Support For Solid-phase Synthesis Research Articles

End-Modifications on Morpholino Oligos.

Modifications at either end, both ends, or in-between the ends of a Morpholino oligo provide functional groups for further conjugation. Amino groups are the most useful and efficient reactive entities for chemical bonding with other molecules. The combination of modifications at both ends, especially with double functionalization at the 3'-end, yields myriad opportunities for diverse applications. An orthogonally protected diamine for advanced 3'-end double modification on the solid phase synthesis support allows the convenient assembly of a vast variety of custom-designed molecules. A particular application is the assembly of a class of Vis-Vivo-Morpholino where at the 3'-end an optically visible fluorophore is installed at one side for fluorescent detection and an in vivo delivery moiety is attached at the other side for intracellular activity studies.

Role of aliphatic hydrocarbon content in non-solvating porogens toward porosity of cross-linked microbeads

Megaporous spherical acrylate copolymer beads were synthesized by suspension polymerization using non-solvating porogens. Non-solvating porogens with higher aliphatic hydrocarbon content generated megaporous morphology with lower surface area. Surface area increased and inversely megaporosity was decreased with decrease in the aliphatic hydrocarbon content of porogen. Megaporosity (5.47 μm) and pore volume of 5.52 cm3/g was obtained with n-decanol. Thermal property of copolymer is a function of type (rigidity/flexibility/elemental composition) and concentration (cross-link density) of monomer and cross-linker. Copolymer containing rigid cross-linker (divinylbenzene) had better thermal stability over copolymer with flexible cross-linker (ethylene dimethacrylate). Further, higher concentration of rigid cross-linker or lower concentration of flexible cross-linker enhanced the thermal stability. Porous polymers are potentially recognized as a solid support for solid-phase synthesis.

Porous silicon-based nanostructured microparticles as degradable supports for solid-phase synthesis and release of oligonucleotides

We describe the preparation of several types of porous silicon (pSi) microparticles as supports for the solid-phase synthesis of oligonucleotides. The first of these supports facilitates oligonucleotide release from the nanostructured support during the oligonucleotide deprotection step, while the second type of support is able to withstand the cleavage and deprotection of the oligonucleotides post synthesis and subsequently dissolve at physiological conditions (pH = 7.4, 37°C), slowly releasing the oligonucleotides. Our approach involves the fabrication of pSi microparticles and their functionalisation via hydrosilylation reactions to generate a dimethoxytrityl-protected alcohol on the pSi surface as an initiation point for the synthesis of short oligonucleotides.

Release of DNA Oligonucleotides and Their Conjugates from Controlled‐Pore Glass Under Thermolytic Conditions

The sequential functionalization of long-chain alkylamine controlled-pore glass (CPG) with a 3-hydroxypropyl-(2-cyanoethyl)thiophosphoryl linker and a dinucleoside phosphorotetrazolide leads to a uniquely engineered support for solid-phase synthesis. Unlike conventional succinylated-CPG supports, this support is designed to allow oligonucleotide deprotection and elimination of deprotection side-products to proceed without release of the oligonucleotide. When needed, the DNA oligonucleotide can be thermolytically released in 2 hr under essentially neutral conditions. The modified CPG support has been successfully employed in the synthesis of both native and fully phosphorothioated DNA 20-mers. On the basis of reversed-phase HPLC and electrophoretic analyses, the purity of the released oligonucleotides is comparable to that of identical oligonucleotides synthesized from succinylated-CPG supports, in terms of both shorter-than-full-length oligonucleotide contaminants and overall yields. The detailed preparation of DNA oligonucleotides conjugated with exemplary reporter or functional groups, either at the 3'-terminus or at both 3'- and 5'-termini, is also described.

Magnetic CLEAR Supports for Solid-Phase Synthesis of Peptides and Small Organic Molecules

Paramagnetic versions of the CLEAR supports were prepared by entrapment of magnetite particles during suspension polymerization of allylamine, trimethylolpropane ethoxylate (14/3 EO/OH) triacrylate, and trimethylolpropane trimethacrylate. Swelling studies in a broad range of solvents showed comparable swelling of magnetic beads and regular CLEAR beads. The application of the magnetic beads as the support in solid-phase synthesis of peptides (Leu-enkephalinamide, substance P, acyl carrier protein (65–74) amide, and amyloid β-protein (34–42) amide) and small organic affinity ligands based on the s-triazine scaffold was demonstrated. Adequate stability of the beads and retention of their magnetic properties were observed throughout the synthesis steps.

Contents: Macromol. Symp. 245‐246/2006

Paramagnetic versions of the CLEAR supports were prepared by direct incorporation of magnetite particles during suspension polymerization of allylamine, trimethylolpropane ethoxylate (14/3 EO/OH) triacrylate, and trimethylolpropane trimethacrylate. Swelling studies in a broad range of solvents showed comparable swelling of composite beads and regular CLEAR beads. The application of the composite beads as the support in solid-phase synthesis of peptides and small organic affinity ligands is described. Adequate stability of the beads and retention of their magnetic properties were observed throughout the synthesis steps.

