From chemical metabolism to life: the origin of the genetic coding process

• Antoine Danchin

Beilstein J. Org. Chem. 2017, 13, 1119–1135, doi:10.3762/bjoc.13.111

• convincing way [31]. Other coenzymes, possibly generated by such a swinging-arm thioester-dependent catalysis, may have been precursors of nucleotides, the essential building blocks of nucleic acids. As a matter of fact, extant biosynthesis of nucleotides (built on purine and pyrimidine carbon–nitrogen

• aromatic heterocycles) is based on the incorporation of amino acids in the core of nucleotide precursors. Pyrimidine nucleotide biosynthesis uses aspartate and combines together ubiquitous molecules, water, carbon dioxide, ammonium and phosphate (forming carbamoyl phosphate, also a precursor of arginine

Nucleophilic displacement reactions of 5′-derivatised nucleosides in a vibration ball mill

• Olga Eguaogie,
• Patrick F. Conlon,
• Francesco Ravalico,
• Jamie S. T. Sweet,
• Thomas B. Elder,
• Louis P. Conway,
• Marc E. Lennon,
• David R. W. Hodgson and
• Joseph S. Vyle

Beilstein J. Org. Chem. 2017, 13, 87–92, doi:10.3762/bjoc.13.11

• reactions require the use of high-boiling, dipolar aprotic solvents and anionic nucleophiles under anhydrous conditions at elevated temperatures (up to 150 °C). Competing intramolecular cyclisation reactions between both purine and pyrimidine nucleobases and (especially) the 5′-position of the (deoxy

• were observed with IdT (1d) and IdG (1e) although maximal conversion of IdG was achieved within one hour in the absence of added liquid (the reaction was inhibited in the presence of DMF). During these studies, LAG of both purine and pyrimidine substrates in the presence of ethyl acetate or hexane was

Enzymatic synthesis and phosphorolysis of 4(2)-thioxo- and 6(5)-azapyrimidine nucleosides by E. coli nucleoside phosphorylases

• Vladimir A. Stepchenko,
• Anatoly I. Miroshnikov,
• Frank Seela and
• Igor A. Mikhailopulo

Beilstein J. Org. Chem. 2016, 12, 2588–2601, doi:10.3762/bjoc.12.254

• comparison with the natural pyrimidine nucleosides in order to understand the impact of such modifications as monomers or constituents of oligonucleotides [8][9][10][11][12][13][14]. Thioxopyrimidine nucleosides as such, as well as building blocks of artificial oligonucleotides demonstrate promising

• antiviral activity in various experiments [15][16][17][18][19][20][21][22]. Regarding the chemical synthesis of this class of pyrimidine nucleosides various approaches were published (see, e.g., [8][9][10][11][14][15][16][23][24]; reviewed by Vorbrüggen and Ruh-Pohlenz [25]). On the contrary, only few

• 2.4.2.4) phosphorylases [36], and (ii) the role of structural features and electronic properties of the pyrimidine bases and nucleosides in the recognition by E. coli nucleoside phosphorylases. Results and Discussion Thioxo- and 6-aza-pyrimidines used in the transglycosylation reaction with recombinant E

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• dihydropyridine, hydantoin, imidazole, indole, isoquinoline, isoxazole, oxazole, 4H-pyran, pyrazine, pyridazine, pyridine, pyridinone, pyrimidine, pyrimidone, pyrrole, 3H-quinazolin-4-one, quinoline, 1H-quinolin-4-one, and thiophene. For heterocycles that are composed of a fused aromatic ring, such as

Methylpalladium complexes with pyrimidine-functionalized N-heterocyclic carbene ligands

• Dirk Meyer and
• Thomas Strassner

Beilstein J. Org. Chem. 2016, 12, 1557–1565, doi:10.3762/bjoc.12.150

• Dirk Meyer Thomas Strassner Physikalische Organische Chemie, TU Dresden, Bergstraße 66, 01062 Dresden, Germany 10.3762/bjoc.12.150 Abstract A series of methylpalladium(II) complexes with pyrimidine-NHC ligands carrying different aryl- and alkyl substituents R ([((pym)^(NHC-R))PdII(CH3)X] with X

