Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

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

• in a high yield and enantioselectivity (Scheme 5) [17][18]. The Rubottom oxidation [28] of 43 gave a separable mixture of the desired 44 and its C-14 epimer (≈7:1 ratio). The reductive deoxygenation of 44 proceeded via the tosylhydrazone to afford 45, which upon desilylation and alkyne isomerization

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• (III)–P(V) redox cycle, such as in catalytic Wittig-, aza-Wittig-, Staudinger-, Appel- and other reactions [16][17][18][19][20][21]. The ring strain of the four- and five-membered derivatives makes them highly susceptible to deoxygenation, thus they are ideal organocatalysts in P(III)–P(V) redox

Synthetic terpenoids in the world of fragrances: Iso E Super^® is the showcase

• Alexey Stepanyuk and
• Andreas Kirschning

Beilstein J. Org. Chem. 2019, 15, 2590–2602, doi:10.3762/bjoc.15.252

• transformed into cyclohexene 48 with shifted olefinic group by means of a reductive variant of the Wolff–Kishner deoxygenation. A straightforward four-step sequence finally yielded Iso E Super Plus® ((+)-34). Industrially pursued syntheses do not involve a specific stereoinducing step. In fact, it is

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• ring opening at the less substituted carbon and effective deoxygenation performed at the C2 substituent [39]. This strategy was applied in the formal synthesis of (R,R)-formoterol (14) and (R)-tamsulosin (15) (Scheme 5) which have been used as therapeutic drugs for many years [40][41]. They are

• NaBH4/ZnCl2 mixture (chelation controlled) gave the aziridine alcohol 20 as a major product. Reductive opening of the aziridine ring produced the amino alcohol 21 which was transformed into the substituted oxazolidin-2-one 22. Its catalytic hydrogenation effected deoxygenation at the benzylic position

• was subjected to a three-step deoxygenation (reduction, mesylation of the alcohol (2S,1'R)-78 and reduction of the mesylate) to locate the 2-phenylethyl substituent at C2. Installation of the pyrrolidine ring at C3 was achieved after opening of the aziridine ring with iodotrimethylsilane to give a

Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Katarzyna Urbaniak,
• Marcin Jasiński,
• Vladyslav Bakhonsky,
• Peter R. Schreiner and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43

• temperature [14]. An important reaction of 1 is the O-alkylation leading to alkoxyimidazolium salts, which display in some cases properties of ‘room temperature ionic liquids’ [15][16]. Finally, straightforward deoxygenation by treatment with Raney-Ni is also worth mentioning [17]. Condensations presented in

• completed after 2 h, and the main product isolated in 39% yield was the expected 1-(adamantyloxy)imidazole 8a (Scheme 4). In the product, the diagnostic HC(2) signal in the 1H NMR spectrum shifts high-field and appears at 7.34 ppm. Analogously, deoxygenation of N-oxides 7b–d led to the required imidazoles

• with N-(adamantyloxy)formaldimine, and 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides were obtained in high yields. In general, they react similarly to their 1-alkyl analogues and undergo deoxygenation without removal of the adamantyloxy fragment. The sulfur transfer reactions provide access to the

Synthesis of 1,4-imino-L-lyxitols modified at C-5 and their evaluation as inhibitors of GH38 α-mannosidases

• Maroš Bella,
• Sergej Šesták,
• Ján Moncoľ,
• Miroslav Koóš and
• Monika Poláková

Beilstein J. Org. Chem. 2018, 14, 2156–2162, doi:10.3762/bjoc.14.189

• study for (4-halo)benzylpyrrolidines 1 with retained primary hydroxymethyl function [30]. In both series of pyrrolidines 1 and 2, the presence of a halogen substituent at the aromatic unit slightly improved efficiency of the GMIIb inhibition. However, the deoxygenation of the hydroxymethyl function to a

Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles

• Dennis Hiltrop,
• Steffen Cychy,
• Karina Elumeeva,
• Wolfgang Schuhmann and
• Martin Muhler

Beilstein J. Org. Chem. 2018, 14, 1428–1435, doi:10.3762/bjoc.14.120

• ] reported on the beneficial role of increased surface polarity of carbon nanofibers introduced by oxygen groups in the deoxygenation of stearic acid over Pd NPs deposited in addition on this support. They identified a favorable mode of adsorption of the stearic acid via the carboxylic group for high support

• polarity instead of a flat adsorption mode for low support polarity [40]. The upright adsorption mode facilitates the deoxygenation due to the close contact with the Pd NPs pointing to the importance of metal-support interactions [40]. A similar adsorption-induced effect may be present in glycerol

