Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• previously reported methods required high temperatures [118][119][120]. A library of compounds was reported by that group using this approach, and a plausible mechanism is shown in Figure 13. Arylation of purines: Purine bases and purine nucleosides, which are common structural motifs in DNA and RNA, have an

An improved synthesis of adefovir and related analogues

• David J. Jones,
• Eileen M. O’Leary and
• Timothy P. O’Sullivan

Beilstein J. Org. Chem. 2019, 15, 801–810, doi:10.3762/bjoc.15.77

• the versatility of our approach. Keywords: acyclic nucleoside phosphonate; adefovir; alkylation; antiviral; N-alkylation; purine; Introduction The acyclic nucleoside phosphonate adefovir (1) [1], administered as its dipivoxil prodrug form (2) [2], is used clinically for the treatment of infections

• low to moderate yields as the reactions fail to reach completion or else furnish multiple side-products. The successful application of such iodide-based electrophiles is precedented, as demonstrated by the work of Ubasawa et al. in their preparation of purine analogue 17 from 15 (Scheme 3) [52]. A

• , constituting an attractive alternative to current literature methods for accessing 6. To explore the utility of iodide 14 in the synthesis of novel antivirals, we examined its reactivity towards other 6-substituted purine nucleobase analogues (Scheme 6). Alkylation of both 6-chloropurine (22) and N6

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• 5-HT3R antagonists are based on an aromatic system either connected to a purine/pyrimidine moiety via a thioether bridge or a quinoxaline moiety via an amide bond. Referring to this work performed by the groups of DiMauro [60] and Jensen [61], we envisioned that the replacement of the thioether or

• . Synthesis of the purine and thienopyrimidine-based derivatives Scheme 4 depicts the general procedure applied for the synthesis of differently substituted purine- and thienopyrimidine azobenzene derivatives. Differently substituted non-photochromic antagonists were chosen as lead structures delivering

• substitution at a chloro-substituted purine (15a,b) or thienopyrimidine (15c), respectively, and subsequent oxidation of the hydrazine moiety afforded the corresponding azobenzene derivatives 16a–d [71]. Synthesis of azobenzene-extended thiopurine derivatives To further tune the photochromism and compare the

Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• transformed into the title compounds by CuAAC reaction. The designed compounds belong to the push–pull systems and possess promising fluorescence properties with quantum yields in the range from 28% to 60% in acetonitrile solution. Due to electron-withdrawing properties of purine and 7-deazapurine

• ; Introduction Purine [1][2][3][4][5][6][7] and 7-deazapurine (IUPAC name: pyrrolo[2,3-d]pyrimidine) [8][9][10][11] derivatives have been progressively studied for decades due to their wide range of biological activities and photophysical properties. Currently, the synthesis of push–pull systems is a promising

• direction in the development of various fluorescent (7-deaza)purine derivatives [12][13][14][15][16]. The push–pull effect arises by adding electron-donating and electron-withdrawing groups at the opposite ends of π-conjugated systems. Large Stokes shifts and high quantum yields are usually characteristic

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• enzymatic synthesis of NR+ from α-D-ribose-1-phosphate and Nam by catalysis with purine nucleoside phosphorylase and sucrose phosphorylase is described in a US patent application by Velasquez et al. [46]. In the NMR experiments, the authors demonstrated the preparation of NR+ but did not isolate pure NR+. 3

• appropriate work-up procedures for NR+/NRH derivatives, as this class of nucleoside greatly differs from the canonical purine and pyrimidine nucleosides. For instance, the glycosyl bond of NR+ was shown to be very susceptible to cleavage in methanolic solutions of ammonia [39]. As such, to get the

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• pool; glutamate analogues; Introduction L-Glutamic acid (1, Figure 1) plays an important role in the biosynthesis of purine and pyrimidine nucleobases [1]. It also takes part in metabolic transformation to L-glutamine by L-glutamate synthetase (GS) which is crucial for cell maintenance. In neoplastic

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

• Sibylle Frei,
• Adam K. Katolik and
• Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

• 3’-adjacent nucleotide are thought to favourably contribute in both F-RNA and F-ANA duplexes [13]. Furthermore, in duplexes of the F-ANA with complementary RNA, internucleosidic C–H···F–C pseudohydrogen bonds are proposed at pyrimidine-purine steps to additionally stabilize the structure [14][15

Thermophilic phosphoribosyltransferases Thermus thermophilus HB27 in nucleotide synthesis

• Ilja V. Fateev,
• Ekaterina V. Sinitsina,
• Aiguzel U. Bikanasova,
• Maria A. Kostromina,
• Elena S. Tuzova,
• Larisa V. Esipova,
• Tatiana I. Muravyova,
• Alexei L. Kayushin,
• Irina D. Konstantinova and
• Roman S. Esipov