• -NHC ligand [33]. To study the differences between both systems we synthesized palladium [34] and platinum [35] “hybrid complexes” with ligands combining both structural elements the pyrimidine as well as the NHC fragment. We also used density functional theory (DFT) calculations to investigate the

• different donor character. The experimentally determined geometrical parameters are in good agreement with the computed results. Interestingly, complexes 9, 10 and 12 show only one discrete doublet for the m-pyrimidine proton signals in the 1H NMR spectrum in DMSO-d6 indicating that the pyrimidine ring

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• alkoxyallene [46][47]. As mentioned above β-ketoenamide 3i is a good precursor for 2,2´-bipyridine derivative 4i, but Scheme 4 also reveals that this intermediate could be converted into the expected pyrimidine derivative 7 by treatment with ammonium acetate [48][49][50] or into pyrimidine N-oxide 8 by

• methoxylation of compound 3a we unexpectedly observed the formation of the 5-acetyl-substituted oxazole derivative 6. However, precursor 3i was smoothly available from acetylacetone 1a. It could smoothly be transformed into the desired bipyridine derivative 4i, but also into the related pyrimidine and

• pyrimidine N-oxide derivatives 7 and 8. Altogether, we could confirm that our approach to functionalized pyridine derivatives by cyclocondensation of β-ketoenamides is also a very versatile and flexible method for the synthesis of unsymmetrically substituted bipyridine derivatives or related heterocyclic

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

• Sebastian Bretzke,
• Stephan Scheeff,
• Felicitas Vollmeyer,
• Friederike Eberhagen,
• Frank Rominger and
• Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

• -metathesis of a challenging homoallylic urea substrate, which proceeds in good yields in the presence of an organic phosphoric acid. Keywords: cross-metathesis; natural products; pyrimidines; Tsuji–Trost reaction; synthetic methods; Introduction Chiral pyrimidine motifs constitute prevalent structural

• allylic substitution reaction of a joint precursor 5. Subsequently this strategy is successfully applied to the synthesis of the authentic pyrimidine cores 3 and 4 of manzacidin A (1) and ent-manzacidin C (2). Results and Discussion General synthetic concept As part of our ongoing efforts to the design of

The role of alkyl substituents in deazaadenine-based diarylethene photoswitches

• Christopher Sarter,
• Michael Heimes and
• Andres Jäschke

Beilstein J. Org. Chem. 2016, 12, 1103–1110, doi:10.3762/bjoc.12.106

• -based photoswitchable nucleosides. The design of these molecules challenged two of the established design rules for diarylethene-based photoswitches (Figure 1C) [45]: (1) They incorporated a six-membered pyrimidine ring, and (2) – more importantly – only one methyl group, rather than two, was present at

• are compared. Therefore, we set out to clarify this matter. If pyrimidine-based diarylethenes with one methyl group are good photoswitches, purine derivatives might work as well with just one methyl group. If this hypothesis was true, the synthesis of such photoswitches would be much simplified

• diarylethenes by direct comparison, and ii) we wanted to test whether our prior successful violation of this “rule” with photochromic pyrimidine nucleosides could be expanded to purine nucleosides. Our analysis reveals that – depending on the substituents – the one-methyl 7-deaza-2’-deoxyadenosine compounds can

Bi- and trinuclear copper(I) complexes of 1,2,3-triazole-tethered NHC ligands: synthesis, structure, and catalytic properties

• Shaojin Gu,
• Jiehao Du,
• Jingjing Huang,
• Huan Xia,
• Ling Yang,
• Weilin Xu and
• Chunxin Lu

Beilstein J. Org. Chem. 2016, 12, 863–873, doi:10.3762/bjoc.12.85

• [1][2][3][4][5][6][7][8][9][10][11][12]. A number of transition metal complexes of NHCs containing pyridine [13], pyrimidine [14], pyrazole [15][16], naphthyridine [17], pyridazine [18], and phenanthroline [19][20] donating groups have been studied in metal-catalyzed organic transformations. Recently

