The Current Status of Heterocyclic Combinatorial Libraries

High Throughput Synthesis of 2,3,6-Trisubstituted-5,6-Dihydroimidazo[2,1-b]thiazole Derivatives

A facile approach to the synthesis of 2,3,6-trisubstituted-5,6-dihydroimidazo[2,1-b]thiazole was reported. A resin bound cyclic thiourea was formed by the treatment of a resin bound diamine with 1,1'-thiocarbonyldiimidazole, and then reacted with a α-haloketone to generate a resin bound isothiourea. HF treatment of the resin bound isothiourea resulted in the cleavage of the product and simultaneous formation of an enamine bond. This led to the formation of the 2,3,6-trisubstituted-5,6-dihydroimidazo[2,1-b]thiazole in high yield and purity.

Multicomponent Reaction for the Synthesis of Pyridine Derivatives based on Triphenylamine

A facile preparation of pyridine derivatives based on triphenylamine through a multicomponent reaction from 3-cya-noacetylindoles, ammonium acetate and a 1,3-diarylpropenone either by conventional heating or microwave irradiation is described. The three-component reaction afforded good yields and involved a simple procedure.

Combinatorial Solid-Phase Synthesis of 6-Aryl-1,3,5-triazines via Suzuki Coupling

A synthetic methodology to prepare collections of trisubstituted aryl 1,3,5-triazines with broad structural diversity via Suzuki coupling has been developed. We first optimized the combinatorial derivatization of the triazine core using Suzuki cross-coupling. Second, in order to further expand the methodology for the preparation of negatively charged triazines, we adapted this approach to polymer-supported amino acids and prepared aryl triazines with different charge distribution. With a collection of 160 aryl triazine derivatives in good purities and without any purification step, we proved the viability of this orthogonal scheme for the preparation of triazine libraries using amine/amino acid-captured solid supports and Suzuki cross-coupling.

Identification of two novel, potent, low-liability antinociceptive compounds from the direct in vivo screening of a large mixture-based combinatorial library

Synthetic combinatorial methods now make it practical to readily produce hundreds of thousands of individual compounds, but it is clearly impractical to screen each separately in vivo. We theorized that the direct in vivo testing of mixture-based combinatorial libraries during the discovery phase would enable the identification of novel individual compounds with desirable antinociceptive profiles while simultaneously eliminating many compounds with poor absorption, distribution, metabolism, or pharmacokinetic properties. The TPI 1346 small-molecule combinatorial library is grouped in 120 mixtures derived from 26 functionalities at the first three positions and 42 functionalities at the fourth position of a pyrrolidine bis-cyclic guanidine core scaffold, totaling 738,192 compounds. These 120 mixtures were screened in vivo using the mouse 55 degrees C warm water tail-withdrawal assay to identify mixtures producing antinociception. From these data, two fully defined individual compounds (TPI 1818-101 and TPI 1818-109) were synthesized. These were examined for antinociceptive, respiratory, locomotor, and conditioned place preference effects. The tail-withdrawal assay consistently demonstrated distinctly active mixtures with analgesic activity that was blocked by pretreatment with the non-selective opioid antagonist, naloxone. Based on these results, synthesis and testing of TPI 1818-101 and 1818-109 demonstrated a dose-dependent antinociceptive effect three to five times greater than morphine that was antagonized by mu- or mu- and kappa-opioid receptor selective antagonists, respectively. Neither 1818-101 nor 1818-109 produced significant respiratory depression, hyperlocomotion, or conditioned place preference. Large, highly diverse mixture-based libraries can be screened directly in vivo to identify individual compounds, potentially accelerating the development of promising therapeutics.

Solution-phase synthesis of a diverse isocoumarin library

The solution-phase synthesis of a 167-member library of isocoumarins is described. The key intermediates for library generation, 4-iodoisocoumarins, are easily prepared by iodocyclization of the corresponding 2-(1-alkynyl)arenecarboxylate esters. The 4-iodoisocoumarins undergo palladium-catalyzed Sonogashira, Suzuki-Miyura, and Heck reactions to yield a diverse set of isocoumarins. Alternatively, isocoumarins, bearing hydroxyl or bromine functionalities, have been prepared by ZnCl(2)- and Pd(PPh(3))(4)-mediated cyclization of the corresponding o-iodobenzoic acid and appropriate terminal alkynes. The resulting isocoumarins were further diversified by derivatization of the hydroxyl or bromine groups. A small set of isoquinolinones were also prepared from the corresponding isocoumarins.

Palladium- and copper-catalyzed solution phase synthesis of a diverse library of isoquinolines

The solution-phase synthesis of a 111 member isoquinoline library is described. The isoquinoline scaffold has been accessed through the palladium- and copper-catalyzed cyclization of iminoalkynes and the palladium-catalyzed iminoannulation of internal alkynes, followed by diversification of hydroxyl functionality where it is present.

Solid-phase synthesis of optically active substituted 2 aminofuranones using an activated carbonate linker

An efficient three-step solid-phase synthesis of diverse 3,5-disubstituted-2-aminofuranones has been developed. alpha-Hydroxy acids loaded on a nitrophenyl carbonate derivative of Wang resin are used as acylating agents for the C-acylation of active methylene compounds and the resulting intermediates provided, through a cyclative cleavage reaction, the desired product.

Highly substituted indole library synthesis by palladium-catalyzed coupling reactions in solution and on a solid support

3-Iodoindoles have been synthesized by the iodocyclization of N,N-dialkyl-o-(1-alkynyl)anilines, obtained by the Pd/Cu catalyzed coupling of terminal acetylenes with N,N-dialkyl-o-iodoanilines. These 3-iodoindoles undergo palladium-catalyzed Sonogashira and Suzuki coupling reactions to yield 1,2,3-trisubstituted indoles. These reactions have been applied to parallel library synthesis utilizing commercially available terminal acetylenes and boronic acids. The aforementioned chemistry has also been carried out on a chlorinated Wang resin as a solid support, affording 1,2,3,5-tetrasubstituted indoles after cleavage from the support. A diverse 42-member library of highly substituted indoles has been synthesized.

Diversity-oriented synthesis of benzimidazole, benzoxazole, benzothiazole and quinazolin-4(3H)-one libraries via potassium persulfate-CuSO4-mediated oxidative coupling reactions of aldehydes in aqueous micelles

Libraries of 2-substituted-benzimidazoles, benzoxazoles, benzothiazoles as well as quinazolin-4(3H)-ones were synthesized via potassium persulfate-CuSO(4)-mediated oxidative coupling of aldehydes with o-phenylenediamines, o-aminophenols, o-aminothiophenols, and anthranilamide, respectively, in aqueous micelles. The strategy opens a way for rapid generation of libraries of small heterocycles for biological screening. The reagent is commercially available, cheap, and highly chemoselective. The yields were superior in aqueous micelles to those in organic solvents. Short reaction times, large-scale synthesis, excellent chemoselectivity, excellent yields, as well as environmental friendliness are the main advantages of this diversity-oriented synthesis.