Beilstein J. Org. Chem. 2018, 14, 3098–3105, doi:10.3762/bjoc.14.289

• thermophilic transferases in nucleotide synthesis. A scheme of purine nucleotide synthesis using TthAPRT and TthHPRT is shown in Figure 2. Results and Discussion Genes TT_RS08985 and TT_RS06315 from T. thermophilus HB27, coding TthHPRT and TthAPRT, were cloned into expression plasmid vectors pET 23a+ and pET

• atoms. Probably, the presence of nitrogen atom at C7 position of purine heterocycles plays an important role in reactions catalyzed by phosphoribosyltransferase, and also affects the substrate properties of TthHPRT and TthAPRT. Two nucleotides were synthesized using TthHPRT or TthAPRT (see Figure 6

• towards different heterocyclic bases was carried out and temperature-dependence and magnesium chloride concentration-dependence of enzymes activity were determined. TthHPRT can be used for the synthesis of nucleotides containing different purine derivatives including 8-aza- and 8-aza-7-deazapurine. The

Nucleoside macrocycles formed by intramolecular click reaction: efficient cyclization of pyrimidine nucleosides decorated with 5'-azido residues and 5-octadiynyl side chains

• Jiang Liu,
• Peter Leonard,
• Sebastian L. Müller,
• Constantin Daniliuc and
• Frank Seela

Beilstein J. Org. Chem. 2018, 14, 2404–2410, doi:10.3762/bjoc.14.217

• . Monomeric purine and pyrimidine nucleosides form smaller ring systems known as cyclonucleosides incorporating O, N or S-bridges within the sugar moiety or between the nucleobase and the sugar residue [6]. Macrocycles can be obtained by a variety of chemical reactions [7][8][9][10]. Often, several protection

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• published a direct one-pot synthesis of exclusively β-configured nucleosides from unprotected or 5-O-monoprotected D-ribose using optimized Mitsunobu conditions with various purine- and pyrimidine-based heterocycles. Here, DBU was applied first, followed by DIAD and P(n-Bu)3 [106]. Two years later Seio and

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• iodine-mediated glycosylation to purine 4’-thionucleosides [46]. However, the reaction of 36 with 6-chloropurine resulted in the formation of a regioisomer reacting at the 4-position without any formation of the desired purine 4’-thionucleoside. The result should relate to the acidity of the α hydrogen

• 75 in 64% yield while suppressing the formation of 74 (Table 1, entry 5). Minakawa’s group attempted to apply the aforementioned reaction to the synthesis of purine derivatives [60]. Based on the reports by Jeong et al., who synthesized 4’-selenoadenosine using the Vorbrüggen reaction [53], they

• conceived that the hypervalent iodine-mediated reaction of “disarmed” sugar donor 73 bearing an electron-withdrawing group at the 2-position would not readily yield the desired purine derivative. Therefore, they decided to use “armed” seleno sugar 67 as a donor for the hypervalent iodine-mediated

Oligonucleotide analogues with cationic backbone linkages

• Melissa Meng and
• Christian Ducho

Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111

• the cleavage conditions used in the solid phase-supported synthesis of native DNA and also allowed the introduction not only of pyrimidine, but also of purine bases into the oligonucleotide analogue [53]. The method was based on the activation of the 5′-monomethoxytrityl (MMTr)-protected 3'-thiourea

• protecting group to yield the free 5'-amine 34. Subsequent iterative coupling–deprotection cycles resulted in the formation of the guanidinium-linked oligomer 35. After basic guanidine and purine deprotection and concomitant cleavage from the solid support, final acidic deprotection furnished A5T

• synthesis of purine-containing guanidinium-linked DNG oligomer 36 in the 3'→5' direction (MMTr = monomethoxytrityl). Bruice's synthesis of S-methylthiourea-linked DNmt oligomer 43. Retrosynthetic summary of Ducho's synthesis of partially zwitterionic NAA-modified oligonucleotides 48 (BOM = benzyloxymethyl

Synthesis of pyrazolopyrimidinones using a “one-pot” approach under microwave irradiation

• Mark Kelada,
• John M. D. Walsh,
• Robert W. Devine,
• Patrick McArdle and
• John C. Stephens

Beilstein J. Org. Chem. 2018, 14, 1222–1228, doi:10.3762/bjoc.14.104

• compounds, as well as its structural similarity to purine [1][2][3][4]. Pyrazolo[1,5-a]pyrimidinone derivatives have found use in the battle against several illnesses including cancer [5], viral infections [6][7][8], obesity [9], and cystic fibrosis [10] (Figure 1). It is these pharmacological properties

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• absence of any observable intramolecular cyclisation of the unprotected purine nucleoside derivatives typical of solution-phase reactions using such substrates. More variable yields were obtained using potassium selenocyanate which required grinding in the presence of DMF to promote the reaction with

