Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• -headed nucleoside 6. The removal of the silyl protecting group with NEt3·3HF in THF yielded 2′-(N-benzoylcytosin-1-yl)methyl-arabinofuranosyl-N-benzoylcytosine (7, Scheme 2) [42]. The double-headed nucleoside 7 was dimethoxytritylated and phosphitylated following the standard procedure and incorporated

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• removal of the silyl protecting group, followed by a carboxylation and acylation gave 13. Koide’s group [13] reported a second-generation route to 13, which utilized the Corey–Bakshi–Shibata chiral oxazaborolidine catalyst 21 [20] for the asymmetric reduction of the THP-protected 5-hydroxy-3-pentyn-2-one

• . The removal of the silyl protecting group and hydrolysis of the methyl ester afforded the carboxylic acid 108. A subsequently attempted Suzuki–Miyaura coupling of 108 with vinyl boronates was described as “capricious”, and thus the acid was esterified with the tert-butyl donor reagent 109 to afford

• generate the mixed cyclic ketal 120. Finally, the removal of the C-4’ silyl protecting group, acylation of the resultant alcohol, removal of the C-4 silyl protecting group, and ketal hydrolysis generated FR901464 (1). Fragment coupling via olefin cross-metathesis Koide’s group was the first to demonstrate

Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy

• Daniela Imperio,
• Erika Del Grosso,
• Silvia Fallarini,
• Grazia Lombardi and
• Luigi Panza

Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135

• protecting group gave the intermediate 3 in good yield. Standard substitution of the hydroxy group gave the 1-deoxy-1-iododerivative 4. Base-promoted dehydroiodination, followed by Zémplen removal of the benzoate gave the desired enol ether 6, which was selected as precursor for the preparation of the first

• protected sugar precursors (Figure 3). The synthesis of the first analogue 8, shown in Scheme 1, started from known compound 1, that is easily obtained from 2,3,5-tri-O-benzyl-ᴅ-arabinose according to a literature procedure [15]. Benzoylation of the free hydroxy group of 1, followed by removal of the silyl

Synthesis of pyrrolidine-based hamamelitannin analogues as quorum sensing inhibitors in Staphylococcus aureus

• Jakob Bouton,
• Kristof Van Hecke,
• Reuven Rasooly and
• Serge Van Calenbergh

Beilstein J. Org. Chem. 2018, 14, 2822–2828, doi:10.3762/bjoc.14.260

• -propanediol (16), which was selectively monoprotected in high yield as TBS ether (Scheme 3) [25]. The remaining alcohol was then substituted for a phthalimide via Mitsunobu reaction. Phthalimide deprotection, acylation with benzoic acid, and removal of the silyl protecting group furnished 10. Fragments 9 and

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

• ) [74]. Protected D-ribonolactone 27 was treated with lithiated pyridine to obtain lactol 28 (Figure 10B). Deoxygenation and reduction gave 29, wherein the isopropylidene group was also removed. Conversion of the cyano to an amide group, followed by removal of the silyl protecting group gave 24, which

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• = 75:25). Further modifications (removal of the sulfinyl group and the silyl protecting group in acidic conditions, transformation of the amine in methyl carbamate and oxidation of the primary alcohol into the corresponding carboxylic acid) gave the final isostere 93. In 2013, Pannecoucke and co

• -workers proposed a new strategy based on a chemoenzymatic reduction of ethyl 2-oxocyclopentanecarboxylate (94) using Baker’s yeast to afford the corresponding chiral alcohol 95 (Scheme 19) [53]. Then, reduction of the ester into the primary alcohol, its selective protection by a silyl protecting group

A postsynthetically 2’-“clickable” uridine with arabino configuration and its application for fluorescent labeling and imaging of DNA

• Heidi-Kristin Walter,
• Bettina Olshausen,
• Ute Schepers and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2017, 13, 127–137, doi:10.3762/bjoc.13.16

• protecting group from nucleoside 5, the 5’-position of nucleoside 2 was again protected by 4,4’-dimethoxytrityl chloride (DMTr-Cl) and, finally, the 3’-position of nucleoside 6 was phosphitylated. Remarkably, the overall yield of phosphoramidite 7 with the optimized conditions over the described five steps

• functions of nucleoside 3 were selectively protected by the Markiewicz silyl ether [22]. The central step of the whole synthetic procedure was the alkylation of the 2’-OH function of nucleoside 4 by propargylic bromide which worked in 65% yield in the presence of NaH as base. After removal of the silyl

Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

• Serena Traboni,
• Emiliano Bedini and
• Alfonso Iadonisi

Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271

• experimentally simple tool for the straightforward access to saccharide building-blocks useful in organic synthesis. Keywords: carbohydrates; one-pot synthesis; regioselective protection; silyl protecting group; solvent-free reaction; Introduction The application of an orthogonal set of protecting groups

• after in situ peracetylation (Table 2, entry 8). The scope of the TBAB-catalyzed silyl protection under solvent-free conditions was next examined for the regioselective attachment of TBDPS (Table 2, entries 9–13), a commonly used silyl protecting group bulkier than TBDMS and more resistant to acidic

Synthesis of a deuterated probe for the confocal Raman microscopy imaging of squalenoyl nanomedicines

• Eric Buchy,
• Branko Vukosavljevic,
• Maike Windbergs,
• Dunja Sobot,
• Camille Dejean,
• Simona Mura,
• Patrick Couvreur and
• Didier Desmaële

Beilstein J. Org. Chem. 2016, 12, 1127–1135, doi:10.3762/bjoc.12.109

• directly the alcohol 28 in 41% yield through concomitant reduction of the intermediate allylic chloride and cleavage of the silyl protecting group. The reductive cleavage of tert-butyldiphenylsilyl ethers by LiAlH4 has been previously noticed [39]. Jones oxidation straightforwardly completed the synthesis

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

• Marco G. Rigamonti and
• Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

• , lippidulcine B (3b), after TBAF mediated cleavage of the silyl protecting group, was isolated in 73% yield and with an excellent de of 99% (by 1H NMR), ([α]D +123° (c 1.5, CHCl3) vs lit. [8] [α]D +113.3° (c 0.4, CHCl3)), confirming the absolute stereochemistry that it has been previously assigned. It is

Enantioselective synthesis of polyhydroxyindolizidinone and quinolizidinone derivatives from a common precursor

• Nemai Saha and
• Shital K. Chattopadhyay

Beilstein J. Org. Chem. 2014, 10, 3104–3110, doi:10.3762/bjoc.10.327

• . The O-benzylated compound 14, however, proved to be more useful in the subsequent synthetic sequence. Thus, HCl-mediated deprotection of the acetal unit in 14 resulted in simultaneous removal of the silyl protecting group leading to the triol derivative 16 in an impressive yield of 89%. One-pot

Galactan synthesis in a single step via oligomerization of monosaccharides

• Marius Dräger and
• Amit Basu

Beilstein J. Org. Chem. 2014, 10, 2658–2663, doi:10.3762/bjoc.10.279

• the reaction using donor 2, which lacks a silyl protecting group on the primary hydroxy group, proved to be remarkably clean, providing products ranging from the monosaccharide to the tetrasaccharide in isolable yield (Table 1, entry 4). In all of the reactions carried out thus far, we noticed that

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• desired DVCPR in almost quantitative yield at elevated temperature, followed by removal of the silyl-protecting group under acidic conditions to furnish cycloheptenone 70. Standard functional group interconversion furnished diolefin 71. Subjection of this compound to Heck coupling conditions resulted in

Efficient synthesis of phenylene-ethynylene rods and their use as rigid spacers in divalent inhibitors

• Francesca Pertici,
• Norbert Varga,
• Arnoud van Duijn,
• Matias Rey-Carrizo,
• Anna Bernardi and
• Roland J. Pieters

Beilstein J. Org. Chem. 2013, 9, 215–222, doi:10.3762/bjoc.9.25

• a methoxy group. The hydroxy version led to some migration of the silyl protecting group upon attempted monodeprotection, and alternative strategies had to be devised for the synthesis of the two-unit spacer. Compounds 17 and 19, containing four and five phenylene-ethynylene units, respectively, can

Synthesis and antifungal properties of papulacandin derivatives

• Marjolein van der Kaaden,
• Eefjan Breukink and
• Roland J. Pieters

Beilstein J. Org. Chem. 2012, 8, 732–737, doi:10.3762/bjoc.8.82

• 20, but in our hands a more complicated mixture resulted. We concluded that under our conditions deprotonation of the protecting group (protons α to silicon) may be competitive with the desired α-lithiation next to oxygen. Use of the more substituted TIPS silyl protecting group in 19 indeed solved

• , the cyclic silyl protecting group was first removed by using TBAHF in THF, followed by the deprotection of the TIPS group with TBAF and reintroduction of the cyclic silyl protecting group, giving 39. To circumvent this problem a silanol building block analogue of 22 bearing three TIPS protecting

