Fluorogenic PNA probes

• Tirayut Vilaivan

Beilstein J. Org. Chem. 2018, 14, 253–281, doi:10.3762/bjoc.14.17

• via the formation of high order complexes between PNA–dsDNA was also possible using a combination of PNA probes and CPP [122]. The use of a labeled PNA probe can be avoided by employing a fluorescence dye that can bind to PNA–DNA duplexes or triplexes, such as thiazole orange (TO) [123]. A

Halogen-containing thiazole orange analogues – new fluorogenic DNA stains

• Aleksey A. Vasilev,
• Meglena I. Kandinska,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• David Sucunza,
• Juan J. Vaquero,
• Obis D. Castaño,
• Stanislav Baluschev and
• Silvia E. Angelova

Beilstein J. Org. Chem. 2017, 13, 2902–2914, doi:10.3762/bjoc.13.283

• monomethine cyanine dyes 5a–d, which are analogues of the commercial dsDNA fluorescence binder thiazole orange (TO), have been synthesized. The synthesis was achieved by using a simple, efficient and environmetally benign synthetic procedure to obtain these cationic dyes in good to excellent yields

• fluorescence spectroscopy) and theoretical (DFT and TDDFT calculations) methods. Keywords: cyanine dyes; DFT calculations; green synthesis; nucleic acids; thiazole orange; Introduction Since the discovery by Lee and co-workers [1][2] that the old photographic dye thiazole orange, TO, (Scheme 1) has excellent

• properties as a fluorogenic noncovalent DNA or RNA binder, many representatives of this class of dyes have been developed [3][4][5][6][7]. Thiazole orange does not fluoresce in the free state in solution. Fluorescence appears when the rotation about the monomethine bridge between the two heterocyclic

Reactivity of bromoselenophenes in palladium-catalyzed direct arylations

• Aymen Skhiri,
• Ridha Ben Salem,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2017, 13, 2862–2868, doi:10.3762/bjoc.13.278

• employed to prepare 2-heteroarylated selenophenes; whereas, 2,5-dibromoselenophene generally gave 2,5-di(heteroarylated) selenophenes in high yields using both thiazole and thiophene derivatives. Moreover, sequential catalytic C2 heteroarylation, bromination, catalytic C5 arylation reactions allowed the

• allowed the coupling of several heteroaromatics such as thiazole, pyrrole, furan or imidazole derivatives with aryl bromides [36]. 2-Bromoselenophene, which was easily prepared by reaction of selenophene with N-bromosuccinimide [37], and 2-ethyl-4-methylthiazole were employed as model substrates for our

• -dibromoselenophene were found to tolerate both thiazole and thiophene derivatives (Scheme 3). The coupling of 3 equiv of thiazole derivatives with 2,5-dibromoselenophene in the presence of 2 mol % Pd(OAc)2 and KOAc as base gave the corresponding 2,5-diheteroarylated selenophenes 8 and 9 in 78% and 80% yields

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• wastes. Here we describe the extension of this α-bromination shuttle system to 2-aminobenzothiazoles as substrates to synthesize benzo[d]imidazo[2,1-b]thiazoles. The benzo[d]imidazo[2,1-b]thiazole backbone is found in many bioactive molecules and pharmaceutical compounds as evident by its use as

• of benzo[d]imidazo[2,1-b]thiazole is the condensation of 2-aminobenzothiazole with α-halo or tosyloxy ketone [47][48]. The requirement for prior functionalization of the ketone moiety is a drawback, and several more direct methods have been developed in recent years [49][50][51][52]. Zhang et al

• the benzo[d]imidazo[2,1-b]thiazole derivatives via coupling of 2-aminobenzothiazole with the brominated β-ketoesters and amides. Over the past decade, there has been a lot of interest in KOt-Bu-mediated synthesis, especially after Itami’s group showed that KOt-Bu provides a metal-free approach to the

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• synthesis under mechanochemical conditions. Phosphonylation of benzothiazole and thiazole derivatives were done with organophosphorus compounds using 3 equiv of Mn(OAc)3·2H2O in a mixer mill for 1.5 h. Benzothiazole or thiazole rings having electron-donating or -withdrawing groups worked efficiently under