• excess of copper powder in CH3CN at 50 °C for 5 h. As shown in Scheme 1, reactions of the pyrimidine imidazolium salt 1a with copper powder in acetonitrile afforded a light yellow Cu(II) complex. In complex 2, the carbenic carbon atom was oxidized into carbonyl, which is similar with the reported

• two L2 ligands. The two ligands are arranged in head-to-tail manner. The copper ions are each tri-coordinated by one carbene carbon atom, one nitrogen from pyrimidine, and one nitrogen atom of the triazole rings from two different L2 ligands. The Cu–carbene bond distances are 1.896(6) and 1.899(5) Å

Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions

• Vito Rizzi,
• Sergio Matera,
• Paola Semeraro,
• Paola Fini and
• Pinalysa Cosma

Beilstein J. Org. Chem. 2016, 12, 549–563, doi:10.3762/bjoc.12.54

• presence of CDs to prevent its degradation under irradiation. UV–vis, FTIR–ATR and CV measurements suggested the formation of supramolecular structures involving the employed CDs and mainly the pyrimidine ring of S4TdR. 1H NMR analyses confirmed such indication, unveiling the presence of inclusion

• related to a π–π* transition into the second lowest excited singlet (S2) state of the molecule. As a result, the delocalized electrons on the pyrimidine ring were supposed to be involved in a transition having a charge transfer character [26]. Taking this into account and with the prospect of an

• through a re-organization of solvating water molecules. Undoubtedly, a combination of these two effects could be considered. At this point, since the obtained UV–vis results are not sufficiently clear to definitely prove the formation of S4TdR/CDs inclusion complexes, in which the pyrimidine ring is

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• results, the high association constant observed with γ-CD is mainly due to a good fitting of the pyrimidine ring into the cavity, while one ethoxy substituent protruding from the lower rim. In the cases of α- and β-CD, the phosphoryl residue is located outside the cavity. For α- and β-CD, the methyl

Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

• Hans Sterckx,
• Johan De Houwer,
• Carl Mensch,
• Wouter Herrebout,
• Kourosch Abbaspour Tehrani and
• Bert U. W. Maes

Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16

• these more challenging substrates. Interestingly, phenyl(quinolin-2-yl)methanone (6a) and phenyl(quinolin-4-yl)methanone (6b) were formed in moderate yields indicating that larger aromatic systems are compatible with the reaction conditions. In the case of 2-(4-chlorobenzyl)pyrimidine (5c) the standard

• ) could be obtained in 92% yield. In contrast to the two former cases, 4-(4-chlorobenzyl)pyrimidine (5e) could neither be oxidized at 100 °C nor at 130 °C. Competitive C–H activation of the 2 position is presumed to be the reason for this observation. Blocking this position by a methyl group (5f

A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

• Steven C. Zimmerman

Beilstein J. Org. Chem. 2016, 12, 125–138, doi:10.3762/bjoc.12.14

• analog 26) showed high selectivity in binding pyrimidine mismatches [48]. The affinity of 26 for a TT mismatch in DNA was sufficient to inhibit the binding M. TaqI and, thus, potentially interfere with mismatch repair enzymes that have been implicated in certain diseases [49]. In 2009, Brent Iverson and

Recent advances in copper-catalyzed C–H bond amidation

• Jie-Ping Wan and
• Yanfeng Jing

Beilstein J. Org. Chem. 2015, 11, 2209–2222, doi:10.3762/bjoc.11.240

• heterocycle, the pyrimidine ring was disclosed as useful DG in copper-catalyzed C–H activation. As reported by Shen and co-workers [60], the C–H bond in indoles 47 and benzenes 48 could be effectively activated with copper in the presence of DGs such as pyrimidin-2-yl, pyridine-2-yl or benzoyl to provide

A convenient four-component one-pot strategy toward the synthesis of pyrazolo[3,4-d]pyrimidines

