A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• diversification and applications in medicinal chemistry. They will also be useful for nucleosidation reactions to prepare the corresponding nucleosides in straightforward manner. Experimental General. Chemical reagents and solvents were purchased in the highest available quality from commercial suppliers (Merck

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

• addition of an electrophilic iodine during the nucleosidation step followed by reduction. The gem-difluorinated bicyclic nucleoside was then converted into the corresponding phosphoramidite building block which was incorporated into oligonucleotides. Thermal denaturation experiments of these

• into the bicyclic derivative 6 could be ruled out (Table 1, entry 3). Consequently, the bicyclic derivative 6 was thought to have its origin in the NIS-mediated nucleosidation step. In analyzing the crude reaction product in more detail, apart from the iodinated nucleosides 2α/β, the presence of an

• ]. Optimisation of the nucleosidation conditions to an increased amount of NIS (2 equiv) and prolongation of the reaction time in combination with the adjustment of the Bu3SnH amount to 3 equivalents led to higher yields of the bicyclic nucleoside 6 (Table 1, entry 5). An additional proof for the reaction

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• either by a NIS-mediated or Vorbrüggen nucleosidation yielded in both cases the β-tricyclic nucleoside as major anomer. Subsequent desilylation and cyclopropane ring opening of these tricyclic intermediates afforded the unsaturated 6’F-bc4,3 nucleosides. The successful incorporation of the corresponding

• a standard glycosyl donor for nucleoside synthesis. The nucleosidation was carried out by applying classical Vorbrüggen conditions [57] on the sugars 11α/β, yielding the β-nucleoside 12β as major anomer. The α/β-ratio of 1:1.5 was acceptable and the configuration at the C(1’) was assigned by 1H,1H

Facile synthesis of a 3-deazaadenosine phosphoramidite for RNA solid-phase synthesis

• Elisabeth Mairhofer,
• Elisabeth Fuchs and
• Ronald Micura

Beilstein J. Org. Chem. 2016, 12, 2556–2562, doi:10.3762/bjoc.12.250

• modern RNA research, in particular for atomic mutagenesis experiments to explore mechanistic aspects of ribozyme catalysis. Here, we report the 5-step synthesis of a c3A phosphoramidite from cost-affordable starting materials. The key reaction is a silyl-Hilbert–Johnson nucleosidation using unprotected 6

• -amino-3-deazapurine and benzoyl-protected 1-O-acetylribose. The novel path is superior to previously described syntheses in terms of efficacy and ease of laboratory handling. Keywords: deazapurine nucleoside; nucleosidation; protection groups; ribozymes; Introduction The synthesis of 3-deazaadenosine

• . Because of this frustrating situation, we set out to develop an efficient and easy-to-handle synthesis of a 3-deazaadenosine phosphoramidite building block. Results and Discussion Previously described synthetic routes to c3A via nucleosidation In 1966, Rousseau, Townsend, and Robins reported the

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

• –Jones nucleosidation using silylated thymine and TBAF [42][43][44], was converted into the corresponding iodo-derivative 10 by sequential tosylation and iodination. The subsequent reaction of 10 with sodium azide, performed at 50 °C in CH3CN/H2O (1:10) in the presence of NH4Cl for 48 h afforded two

Synthesis of phosphoramidites of isoGNA, an isomer of glycerol nucleic acid

• Keunsoo Kim,
• Venkateshwarlu Punna,
• Phaneendrasai Karri and
• Ramanarayanan Krishnamurthy

Beilstein J. Org. Chem. 2014, 10, 2131–2138, doi:10.3762/bjoc.10.220

• -chloroadenine has been utilized to overcome the solubility and regioselectivity (N7 versus N9 nucleosidation) issues. Yet, the conversion of the chloro to the NH2 group is not efficient enough to consider this option an attractive one [27]. The second option was the N6,N6-dibenzoyladenine derivative, but this

Structure/affinity studies in the bicyclo-DNA series: Synthesis and properties of oligonucleotides containing bc^en-T and iso-tricyclo-T nucleosides

• Branislav Dugovic,
• Michael Wagner and
• Christian J. Leumann

Beilstein J. Org. Chem. 2014, 10, 1840–1847, doi:10.3762/bjoc.10.194

• protect the secondary hydroxy group as TBS ether (→ 3). Indeed cyclopropanation of 3 with diethylzinc and CH2I2 proceeded stereospecifically, again from the convex side of the bicyclic system, to give 4. Subsequent nucleosidation of 4 via the Vorbrüggen procedure [31][32] with transient protection of the

• group in a bicyclic sugar scaffold that is otherwise very similar in flexibility and geometry. The corresponding building block 13 (Scheme 2) was easily available via nucleosidation of sugar intermediate 2 (in situ TMS protection of both hydroxy groups) leading to the mixture of anomeric nucleosides 11α

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• nucleosidation (Scheme 32) [86]. In this procedure an O-silylated pyrimidone (3.9) is combined with the acylated or benzoylated ribose derivative 3.10 in the presence of a strong Lewis acid. The generation of the reactive oxycarbenium ion as well as the liberated nucleophilic pyrimidone therefore occurs in situ