Synthesis of the heterocyclic core of the D-series GE2270

• Christophe Berini,
• Thibaut Martin,
• Pierrik Lassalas,
• Francis Marsais,
• Christine Baudequin and
• Christophe Hoarau

Beilstein J. Org. Chem. 2017, 13, 1407–1412, doi:10.3762/bjoc.13.137

• as readily available starting material. Keywords: antibiotic; bromination; BSC; C–H arylation; cross-coupling; Hantzsch synthesis; thiopeptide; Introduction Thiopeptide antibiotics are a class of peptide-derived macrocycles which contain many thiazole and thiazoline units, with almost 90 structures

• thiazole units using cross-coupling reactions and Hantzsch-type condensation to a pyridine central platform. This second strategy has been first initially explored by Kelly in 1991 for the first preparation of heterocyclic core of micrococcinic acid [12][13] but due to the unique and original mode of

• within five Hantzsch thiazole building steps [14]. Nicolaou and Moody reported then the synthesis of the heterocyclic core of GE2270 by using a late-stage [4 + 2] cycloaddition of a sophisticated bithiazolylazadiene with alkynylated thiazole [15][16]. As highly innovative strategy, Bach reported in 2005

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• characteristic (Z,Z,E)-triene, a thiazole side chain and a characteristic sequence of eight methyl and hydroxy-bearing stereocenters. Synthetic chemistry is of key importance to enhance the supply of these scarce polyketides to fully evaluate the biological potential and develop them as potential drug candidates

• suitable olefination strategy. Subsequently, for connecting the resulting fragment to the thiazole subunit 6 a Heck reaction was envisioned as part of studies advancing this type of Palladium-catalyzed coupling strategies in complex target synthesis [61][62][63][64][65][66]. Finally, a HWE-macrocyclization

• -intermediate [76]. After conversion to amide 28 and thioamide 29 the thiazole 31 was obtained by condensation with bromoester 30. The carbamate was then introduced by activation of the deprotected hydroxy group with carbonyldiimidazole and treatment with methylamine, before the ester was selectively reduced to

N-Propargylamines: versatile building blocks in the construction of thiazole cores

• S. Arshadi,
• E. Vessally,
• L. Edjlali,
• R. Hosseinzadeh-Khanmiri and
• E. Ghorbani-Kalhor

Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61

• reactions to produce various nitrogen-containing heterocycles. In this review, we highlight the most important developments on the synthesis of thiazole and its derivatives starting from N-propargylamines. This review will be helpful in the development of improved methods for the synthesis of natural and

• ]. As a consequence, many routes for the synthesis of thiazole derivatives are reported in the literature [26][27][28][29][30][31][32][33]. Among them, the Hantzsch thiazole synthesis (condensation of α-haloketones with thioamides) is the most efficient and straight forward procedure [34][35][36][37][38

• important developments on the synthesis of thiazole and its derivatives from N-propargylamines (Figure 3) which will be helpful in the development of improved methods for the synthesis of natural and biologically important compounds. The review is organized by the type of starting materials. Review 1 From N

Derivatives of the triaminoguanidinium ion, 5. Acylation of triaminoguanidines leading to symmetrical tris(acylamino)guanidines and mesoionic 1,2,4-triazolium-3-aminides

• Jan Szabo,
• Julian Greiner and
• Gerhard Maas

Beilstein J. Org. Chem. 2017, 13, 579–588, doi:10.3762/bjoc.13.57

• is supported inter alia by recent theoretical studies using DFT calculations, Natural Bond Orbital analysis and Natural Resonance Theory calculations for mesoionic systems of the 1,3-oxazole, 1,3-diazole and 1,3-thiazole type [39]. As 1,2,4-triazolium-3-aminides have not yet been studied in depth

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• quaternary center with high diastereoselectivity as a consequence of the Stetter–Aldol–Aldol (SAA) reaction sequence. The Stetter–Aldol–Aldol conversion of the phthaldialdehyde derivatives 75 and o-formyl substituted chalcones 76 using the thiazole based carbene 78 as a precatalyst allowed to obtain spiro

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• ): calcd for [C17H29BrO]+: 351.1294; found: 351.1299. 3-[6-{(Adamantan-1-yl)methoxy}hexyl]-2-methylbenzo[d]thiazole (2) Methylbenzothiazole (0.89 g, 6 mmol) and 1-[{(6-bromohexyl)oxy}methyl]adamantane (1, 1.97 g, 6 mmol) were dissolved in 4 mL of acetonitrile and the resulted solution was stirred at 90 °C

