment. Potentially competing side reaction have been studied and we have worked out a procedure for trifluoroacetyl protection of peptides.     

Design and synthesis of novel antibacterial peptide-resin conjugates

We synthesized a novel peptide-resin conjugate by immobilizing beta-sheet antibacterial peptide on PEG-PS resin. The peptide-resin conjugate, similar to cationic antimicrobial peptides, demonstrated unique properties such as potent antibacterial activity, no hemolytic activity, lipid membrane perturbation activity, and potent synergism with vancomycin. Specially, the peptide-resin conjugate showed a more increased lipid membrane perturbation activity in comparison to unbound beta-sheet antibacterial peptide.     

Efficient synthesis of oligonucleotide-peptide conjugates on large scale

The conjugation of oligonucleotide phosphorothioates with antennapedia peptide was studied in detail to allow efficient preparation of the conjugates on up to 15 mumol scale. Under optimized conditions, the use of oligonucleotides and the peptide in an equimolecular ratio gave the desired conjugates in more than 60% isolated yield.     

Design, synthesis and DNA-cleavage of Gly-Gly-His-naphthalene diimide conjugates

Naphthalene diimides with one and two metal-chelating Gly-Gly-His (GGH) motifs have been synthesized. Both conjugates induce single-stranded cleavage of plasmid pBR322 DNA in the presence of nickel and Oxone and are approximately 100-fold more efficient than Ni(II) x GH-CONH2 itself.     

The first synthesis of chiral PNA monomer-cyclen conjugates.

A synthetic route to novel chiral PNA monomer-cyclen conjugates was described for the first time, the targeted products were obtained in high yields under mild reaction conditions. The preliminary results demonstrated that the uracil-PNA monomer-cyclen conjugates can rapidly bind Zn2+ in aqueous solution, and the structure of the Zn(II) complex was confirmed facilely by HRMS spectra, 1H NMR spectra and elemental analysis.     

Rapid synthesis of DNA-cysteine conjugates for expressed protein ligation

We report a rapid method for the covalent modification of commercially available amino-modified DNA oligonucleotides with a cysteine moiety. The resulting DNA-cysteine conjugates are versatile reagents for the efficient preparation of covalent DNA-protein conjugates by means of expressed protein ligation (EPL). The EPL method allows for the site-specific coupling of cysteine-modified DNA oligomers with recombinant intein-fusion proteins, the latter of which contain a C-terminal thioester enabling the mild and highly specific reaction with N-terminal cysteine compounds. We prepared a cysteine-modifier reagent in a single-step reaction which allows for the rapid and near quantitative synthesis of cysteine-DNA conjugates. The latter were ligated with the green fluorescent protein mutant EYFP, recombinantly expressed as an intein-fusion protein, allowing for the mild and selective formation of EYFP-DNA conjugates in high yields of about 60%. We anticipate many applications of our approach, ranging from protein microarrays to the arising field of nanobiotechnology.     

Efficient synthesis of rhodamine conjugates through the 2'-position

Reaction of substrates containing primary amines with rhodamine 2'-esters cleanly produces fluorescent rhodamine 2'-amide conjugates at ambient temperature. Only primary amines react with the esters under these conditions. Chemoselectivity can thus be achieved in substrates containing different types of amines.     

Versatile solid supports for oligonucleotide synthesis that incorporate urea bridge

The universal solid support, USIII, representing a new and improved version of commercial USII, as well as 2 '-deoxynucleoside and 2 '-deoxy-2 '-fluoronucleoside bound supports, incorporating a labile phenoxyacetyl fragment, was synthesized by an aminomethyl polystyrene carbamoylation with corresponding azides in the presence of aqueous triethylammonium bicarbonate. All three solid phases incorporate a stable urea tether, thus bridging the polymer and functional linker. These new matrices proved to be potent solid phases for the synthesis of DNA, RNA, or modified oligonucleotides as well as randomized mixed 2 '-ribo/2 '-deoxy-2 '-fluoro-RNA libraries and/or DNA libraries, randomized with trinucleotides (codons).