• Mingxing Liu,
• Jiarong Li,
• Hongxin Chai,
• Kai Zhang,
• Deli Yang,
• Qi Zhang and
• Daxin Shi

Beilstein J. Org. Chem. 2015, 11, 2125–2131, doi:10.3762/bjoc.11.229

• Mingxing Liu Jiarong Li Hongxin Chai Kai Zhang Deli Yang Qi Zhang Daxin Shi School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing, 100081, China 10.3762/bjoc.11.229 Abstract An efficient one-pot synthesis of pyrazolo[3,4-d]pyrimidine derivatives by the four

• -6-(2-nitrophenyl)-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine was determined by single crystal X-ray diffraction. Keywords: four-component; one-pot; pyrazolo[3,4-d]pyrimidine; sodium alkoxide; Introduction Heterocycles containing a pyrimidine ring are extensively present in natural products and are very

• catalyst (Table 1, entries 1 and 2). Sodium hydroxide could catalyze this reaction, but pyrazolo[3,4-d]pyrimidinone 5aa was obtained instead of pyrazolo[3,4-d]pyrimidine 5a (Table 1, entry 3). This shows that the catalytic properties of sodium hydroxide have some limitations. Fortunately, some strong bases

Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction

• Chao Chen,
• Chunxin Lu,
• Qing Zheng,
• Shengliang Ni,
• Min Zhang and
• Wanzhi Chen

Beilstein J. Org. Chem. 2015, 11, 1786–1795, doi:10.3762/bjoc.11.194

• , China 10.3762/bjoc.11.194 Abstract Ruthenium complexes [Ru(L1)2(CH3CN)2](PF6)2 (1), [RuL1(CH3CN)4](PF6)2 (2) and [RuL2(CH3CN)3](PF6)2 (3) (L1= 3-methyl-1-(pyrimidine-2-yl)imidazolylidene, L2 = 1,3-bis(pyridin-2-ylmethyl)benzimidazolylidene) were obtained through a transmetallation reaction of the

• corresponding nickel–NHC complexes with [Ru(p-cymene)2Cl2]2 in refluxing acetonitrile solution. The crystal structures of three complexes determined by X-ray analyses show that the central Ru(II) atoms are coordinated by pyrimidine- or pyridine-functionalized N-heterocyclic carbene and acetonitrile ligands

• ]. In continuation of our studies on functionalized Ru(II)–NHC complexes containing acetonitrile ligands, we herein report the synthesis and characterization of three pyrimidine- and pyridine-functionalized NHC–ruthenium complexes containing two, four, and three acetonitrile ligands, respectively. These

Indolizines and pyrrolo[1,2-c]pyrimidines decorated with a pyrimidine and a pyridine unit respectively

• Marcel Mirel Popa,
• Emilian Georgescu,
• Mino R. Caira,
• Florentina Georgescu,
• Constantin Draghici,
• Raluca Stan,
• Calin Deleanu and
• Florea Dumitrascu

Beilstein J. Org. Chem. 2015, 11, 1079–1088, doi:10.3762/bjoc.11.121

• Fundulea, Calarasi, Romania 10.3762/bjoc.11.121 Abstract The three possible structural isomers of 4-(pyridyl)pyrimidine were employed for the synthesis of new pyrrolo[1,2-c]pyrimidines and new indolizines, by 1,3-dipolar cycloaddition reaction of their corresponding N-ylides generated in situ from their

• corresponding cycloimmonium bromides. In the case of 4-(3-pyridyl)pyrimidine and 4-(4-pyridyl)pyrimidine the quaternization reactions occur as expected at the pyridine nitrogen atom leading to pyridinium bromides and consequently to new indolizines via the corresponding pyridinium N-ylides. However, in the case

• of 4-(2-pyridyl)pyrimidine the steric hindrance directs the reaction to the pyrimidinium N-ylides and, subsequently, to the formation of the pyrrolo[1,2-c]pyrimidines. The new pyrrolo[1,2-c]pyrimidines and the new indolizines were structurally characterized through NMR spectroscopy. The X-ray

Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties

• Emma Werz and
• Helmut Rosemeyer

Beilstein J. Org. Chem. 2015, 11, 913–929, doi:10.3762/bjoc.11.103

• positions of the pyrimidine β-D-ribonucleosides uridine (1, R = H), 5-methyluridine (2, R = CH3) and 5-fluorouridine (3, R = F) which were lipophilized by different hydrophobic residues. The following formulae (Figure 2) show the six nucleolipids 4a–9a [13][14][15][16][17], which designate that mono

• -, sesqui-, and diterpenes as well as single and double-chained alkyl groups (completed by an alicyclic alkyl group), have been introduced for the lipophilization of the pyrimidine nucleosides. The resulting nucleolipids were converted into their corresponding 2-cyanoethyl phosphoramidites 4b–9b. Figure 3

• pyrimidine β-D-ribonucleoside head groups 1–3 [18]. Chemical formulae 1–9 and lipo-oligonucleotide sequences 10–15. Energy-minimized 3D structures of the lipophilic nucleoside headgroups 4a–9a. All 3D structures were calculated using the program ChemBio3D Ultra v. 12.0 (number of iterations, 387 ± 147

Sequence-specific RNA cleavage by PNA conjugates of the metal-free artificial ribonuclease tris(2-aminobenzimidazole)

• Friederike Danneberg,
• Alice Ghidini,
• Plamena Dogandzhiyski,
• Elisabeth Kalden,
• Roger Strömberg and
• Michael W. Göbel

Beilstein J. Org. Chem. 2015, 11, 493–498, doi:10.3762/bjoc.11.55

• have only pyrimidine bases, while RNA 15 and 17 have mainly purine bases in the corresponding regions. If the tris(2-aminobenzimidazole) cleaver interacts with the purine bases (e.g., by stacking) it is not impossible that this could also be related to the apparent lower rate and lower selectivity in

• RNAs 15 or 17 under identical conditions (Supporting Information File 1). The relatively low site specificity, as discussed above, may be related to the pyrimidine rich sequence of RNA 16. To examine whether PNA conjugates 10–14 would form molecular aggregates with noncognate oligonucleotides, the

The reactions of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole as a way to novel azaheterocycles

• Marina V. Goryaeva,
• Yanina V. Burgart,
• Marina A. Ezhikova,
• Mikhail I. Kodess and
• Viktor I. Saloutin

Beilstein J. Org. Chem. 2015, 11, 385–391, doi:10.3762/bjoc.11.44

• substitution. The use of diethyl 2-ethoxymethylidenemalonate in this reaction resulted in ethyl 7-hydroxytetrazolo[1,5-a]pyrimidine-6-carboxylate, while ethyl 2-ethoxymethylidenecyanoacetate yielded 5-[2,6-diamino-3,5-bis(ethoxycarbonyl)pyridinium-1-yl]tetrazol-1-ide through an alternative pathway. Ethyl 2

• -benzoyl-3-ethoxyprop-2-enoate reacted with 5-aminotetrazole by two reaction routes to form ethyl 2-benzoyl-3-(1H-tetrazol-5-ylamino)prop-2-enoate and ethyl 7-(1-ethoxy-1,3-dioxo-3-phenylpropan-2-yl)-5-phenyl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate. Keywords: 5-aminotetrazole; cyclisation

• medical practice [1]. The possibility to generate pyrimidine and azolopyrimidine systems based thereon, which exhibit a wide spectrum of biological activity due to structural similarity with nitrogenous bases, is of a special interest [2][3][4][5]. Interaction of non-fluorinated 2-ethoxymethylidene-3-oxo

C-5’-Triazolyl-2’-oxa-3’-aza-4’a-carbanucleosides: Synthesis and biological evaluation

• Roberto Romeo,
• Caterina Carnovale,
• Salvatore V. Giofrè,
• Maria A. Chiacchio,
• Adriana Garozzo,
• Emanuele Amata,
• Giovanni Romeo and
• Ugo Chiacchio