Dinuclear thiazolylidene copper complex as highly active catalyst for azid–alkyne cycloadditions

• Anne L. Schöffler,
• Ata Makarem,
• Frank Rominger and
• Bernd F. Straub

Beilstein J. Org. Chem. 2016, 12, 1566–1572, doi:10.3762/bjoc.12.151

• -heterocyclic carbene, linker, sacrificial ligand, and counter ion. Keywords: catalysis; click; copper; CuAAC; N-heterocyclic carbene; thiazole; Introduction The copper-catalyzed azide–alkyne cycloaddition (CuAAC) is one of the most important “click” reactions for the facile covalent linking of two molecules

• less time-consuming and more cost-efficient synthesis. Commercially available, inexpensive 4,5-dimethylthiazole is used as azole starting material instead of 4-aryl-1,2,4-triazoles. The precursor 1a for the NHC ancillary ligand is synthesized via a double SN2-reaction of two equivalents of thiazole

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

Application of Cu(I)-catalyzed azide–alkyne cycloaddition for the design and synthesis of sequence specific probes targeting double-stranded DNA

• Svetlana V. Vasilyeva,
• Vyacheslav V. Filichev and
• Alexandre S. Boutorine

Beilstein J. Org. Chem. 2016, 12, 1348–1360, doi:10.3762/bjoc.12.128

• -NH2 and two fluorophores bearing an azide functional group: one cyanine TO (derivative of thiazole orange [18]), and one coumarine MM14 kindly provided by M. P. Teulade-Fichou (Figure 7). The conjugation was conducted in a microwave reactor as for the polyamide tandem synthesis [2]. The details of the

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

• Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

• pathways but is found across proteins of all sizes so will not be discussed here. Review Thiazole and oxazoles Thiazoles and oxazoles are found in a huge number of bacterial RiPPs, which are often loosely defined as thiazole/oxazole-modified microcins [24] (TOMMs), although these can be subdivided more

• there remains a wealth of unexplored pathways to discover and characterise. Schematic of RiPP biosynthesis. Thiazole/oxazole formation is represented by the blue heterocycle (X = S, O), lanthionine formation is represented by the purple cross-link (X = S) and macrolactam (X = N) or macrolactone (X = O

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• β-enol (10) [48]. Otherwise, it appears in the range δ 140.6–143.3 if C-8 bears a phenol group (compounds 3, 4, 6–8, 13, and 14) [45][46][50]. Likewise, the same downfield resonances have been found for C-6, when C-7b and its neighboring carbons C-10a or C-11a form a thiazole (see compounds 20–26

• synthesized as shown in Scheme 12. Its structure differs from that of the natural product 60 by the substitution of the thiazole ring in kuanoniamine A (60) with an aryl ring (Scheme 12) [73]. Biosynthesis The biosynthesis of pyridoacridine alkaloids has been poorly investigated and reported with only a few

• tryptophan and dopamine as precursors of pyridoacridines. Thus, formaldehyde and amino acids are responsible for the thiazole, piperidone, oxathiolane and thiomorpholinone rings found in pyridoacridines structures. Biological activity The biological activity of pyridoacridines, including both natural and

Thiazole-induced rigidification in substituted dithieno-tetrathiafulvalene: the effect of planarisation on charge transport properties

• Rupert G. D. Taylor,
• Joseph Cameron,
• Iain A. Wright,
• Neil Thomson,
• Olena Avramchenko,
• Alexander L. Kanibolotsky,
• Anto R. Inigo,
• Tell Tuttle and
• Peter J. Skabara

Beilstein J. Org. Chem. 2015, 11, 1148–1154, doi:10.3762/bjoc.11.129

• Physical-Organic Chemistry and Coal Chemistry, 02160 Kyiv, Ukraine 10.3762/bjoc.11.129 Abstract Two novel tetrathiafulvalene (TTF) containing compounds 1 and 2 have been synthesised via a four-fold Stille coupling between a tetrabromo-dithienoTTF 5 and stannylated thiophene 6 or thiazole 4. The optical