Heterogeneous Diazo-Transfer Reaction: A Facile Unmasking of Azide Groups on Amine-Functionalized Insoluble Supports for Solid-Phase Synthesis

Solid-supported azides are commonly generated through direct nucleophilic displacement of appropriately activated supports by the azide ion. This reaction usually proceeds rather sluggishly under harsh conditions. Here, we report that triflyl azide rapidly reacts with a series of amine-functionalized solid supports to generate azide-coated supports under mild conditions. Further, we demonstrate that the "azide coat" allows facile loading of alkyne-functionalized leader nucleoside monomers by click chemistry. Finally, we show that the nucleoside-functionalized supports are suitable for solid-phase oligonucleotide synthetic applications. The approach herein described extends the scope of the amine-azide conversion reaction and may be adaptable for the introduction of azide to diverse amine-terminated solid supports that are not easily accessible by the conventional nucleophilic displacement method.

A Convenient Orthogonally Cleavable Methionine Handle for Anchoring Amines to Polymeric Supports

Methionine has been used to anchor amines to polymeric supports for solid-phase synthesis. Either a "preformed handle" or a stepwise elongation strategy was followed. Cyanogen bromide (CNBr) treatment then released amines into solution. CNBr reaction variables were evaluated in order to converge to optimal cleavage conditions, and the strategy was shown to be effective for a range of primary and secondary amines, but not for aromatic amines.

A general approach to the quantification of resin-bound functional groups by NMR

There has been a continuing need for sensitive, accurate and rapid methods to monitor functional loading of insoluble supports for solid phase synthesis. The present articles reports our findings regarding functional group loading quantification using 1H NMR. Results obtained for supported amino, hydroxyl and NH-Fmoc groups are in agreement with those calculated using well-established methods and demonstrate that the strategy of looking, either at the excess reagent left in solution (NH2 and OH), or at the protecting group derivatives released from the polymer (Fmoc), is a viable approach to resin loading quantification.

Synthesis of Poly(aryl benzyl ether) Dendrimers on Solid Support

Dendronized supports, combining core Wang resin and poly(aryl benzyl ether) dendrons, were prepared using a novel route. Employing a dimethyl 5-hydroxyisophthalate module and a Mitsunobu condensation/ester reduction iterative sequence, the dendrimer was cleanly and efficiently prepared to the third generation. The synthesis was monitored using gel-phase 13C NMR and acidolytic cleavage, followed by 1H NMR. Gel-phase NMR and swelling experiments demonstrated that the behavior of the dendronized resins in various solvents is strongly influenced by the peripheral functional groups. Synthesis of a cinnamate derivative (via Mitsunobu and Heck reactions) and of a tripeptide demonstrated suitability of the dendronized support for solid-phase synthesis.

Hydrophilic polymer supports for solid-phase synthesis: preparation of poly(ethylene glycol) methacrylate polymer beads using "classical" suspension polymerization in aqueous medium and their application in the solid-phase synthesis of hydantoins.

Lightly cross-linked hydrophilic polymer beads representing new types of supports for solid-phase synthesis have been prepared from commercial oligoethylene glycol monomethacrylates using an aqueous suspension polymerization process and specifically designed polymerization mixtures. These beads swell extensively in solvents with a wide range of polarities from dichloromethane, tetrahydrofuran, and water to dimethylformamide, and they enable high functional loadings of 1.2-1.8 mmol g(-1). Their ability to serve as supports was demonstrated in the model solid-phase synthesis of a small library of hydantoins. This four-step synthesis using primary amines readily affords yields of over 70%.

Template-free segmental synthesis of oligonucleotides containing nonnative linkages.

Protected oligonucleotides containing 3'-alkyl carboxylic acids or 3'-alkylamines were obtained from photolabile solid-phase synthesis supports (1 and 4). Protected oligonucleotides containing 5'-alkylamines and 3'-hydroxyl groups were obtained using a photolabile solid-phase synthesis support (2) and a commercially available phosphoramidite reagent (3). Depending upon the source of alkylamine-containing oligonucleotide, the segments were coupled under mild conditions to form products containing either 5'-3' or 3'-3' linkages in good yield and high purity. Oligonucleotides as long as 40 nucleotides were prepared, and coupling yields of protected biopolymer segments were independent of length over the range examined. This method is particularly well suited for the convergent synthesis of oligonucleotides containing nonnative linkages and should be useful for the rapid assembly of modified biopolymers that are useful in biochemical studies.

New polyoxyalkyleneamine-grafted paramagnetic supports for solid-phase synthesis and bioapplications

The synthesis of some novel polyoxyalkyleneamine grafted paramagnetic supports for use in chemical and biological applications is described. These composite supports were synthesized by utilizing power ultrasound to enhance the level of incorporation of certain high molecular weight, polyoxyalkyleneamine (Jeffamine®) polymers into the matrix of a chloromethylated paramagnetic support. These new composite paramagnetic supports show excellent expansion properties in both organic solvents and water. The use of these grafted supports for multi-step solid-phase synthesis was then demonstrated by example.