• latter reaction rapidly decomposed during work-up in solution. Regioselective and stereoselective glycosidation of adenine, N6-benzoyladenine, N4-benzoylcytosine, thymine and uracil to the corresponding β-N9-purine or β-N1-pyrimidine ribosides was achieved on gram scales under Vorbrüggen-type conditions

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• , synthetic C-nucleosides, such as immucillin-H and GS-5734, have shown potent activity against purine nucleoside phosphorylases (PNP) and broad spectrum antiviral activities. Synthetic approaches to C-nucleosides. A. Two common strategies for C-nucleoside synthesis involve functionalization at C1' and

AuBr₃-catalyzed azidation of per-O-acetylated and per-O-benzoylated sugars

• Jayashree Rajput,
• Srinivas Hotha and
• Madhuri Vangala

Beilstein J. Org. Chem. 2018, 14, 682–687, doi:10.3762/bjoc.14.56

• purine and pyrimidine nucleoside synthesis using per-O-acyl/per-O-benzoyl furanosyl and pyranosyl o-hexynylbenzoates [23]. Subsequently, Hotha and co-workers utilized propargyl 1,2-orthoesters and alkynyl glycosyl carbonate donors for the synthesis of pyrimidine nucleosides [24][25]. In addition, N

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• , mutagenous properties were also shown. Freccero et al. examined the photogeneration by laser flash photolysis and reactivity of naphthoquinone methides as well as their activity as purine selective DNA alkylating agents [93]. Farrell et al. studied the mechanism of the cytotoxic action of naphthoquinone

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• are currently used in several marketed drugs like cartazolate (1), zaleplon (2), sildenafil (3), allopurinol (4), indiplon (5), etazolate (6) etc. (Figure 1). Fused pyrazole derivatives, especially pyrazoloazines have been reported to mimic purine bases, present in DNA and RNA, due to close structural

Synthetic mRNA capping

• Fabian Muttach,
• Nils Muthmann and
• Andrea Rentmeister

Beilstein J. Org. Chem. 2017, 13, 2819–2832, doi:10.3762/bjoc.13.274

• hydrolytically less stable than other purine nucleosides. Under basic conditions which are commonly used for RNA deprotection and cleavage from the solid support, opening of the imidazole ring of the 7-methylguanine would occur [111]. Thus, for synthesis of the cap structure on the solid support, standard

Metal-mediated base pairs in parallel-stranded DNA

• Jens Müller

Beilstein J. Org. Chem. 2017, 13, 2671–2681, doi:10.3762/bjoc.13.265

• in the context of this review is the pyrimidine:purine:pyrimidine triplex, where each base triple formally comprises a regular Watson–Crick base pair and an additional pyrimidine residue hydrogen-bonded to the central purine moiety via its Hoogsteen edge. Conceptually, this Hoogsteen-bonded part of

• glycosidic bond conformations [46]. It needs to be noted that these correlations are derived from base pairs and triples comprising canonical purine and pyrimidine nucleobases only. In particular, it is assumed that both Hoogsteen and reversed Hoogsteen pairing involve the Hoogsteen edge of one purine

• residue and the Watson–Crick edge of the complementary pyrimidine or purine moiety. Artificial base pairs involving two purine entities facing each other via their respective Hoogsteen edge (vide infra, Scheme 8b) need to be treated differently, as this additional structural change leads to a change from

¹⁵N-Labelling and structure determination of adamantylated azolo-azines in solution

• Sergey L. Deev,
• Alexander S. Paramonov,
• Tatyana S. Shestakova,
• Igor A. Khalymbadzha,
• Oleg N. Chupakhin,
• Julia O. Subbotina,
• Oleg S. Eltsov,
• Pavel A. Slepukhin,
• Vladimir L. Rusinov,
• Alexander S. Arseniev and
• Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

• -azine core with a bridgehead nitrogen atom is found in many natural products [5][6] and biologically active synthetic compounds [7][8]. The purine-like scaffold of these nitrogen-containing heterocycles is frequently used in medicinal chemistry and drug design. For example, 6-nitro-1,2,4-triazolo[5,1-c

• product structure were also found for N-arylation or N-alkylation with tert-butyl fragments in the series of 1,2,3-triazole [15][16], tetrazole [17][18][19][20], and purine [21] derivatives. Meanwhile, knowledge of the accurate chemical structures of N-substituted heterocycles is essential for biomedical

Synthesis of oligonucleotides on a soluble support

• Harri Lönnberg

Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134

• applied to the synthesis of a PEG-conjugated 12-mer antisense ODN [53] and a 13-mer purine-rich triple-helix forming sequence [54]. Immobilization of the 3´-terminal nucleosides via a succinyl linker was, however, replaced by direct phosphoramidite coupling to the terminal OH of PEG, which gave a stable

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123