• demonstrated that the substitution of thiophene units for thiazoles was found to increase the observed charge transport, which is attributed to induced planarity through S–N interactions of adjacent thiazole nitrogen atoms and TTF sulfur atoms and better packing in the bulk. Keywords: non-covalent

• interactions; organic field effect transistor (OFET); organic semiconductors; tetrathiafulvalene; thiazole; Introduction The TTF moiety has received much attention in the field of organic electronics owing to its reliable redox behaviour [1], good charge transport properties [2] and scope for

Thiazole formation through a modified Gewald reaction

• Carl J. Mallia,
• Lukas Englert,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 875–883, doi:10.3762/bjoc.11.98

• substitution of the α-carbon to the cyano group. Keywords: design of experiment (DOE); 1,4-dithiane-2,5-diol; Gewald reaction; thiazole; thiophene; Introduction Thiazoles are privileged motifs which are encountered in many naturally occurring bioactive compounds and pharmaceuticals with indications in a

• synthesis protocol, the Hantzsch synthesis, requires access to appropriately functionalised α-halocarbonyls but such starting materials are not always readily available. Consequently, expanding the scope of thiazole synthesis by developing new methodologies remains an active area of research. The air-stable

• with the aldehyde derived from 10. Although the thiazole formation from nitriles has already been shown to occur with ketones [23][24][25][26] and carboxylic acid [27][28] derivatives to give 2,5-disubstituted thiazoles, to our knowledge aldehydes have only been shown to form 2-aminothiophenes [29

Synthesis and chemosensing properties of cinnoline-containing poly(arylene ethynylene)s

• Natalia A. Danilkina,
• Petr S. Vlasov,
• Semen M. Vodianik,
• Andrey A. Kruchinin,
• Yuri G. Vlasov and
• Irina A. Balova

Beilstein J. Org. Chem. 2015, 11, 373–384, doi:10.3762/bjoc.11.43

• ][17][18]. Moreover, various species of` PAEs with quinoline [19][20], quinoxaline [21][22], thiadiazole [17][23], carbazole [18][24], 1,2,4-triazoles [25], thiazole [26] and azametallocyclic [27] units incorporated into a polymer chain have been described. Since ligands based on pyridazine rings can

A comparative study of the interactions of cationic hetarenes with quadruplex-DNA forming oligonucleotide sequences of the insulin-linked polymorphic region (ILPR)

• Darinka Dzubiel,
• Heiko Ihmels,
• Mohamed M. A. Mahmoud and
• Laura Thomas

Beilstein J. Org. Chem. 2014, 10, 2963–2974, doi:10.3762/bjoc.10.314

• -b′′′]tetraquinolizinium (5) and thiazole orange (6) were studied. It is demonstrated with absorption, fluorescence and CD spectroscopy that all investigated ligands bind with relatively high affinity to the ILPR-quadruplex DNA a2 (0.2–5.5 × 106 M−1) and that in most cases the binding parameters of

• case of thiazole orange (6) whose emission intensity increases by a factor of I/I0 = 1766. Within the series of heptamethine cyanine dyes 1a–e, the derivative 1d exhibits the largest light-up factor with I/I0 = 128. In contrast, the emission of coralyne (2), bis-quinolinium derivative 3 and the

• with the telomeric quadruplex 22AG (Table 2). For example, the cyanine derivative 1e shows the most significant difference between the binding affinity towards ILPR and the telomeric quadruplex (a2: Kba2 = 1.7 × 107 M−1; 22AG: Kb22AG = 3.9 × 105 M−1). Although thiazole orange (6) has a relatively high

Palladium-catalyzed 2,5-diheteroarylation of 2,5-dibromothiophene derivatives

• Fatma Belkessam,
• Aidene Mohand,
• Jean-François Soulé,
• Abdelhamid Elias and
• Henri Doucet

Beilstein J. Org. Chem. 2014, 10, 2912–2919, doi:10.3762/bjoc.10.309

• product 2 in 82% yield. It should be noted that no arylation at C2 of this thiazole derivative was observed. Then, a set of thiophene derivatives was employed. Both, 2-methyl- and 2-chlorothiophenes afforded the desired products 3 and 4 in good yields in the presence of PdCl(C3H5)(dppb) as the catalyst