Synthesis of 2'-modified oligodeoxynucleotides via on-column conjugation.

Oligodeoxynucleotides modified at the 2'-position of 2'-amino-2'-deoxyuridine or uridine were prepared in high yield and purity using phosphoramidites 2 and 3, respectively. Oligodeoxynucleotide conjugates were prepared on the solid-phase synthesis support following selective unmasking of the nucleophile incorporated in these phosphoramidites. Synthesis of oligodeoxynucleotides modified at the 2'-position of an internal nucleotide provides molecules that are complementary to those previously prepared via a similar approach using C5-substituted pyrimidines. The efficiency of functionalization of the 2'-O-alkylamino-uridine derived from 3 in a protected oligodeoxynucleotide was less susceptible to steric hindrance than the 2'-amino-2'-deoxyuridine in the same polymeric substrate. However, the greater reactivity of the 2'-O-alkylamine containing nucleotide gave rise to undesired acetamide formation resulting from nucleophilic attack on the 5'-terminal acetate in capped failure sequences. This problem was overcome by using 2,2,2-trimethylacetyl anhydride as a capping agent during the automated synthesis cycles. Finally, the efficiency of the photochemical unmasking of the support bound alkylamine on a 1 mumole scale was improved by using two 20 min photolysis cycles, coupled with removing reaction byproducts between cycles.

Trityl isothiocyanate support for solid-phase synthesis.

Trityl isothiocyanate resin [1], prepared from commercially available trityl chloride resin, is a useful precursor of the trityl thiosemicarbazide resin [2]. This resin can be employed in the solid-phase synthesis of a variety of supported isatin beta-thiosemicarbazones [4] and their Mannich derivatives [6]. A variety of thioureas [7] can be easily prepared by the reaction of [1] with amines. The supported thioureas are directly and efficiently converted to 2-aminothiazole-5-carboxylates [8] by reaction with methyl 2-chloroacetoacetate.

Solution-Phase Bioconjugate Synthesis Using Protected Oligonucleotides Containing 3‘-Alkyl Carboxylic Acids

Protected oligonucleotides containing 3‘-alkyl carboxylic acids are obtained from a photolabile solid-phase synthesis support (1b). The protected oligonucleotides are efficiently conjugated (>80%) with amines in solution to yield products of high purity under mild reaction conditions. This method is particularly well-suited for the synthesis of oligonucleotide−peptide conjugates containing a covalent linkage between the 3‘ terminus of an oligonucleotide and the amino terminus of a peptide. High yields of nucleopeptides are obtained even when the peptide contains a hindered N-terminal amino acid.

ChemInform Abstract: Polymeric Supports for Solid Phase Synthesis

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Merrifield MicroTube TM reactors for solid phase synthesis

Polystyrene grafted polypropylene MicroTube TM reactors (length × OD, 25 × 5 mm) have been functionalized with chloromethyl groups (Merrifield-type) using chloromethyl methyl ether and Lewis acid catalysts. A potentiometric method using a chloride ion selective electrode has been developed to measure the loading of the Merrifield MicroTube TM reactors. A typical loading of 25–35 μmol/tube for Merrifield MicroTube TM reactors has been achieved. Several reactions performed on Merrifield MicroTube TM reactors demonstrated that they are excellent supports for solid phase synthesis. As a result of the ease with which radiofrequency memory tags can be associated with and separated from the supports, these MicroTube TM reactors can facilitate the synthesis of combinatorial libraries.

Polymeric supports for solid phase synthesis

The nature of the polymer support plays an integral role in solid phase organic synthesis. Combinatorial and highly parallel synthetic strategies have stimulated the development of new polymer support materials with compositions and properties that allow a broader spectrum of organic transformations. Extension of solid phase organic synthesis to encoded microreactors provides an efficient methodology for preparing large numbers of discrete compounds.

Postsynthetic Conjugation of Protected Oligonucleotides Containing 3‘-Alkylamines

The expansion of a highly efficient, convergent method for synthesizing 3‘-oligonucleotide conjugates is described. 3‘-Oligonucleotide conjugates containing amide or urea linkages between the oligonucleotide portion and the conjugated species were obtained by reacting protected oligonucleotides containing 3‘-alkylamines in aprotic organic solvents with carboxylic acid and isocyanate substrates, respectively. The protected oligonucleotides are obtained via standard automated synthesis on a photolabile solid-phase synthesis support. Excellent yields (83−100%) of bioconjugates were obtained using carboxylic acids and aryl isocyanates with as few as 5 molar equivalents of conjugation reagents relative to protected oligonucleotide. More moderate yields were obtained using alkyl isocyanates as substrates (70−88%). In addition, this method has proven to be useful for synthesizing complementary oligonucleotide−peptide conjugates from a single oligonucleotide, in which the polarity of the peptide with respect to t...