Solid-phase synthesis of benzothiazoles using an alkoxyamine linker

An alkoxyamine linker was applied for the solid-phase synthesis of benzothiazoles. The substrate was anchored by aldoxime linkage and products were cleaved from the solid-support by aldoxime-imine exchange coupled with air-oxidation under the weakly acidic conditions. The tether is highly robust under Mitsunobu reaction, nucleophilic substitution reaction, and Pd-catalyzed reaction conditions.     

Solid-phase synthesis of phthalocyanine and tetraazaporphyrin triangular prisms

A solvent-free, solid-phase one-step reaction between tetra-tert-butylated oxotitanium(IV) phthalocyanine and tetraazaporphyrin with 2,3,6,7,10,11-hexahydroxytriphenylene yields novel azaporphyrin cyclic trimers with triangular prismatic orientations. The fluorescence arising from the phthalocyanine and tetraazaporphyrin chromophores is significantly quenched upon trimerization.     

Solid-phase synthesis of isoquinolinones using Bischler-Napieralski cyclization

Isoquinolinone is a structural unit found in many natural products having various important biological activities. A traceless solid-phase synthetic approach has been developed to prepare isoquinolinone derivatives. This approach enables one to synthesize isoquinolinones having various moieties on benzene nuclei and also can produce derivatives with a proton on the amide nitrogen.     

Solid-phase carbohydrate synthesis via on-bead protecting group chemistry

Di- and tri-saccharides were synthesized on a solid phase. The procedure started with a non-protected sugar linked via either cysteine or glutamine to a polystyrene resin. Selective dimethoxytritylation chemistry and subsequent steps yielded a resin-bound acceptor that could be glycosylated to yield β1,6-linked disaccharides. Reiteration of the procedure produced the trisaccharide.     

Solid-phase synthesis of terminal oligonucleotide-phosphoramidate conjugates

A novel phosphoramidite, N,N-diisopropylamino-2-cyanoethyl-9-anthracenemethyl phosphoramidite 1, was prepared and coupled with the terminal 5′-hydroxyl of support-bound T₁₀ and the putative phosphite triester intermediate was subsequently reacted with iodine in the presence of either water or a series of primary and secondary amines. The reactivity of 1 compared to a previously reported benzyl phosphoramidite 2 was also investigated: oxidation of the product of coupling 2 with CPG-T₁₀-5′OH under aqueous conditions resulted in greater than 30% of the benzyl moiety being retained. In contrast, essentially complete loss of the 9-anthracenemethyl group was observed using 1 under the same conditions. Oligonucleotides modified with a terminal phosphate monoester, lipophilic, fluorescent or cationic groups were thus prepared.     

Solid-phase synthesis of metal-complex containing peptides

We report the synthesis of Fmoc protected single amino acid chelates (SAAC) and their metal complexes. The modified amino acids are suitable for solid-phase peptide synthesis. The use of 4-hydroxymethylbenzoic acid AM (HMBA-AM) resin allows the nucleophilic cleavage of the peptide-metal complexes from the resin without decomplexation.     

Solid-phase synthesis of benzazoles,quinazolines, and quinazolinones using an alkoxyamine linker

An alkoxyamine linker was applied for the solid-phase synthesis of benzazoles, quinazolines, and quinazolinones. Aromatic aldehydes were anchored by aldoxime linkage. After some reactions on a solid support, the products were cleaved with paraformaldehyde under the acidic conditions to afford the corresponding aldehydes, which were subsequently subjected to oxidative coupling with 2-substituted anilines under air atmosphere to give the desired compounds.     

Solid-phase synthesis of lamellarins Q and O

An efficient solid phase synthesis of the pyrrole-based alkaloids lamellarins Q and O using Merrifield resin and N-protected methyl 3,4-dibromopyrrole-2-carboxylate as a scaffold is described.     

Combinatorial synthesis of amino acid- and peptide-carbohydrate conjugates on solid phase

Carbohydrates are useful polyfunctional scaffold molecules which allow the selective attachment of a number of different side chains. The combinatorial solid phase synthesis of diverse amino acid or peptide conjugates of a polyfunctional glucose scaffold based on a set of selectively removable and orthogonally stable protecting groups is described. The resulting carbohydrate-peptide hybrids constitute potential turn mimetics.     

Solid-phase synthesis of a type II′ β-turn peptido-mimetic library

The solid-phase synthesis of a dipeptide derived 2-amino-3-oxohexahydroindolizino[8,7-b]indole-5-carboxylate system (IBTM) is described. The IBTM moiety is formed via a solid-phase mediated Pictet-Spengler reaction of N-terminal tryptophan and the 4-{N-[1-(4,4-dimethyl-2,6-dioxocyclohexylidene)-3-methylbutyl]amino}benzyl (Dmab) ester of Fmoc protected aspartic acid β-aldehyde followed by γ-lactamization. This synthesis allows the regio- and stereoselective incorporation of a dipeptide surrogate of type II′ β-turns. The procedure is easily adaptable to combinatorial synthesis and a 576-member library was synthesized.     