• was expected, as they are known to be less reactive than thiazole derivatives [44]. Moderate yields for 5 and 6 were obtained starting form thiophene-2-carbonitrile and ethyl thiophene-2-carboxylate, respectively in the presence of 2 mol % PdCl(C3H5)(dppb) catalyst due to the formation of unidentified

• in 62% yield. The arylation at C4 of 3,5-dimethylisoxazole and 5-chloro-1,3-dimethylpyrazole also proceeded nicely to give 29 and 30 in 66% and 72% yield, respectively. It should be noted that, for the synthesis of 24, the introduction of the thiazole unit in the first step (Scheme 1 and Scheme 4, 36

A small azide-modified thiazole-based reporter molecule for fluorescence and mass spectrometric detection

• Stefanie Wolfram,
• Hendryk Würfel,
• Stefanie H. Habenicht,
• Christine Lembke,
• Phillipp Richter,
• Eckhard Birckner,
• Rainer Beckert and
• Georg Pohnert

Beilstein J. Org. Chem. 2014, 10, 2470–2479, doi:10.3762/bjoc.10.258

• synthesis and application of the new thiazole-based, azide-tagged reporter 4-(3-azidopropoxy)-5-(4-bromophenyl)-2-(pyridin-2-yl)thiazole for fluorescence, UV and mass spectrometry (MS) detection. This small fluorescent reporter bears a bromine functionalization facilitating the automated data mining of

• also used for probing in life science comprises the heterocyclic thiazoles. This structural element can be found in commercial products, such as thiazole orange, SYBR® Green I or TOTO®, which are, e.g., used for DNA labeling. In these compounds the thiazole ring is part of a benzothiazole. We set out

• to minimize the structural complexity of the fluorophores to achieve higher atom economy and reduce the interaction with biomacromolecules. In this context it was critical to realize that the thiazole moiety itself can also act as a fluorophore, especially the class of 4-hydroxythiazoles [4][5]. 4

Facile synthesis of 1H-imidazo[1,2-b]pyrazoles via a sequential one-pot synthetic approach

• András Demjén,
• Márió Gyuris,
• János Wölfling,
• László G. Puskás and
• Iván Kanizsai

Beilstein J. Org. Chem. 2014, 10, 2338–2344, doi:10.3762/bjoc.10.243

• -aminoazoles, including thiazole [13][14] and 1,3,4-thiadiazole [15][16] derivatives, or 2-aminoazine-based heterocycles, such as pyridines [17][18][19], pyrimidines [20][21][22][23][24] and pyrazines [25][26][27], have recently been utilized as Groebke–Blackburn–Bienaymé three-component reaction (GBB-3CR

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• expected compound 109 (Scheme 34). Thiazoles In several natural products, the thiazole ring can be found as a backbone linker, probably resulting from easy cyclization/oxidation of cysteine residues. These compounds show interesting antifungal and antibiotic [95][96], algicidal [97], and antitumor [98][99

• ] biological activities. In addition, thiazole-based pharmaceuticals are also used as anti-prion agents (neurodegenerative disorders) [100]. Dömling and co-workers were the first that reported an Ugi-based synthesis of 2,4-disubstituted thiazoles (Scheme 35) [101][102]. The procedure involved a condensation of

• tautomerizes, the authors proposed a plausible mechanism, in which tautomer 113 undergoes cyclization via an intramolecular Michael reaction to give intermediate 114. The next step involves cleavage of the dimethylamine group to afford the thiazole structures 115. In 2003, the same group also described a solid

Total synthesis and cytotoxicity of the marine natural product malevamide D and a photoreactive analog

• Werner Telle,
• Gerhard Kelter,
• Heinz-Herbert Fiebig,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2014, 10, 316–322, doi:10.3762/bjoc.10.29

• was still active, because it had been shown in several SAR studies that limited variation of the amine or alcohol component at the C-terminal amide or ester moieties of the dolastatin family members can be tolerated without much loss of cytotoxicity. This includes epimerization of the thiazole

• -carrying stereocenter of 3 [18], replacement of the phenyl by a methyl group, or removal of the thiazole ring [7]. Auristatins, of which some undergo clinical trials, are characterized by lacking the thiazole ring of 3 [19]. Pettit and co-workers prepared auristatin TP, which carries a phosphate unit in