Synthesis of fluorinated maltose derivatives for monitoring protein interaction by ¹⁹F NMR

• Michaela Braitsch,
• Hanspeter Kählig,
• Georg Kontaxis,
• Michael Fischer,
• Toshinari Kawada,
• Robert Konrat and
• Walther Schmid

Beilstein J. Org. Chem. 2012, 8, 448–455, doi:10.3762/bjoc.8.51

• with Pd/C [36], followed by a Zemplén saponification to obtain product 15. Starting from 4′,6′-O-benzylidene maltose 10 [37], the primary alcohol was protected as tert-butyldimethylsilyl ether followed by standard peracetylation (Scheme 2). Treatment of the silyl protecting group with an excess of

Synthesis of 6-PEtN-α-D-GalpNAc-(1–>6)-β-D-Galp-(1–>4)-β-D-GlcpNAc-(1–>3)-β-D-Galp-(1–>4)-β-D-Glcp, a Haemophilus influenzae lipopolysacharide structure, and biotin and protein conjugates thereof

• Andreas Sundgren,
• Martina Lahmann and
• Stefan Oscarson

Beilstein J. Org. Chem. 2010, 6, 704–708, doi:10.3762/bjoc.6.80

• -containing lactose derivative a suitably protected lacto-N-neotetraose tetrasaccharide structure was constructed through subsequential couplings with two thioglycoside donors, a glucosamine residue followed by a galactose derivative, using NIS/AgOTf as promoter. Removal of a silyl protecting group at the

Synthesis of the fluorescent amino acid rac-(7-hydroxycoumarin-4-yl)ethylglycine

• Manfred Braun and
• Torsten Dittrich

Beilstein J. Org. Chem. 2010, 6, No. 69, doi:10.3762/bjoc.6.69

• imine 7 in 67% yield. Under the aprotic conditions of the alkylation protocol, the silyl protecting group turned out to be stable, a fact which facilitated the purification of the imine 7. It is an obvious idea to apply the established protocols for the enantioselective alkylation of ester 6 under phase

Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules

• Matthias Lehmann and
• Jens Seltmann

Beilstein J. Org. Chem. 2009, 5, No. 73, doi:10.3762/bjoc.5.73

• iodobenzene 5 with ethynyl compound 4 and subsequent cleavage of the silyl protecting group afforded the arm derivatives 6. As in the previously published two-step synthesis, the arms 6 were linked successively to the non-symmetric thiadiazole bending unit 7 (Scheme 2) [24]. All compounds were carefully

Synthesis of chiral cyclohexanes and carbasugars by 6-exo-dig radical cyclisation reactions

• Rajeev K. Shrivastava,
• Elise Maudru,
• Gurdial Singh,
• Richard H. Wightman and
• Keith M. Morgan

Beilstein J. Org. Chem. 2008, 4, No. 43, doi:10.3762/bjoc.4.43

• diastereomeric mixture 2b was converted to the MOM ethers 4a and 4b that could be separated in a combined yield of 64% with an anti:syn ratio of 3.5:1. Both of these diastereoisomers were processed separately. Removal of the silyl protecting group of 4a and 4b gave the corresponding primary alcohols 8a and 8b in

The use of chiral lithium amides in the desymmetrisation of N-trialkylsilyl dimethyl sulfoximines

• Matthew J. McGrath and
• Carsten Bolm

Beilstein J. Org. Chem. 2007, 3, No. 33, doi:10.1186/1860-5397-3-33

• ] Results and Discussion N-Trialkylsilyl protected sulfoximines were chosen as candidates for chiral base desymmetrisation as simple variation of the silyl protecting group allows for tuning of the steric bulk at the sulfoximine nitrogen and because of the potential for subsequently unmasking the

Flexible synthetic routes to poison- frog alkaloids of the 5,8-disubstituted indolizidine- class I: synthesis of common lactam chiral building blocks and application to the synthesis of (-)-203A, (-)-205A, and (-)-219F

• Naoki Toyooka,
• Dejun Zhou,
• Hideo Nemoto,
• H. Martin Garraffo,
• Thomas F. Spande and
• John W. Daly

Beilstein J. Org. Chem. 2007, 3, No. 29, doi:10.1186/1860-5397-3-29

• indolizidines (-)-203A [22] and (-)-205A [23] from 1, and (-)-219F [2] from 2, respectively (Scheme 3, Scheme 4). Removal of the silyl protecting group in 1 was performed by treatment with TBAF to afford the corresponding alcohol 13, which was converted to the homologated ester 14 via a two-step oxidation