Beilstein J. Org. Chem. 2015, 11, 328–334, doi:10.3762/bjoc.11.38

• ][11][12]. Many structural variations of the natural nucleosides have been exploited. In general, the performed modifications included the replacement of the furanose moiety by other carbon or heterocyclic systems [13][14] or even acyclic fragments [15][16], the substitution of pyrimidine or purine

• –alkyne cycloadditions, no traces of 1,5-regioisomers were observed [47][48]. The structure of the obtained compounds was assessed according to 1H NMR, 13C NMR and MS data. In particular, the 1H NMR spectra of 5-methyl-1-[(3RS,5SR)-2-methyl-3-(1H-1,2,3-triazol-1-ylmethyl)isoxazolidin-5-yl]pyrimidine-2,4

• (1H,3H)diones 13 and 5-methyl-1-[(3RS,5RS)-2-methyl-3-(1H-1,2,3-triazol-1-ylmethyl)isoxazolidin-5-yl]pyrimidine-2,4(1H,3H)diones 14 show, besides the resonances of the protons of the isoxazolidine unit, diagnostic resonances at 7.25–7.75 ppm, as a singlet, for the proton of the triazole system, and at

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• , arylethylenes, and arylacetylenes were used as precursors of the acyloxy fragment. The cross-dehydrogenative C–O coupling with 2-arylpyridines 4 proceeds also in the presence of the Cu(OAc)2/O2 system [40] and under electrochemical oxidation in the presence of Pd(II) salts [41]. The pyrimidine (acetoxylation of

• arenes (Scheme 4). The pyridine, pyrimidine, or pyrazole moiety serves as the directing group in the oxidative ortho-alkoxylation of arenes 16 with the Cu(OAc)2/AgOTf/O2 system giving coupling products 17 (Scheme 5) [47]. It is supposed that copper is inserted into the C–H bond of arene, the resulting Cu

NAA-modified DNA oligonucleotides with zwitterionic backbones: stereoselective synthesis of A–T phosphoramidite building blocks

• Boris Schmidtgall,
• Claudia Höbartner and
• Christian Ducho

Beilstein J. Org. Chem. 2015, 11, 50–60, doi:10.3762/bjoc.11.8

• phosphoramidites with X representing pyrimidine or purine nucleobases appears to be feasible. This will enable the preparation of NAA-modified oligonucleotides with significant variations in the base sequence. We are currently finishing the synthesis of a comprehensive set of corresponding X–T phosphoramidites

The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

• Volodymyr V. Tkachenko,
• Elena A. Muravyova,
• Sergey M. Desenko,
• Oleg V. Shishkin,
• Svetlana V. Shishkina,
• Dmytro O. Sysoiev,
• Thomas J. J. Müller and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2014, 10, 3019–3030, doi:10.3762/bjoc.10.320

• azoloazine with high chemo- and regioselectivity [11][13][14][15]. In particular, three-component heterocyclizations involving 3-amino-1,2,4-triazoles or 4-substituted 5-aminopyrazoles yielded either 4,5,6,7-tetrahydroazolo[1,5-a]pyrimidine-6-carboxamides under ultrasonication at room temperature (kinetic

• control) or 4,7-dihydroazolo[1,5-a]pyrimidine-6-carboxamides at reflux in an applicable solvent (thermodynamic control), respectively (Scheme 1). The behavior of the reaction of 5-aminopyrazoles containing substituents in the position 3 is influenced by the structure of aminoazoles and aldehydes, giving

• ). Obtaining of two classes of compounds was found to originate from steric influence rendered by the alkyl moiety of the ester group in the active methylene species. Inspired by Světlik’s studies, Jing et al. [17] developed an efficient method for the synthesis of oxygen-bridged pyrimidine tricyclic

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• (Table 2) show that the phenanthridine/phenanthridinium cation interacts with purine ss-sequences with affinity approximately one–two orders of magnitude lower in comparison to ds-DNA or ds-RNA, while interaction with pyrimidine ss-polynucleotides is even one order of magnitude lower. This agrees well