Solid-phase synthesis of amidines by the reduction of amidoximes

Amidines can be prepared on a solid support by reducing polymer-bound amidoximes with SnCl₂·2H₂O. The method has proved to be straightforward and highly efficient. Amidoximes attached to the solid support are readily available by treating resin-bound nitriles with hydroxylamine.     

Solid-phase synthesis of palmitoylated and farnesylated lipopeptides employing the fluoride-labile PTMSEL linker

Acid- and base-labile S-palmitoylated and S-farnesylated lipopeptides can be synthesized in high overall yield employing the (2-phenyl-2-trimethylsilyl) ethyl (PTMSEL) linker for anchoring to and release under almost neutral conditions from the solid support.     

Solid-phase synthesis of 3-alkyl-2-arylamino-3,4-dihydroquinazolines

The solid-phase synthesis of 3-alkyl-2-arylamino-3,4-dihydroquinazolines using an N-Fmoc-β-amino-2-nitrobenzenepropanoic acid scaffold is described. The resin-bound scaffold was reductively alkylated with aldehydes or ketones after Fmoc deprotection, followed by reduction of the nitro group with tin(II) chloride. Subsequent cyclization of the 1,3-diamine intermediates with aryl isothiocyanates in the presence of 1,3-diisopropylcarbodiimide (DIC) afforded the desired products in high purity with moderate to good yield after trifluoroacetic acid (TFA) cleavage.     

Solid-phase synthesis of homodetic cyclic peptides from Fmoc-MeDbz-resin

Cyclic homodetic peptides are very appealing for medicinal chemistry programs. In addition to the high efficiency and selectivity inherently associated with peptides, a cyclic structure totally formed by amide bonds increases their stability under physiological conditions. Here Fmoc-MeDbz-resin was studied for the preparation of these peptides. Our results demonstrate the usefulness of this strategy for the preparation of cyclic “head-to-side chain” peptides through cyclative cleavage (simultaneous cyclization and release from the resin). In contrast, for the synthesis of the “head-to-tail” counterparts, the cyclization-cleavage should be carried out in the presence of thiophenol.     

Solid-phase synthesis of head and tail bis-acridinylated peptides

Amino-acridine conjugates play an important role as biochemical probes and/or drugs. Solid-phase synthesis of such compounds suitable for library construction and biological screening is described.     

Solid-phase synthesis of liquid crystalline isoxazole library

Combinatorial library of isoxazoles was prepared by 1,3-dipolar cycloaddition on solid support. p-Cyano derivatives showed nematic and/or smectic A phases. A bilayer smectic phase for 2h is proposed by the combination of molecular mechanics calculation and X-ray diffraction experiment.     

Solid-phase synthesis of polyfunctional polylysine dendrons using aldehyde linkers

A straightforward method for the solid-phase synthesis of C-terminally modified polylysine dendrons has been developed by applying bisalkoxybenzaldehyde and trisalkoxybenzaldehyde linkers. The method has been used for the synthesis of polylysine dendrons with a variety of C-terminal ‘tail groups’ such as alkyl, propargyl, and dansyl to give dendrons in high crude purity. Furthermore, the method was successful for the synthesis of dendrons with multiple N-terminal pentapeptide groups together with C-terminal alkyl and propargyl tail groups. Finally, the method was shown to be well-suited for automated synthesis.     

Solid-phase synthesis of quinoxaline derivatives using 6-amino-2,3-dichloroquinoxaline loaded on AMEBA resin

The solid-phase synthesis of quinoxaline derivatives 1 was accomplished through successive introduction of building blocks such as amines, methoxide, acid chlorides, and isocyanates into 6-amino-2,3-dichloroquinoxaline 2 loaded on AMEBA resin 3. The method made it possible to obtain the compound 1 in 63-100% purities and 36-89% isolated yields.     

Solid-phase synthesis of 6-hydroxy-2,4-diaminoquinazolines

A new method for the solid-phase synthesis of 6-hydroxy-2,4-diaminoquinazolines has been developed. The synthesis utilizes solid-phase bound 6-hydroxy-2,4-dichloroquinazoline as a key intermediate. Sequential substitution of the two chlorines furnishes the title compounds regioselectively with high purity. A library of 18×22 compounds demonstrates the general utility of this approach.     

Design and synthesis of a potent biotinylated Smac mimetic

A biotinylated Smac mimetic (2) was designed based upon our previously reported potent, conformationally constrained Smac mimetic (1). Smac mimetic (2) was synthesized and determined to bind to XIAP protein with a high-affinity (K_i value of 13 nM) and is therefore a useful pharmacological tool for probing the intracellular targets of this class of potent Smac mimetics.