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols

• Anna Czarnecka,
• Emilia Kowalska,
• Agnieszka Bodzioch,
• Joanna Skalik,
• Marek Koprowski,
• Krzysztof Owsianik and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105

• Structural and Material Research, Institute of Chemistry, Environmental Protection and Biotechnology, Faculty of Mathematics and Natural Sciences, Jan Długosz University in Częstochowa, Armii Krajowej 13/15, 42-200 Częstochowa, Poland 10.3762/bjoc.14.105 Abstract We present a successful deoxygenation

• patent literature [44]. Benzophenones were also reduced to diarylmethanes using supercritical iPrOH at 350 °C [1], BF3·OEt2/H2O [33] and PhSiH3/MoCl2O2(H2O)2 [45]. The reductive deoxygenation reactions of diarylmethanols proceed via carbocationic species, which are formed by protonation or complexation

• such diarylmethanols [60], as well as Cl, Br, C(O)OMe, MeO, MeS and NO2 groups in aromatic aldehydes and ketones, being reduced to methyl and methylene groups, respectively [27], are tolerated by this reagent system. The use of other procedures for deoxygenation of alcohols 5d, 6a and 6b with metal

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

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

• ][75][78]. Ribonolactone typically with its hydroxy groups protected, is amenable to nucleophilic substitutions [78][79]. Use of C-nucleophiles such as lithiated (hetero)aryls leads to C-C bond via a lactol intermediate (Figure 6A). Subsequent deoxygenation of the C1'–OH by Lewis acids (e.g., BF3·OEt2

• -dideazaadenine to obtain the lactol intermediate (Figure 7A) [63][65][69][70]. Deoxygenation of the lactol intermediate by BF3·OEt2 resulted in the oxocarbenium ion, which was then reduced using triethylsilane to obtain 2. Replacing triethylsilane with allyl trimethylsilane and trimethylsilyl cyanide gave C1

• ) [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

Electrochemical Corey–Winter reaction. Reduction of thiocarbonates in aqueous methanol media and application to the synthesis of a naturally occurring α-pyrone

• Ernesto Emmanuel López-López,
• José Alvano Pérez-Bautista,
• Fernando Sartillo-Piscil and
• Bernardo A. Frontana-Uribe

Beilstein J. Org. Chem. 2018, 14, 547–552, doi:10.3762/bjoc.14.41

• beneficial effect of β-oxygen substituents in radical deoxygenation [37], is dramatically favoured when the radical precursor group (or atom) is oriented antiperiplanar to the C−O bond via orbital interaction between the SOMO with the C−O σ* orbital [35]. Therefore, stabilization of intermediate E, which is

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• . Diketone 30 was prepared in a straightforward manner by C-C-coupling of nitrosoalkene NSA7 (generated in situ from the corresponding α-bromooxime 31) with silyl enolate of 2-methylcyclopentanone, and subsequent deoxygenation of the resulting oxime 32 with CAN. Unfortunately, attempts to convert pentalenone

• corresponding adduct 44 in 93% yield. Importantly, both stereoisomers obtained were oxime E,Z-isomers with the C-7 relative configuration being the same as in myrioneurinol. Subsequent deoxygenation and reduction of aldoxime followed by transformation of the malonate unit to the formyl group furnished

The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• product 89a. Though this reaction is cis-selective, cunningly, deoxygenation ultimately leads to the trans-THF fragment 90. The other THF subunit 93 of the natural product 87 was prepared via an oxidative mono-cyclization of triene 91. Thus, the desired cis-product 92a was obtained in 51% yield together

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

• C16 of 53. Whether the pyran-ring closure is also mediated by an enzymatic activity or if this reaction is a spontaneous process could not be clarified yet and may be subject for in vitro studies with the purified enzymes. The net-deoxygenation on C8 of pseudomonic acid B (57) is obtained by a

Stimuli-responsive HBPS-g-PDMAEMA and its application as nanocarrier in loading hydrophobic molecules

• Yongsheng Chen,
• Li Wang,
• Haojie Yu,
• Zain-Ul-Abdin,
• Ruoli Sun,
• Guanghui Jing,
• Rongbai Tong and
• Zheng Deng

Beilstein J. Org. Chem. 2016, 12, 939–949, doi:10.3762/bjoc.12.92

• -PDMAEMA [26] The synthetic routes to HBPS and HBPS-g-PDMAEMA are shown in Figure 1A. The synthesis of HBPS was done by using a Schlenk line system under argon atmosphere. The solution of monomer was prepared by the addition of 3.0 mL VBC (21.1 mmol) in 8.4 mL benzyl chloride followed by deoxygenation by

Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst

• Redouane Beniazza,
• Natalia Bayo,
• Florian Molton,
• Carole Duboc,
• Stéphane Massip,
• Nathan McClenaghan,
• Dominique Lastécouères and
• Jean-Marc Vincent

Beilstein J. Org. Chem. 2015, 11, 1950–1959, doi:10.3762/bjoc.11.211

• . Combining 1 with light, thus prevents the use of sodium ascorbate as reducing agent while a copper(II) complex is employed as precatalyst. The reactions were conducted not only under ascorbate-free conditions, but also under dioxygen-free conditions, deoxygenation being conveniently performed by Ar or N2

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• followed by deoxygenation which finally gave the paracyclophane 108 (85%, Scheme 15). Pinacol coupling: Kanomata and co-workers [123] have reported the synthesis of the cyclophane 112 by using pinacol coupling [124] mediated by SmI2. A double Sonogashira reaction of 1,4-diiodobenzene (109) with 4-pentyn-1

Attempts to prepare an all-carbon indigoid system

• Şeref Yildizhan,
• Henning Hopf and
• Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 363–372, doi:10.3762/bjoc.11.42

• ). To rationalize its formation we propose that the deoxygenation of 13 does indeed take place, but provides a carbenoid intermediate 15 rather than the vicinal diol complex that is usually postulated to be formed during the McMurry dimerization. Possibly the dimerization of the substrate molecule

Synthesis of dinucleoside acylphosphonites by phosphonodiamidite chemistry and investigation of phosphorus epimerization

• William H. Hersh

Beilstein J. Org. Chem. 2015, 11, 184–191, doi:10.3762/bjoc.11.19

• acylphosphonite would require different nucleoside moieties. One example can be found in the literature of a non-Arbuzov route leading to the dinucleoside analog of 3 where as reported by Hata et al., 3a [41] gives 3b via sequential coupling [42][43] (Scheme 1). While the deoxygenation of phosphine oxides is

• known [44][45], deoxygenation of the functionally much more complex phosphonate 3b to the dinucleoside analog of 1 was not attempted. Only one example of an acylphosphonite analog of 1 was found in the literature, namely, a dinucleoside formate reported by Caruthers et al. [46]. As shown in Scheme 1

Visible light photoredox-catalyzed deoxygenation of alcohols

• Daniel Rackl,
• Viktor Kais,
• Peter Kreitmeier and
• Oliver Reiser

Beilstein J. Org. Chem. 2014, 10, 2157–2165, doi:10.3762/bjoc.10.223

• developed is limited to benzylic, α-carbonyl, and α-cyanoalcohols; with other alcohols a slow partial C–F bond reduction in the 3,5-bis(trifluoromethyl)benzoate moiety occurs. Keywords: C–O bond activation; deoxygenation; photochemistry; photoredox catalysis; visible light; Introduction The dwindling

• established oil-based protocols developed in the chemical industry during the last century. A classical radical deoxygenation reaction using over-stoichiometric amounts of highly noxious chemicals [2] is the Barton–McCombie reaction, although nowadays several improved protocols are available [3]. Radical

• byproducts. Related to this work, Stephenson et al. elegantly succeeded in the direct deoxygenation of alcohols by their in situ conversion to iodides using triphenylphospine and iodine followed by visible light-mediated reduction with amines as stoichiometric sacrificial electron donor and fac-Ir(ppy)3 (ppy

Concise total synthesis of two marine natural nucleosides: trachycladines A and B

• Haixin Ding,
• Wei Li,
• Zhizhong Ruan,
• Ruchun Yang,
• Zhijie Mao,
• Qiang Xiao and
• Jun Wu

Beilstein J. Org. Chem. 2014, 10, 1681–1685, doi:10.3762/bjoc.10.176

• valopicitabine (NM-283) [21][22] and related nucleosides, there are suitable methodologies for the synthesis of carbohydrate 5 [23]. After the selective deoxygenation of the C-5′ hydroxy group of nucleosides 3, trachycladine A and B could be afforded. According to the preliminary results from our lab

• (unpublished results), the deoxygenation procedure of the C-5′ hydroxy group was accompanied by several undesired side reactions. Then we turned to synthetic route (B), which utilizes carbohydrate 4 as a Vorbrüggen glycosylation donor. Firstly, without the deoxygenation of the C-5′ hydroxy group at the late

Efficient routes toward the synthesis of the D-rhamno-trisaccharide related to the A-band polysaccharide of Pseudomonas aeruginosa

• Aritra Chaudhury,
• Sajal K. Maity and
• Rina Ghosh

Beilstein J. Org. Chem. 2014, 10, 1488–1494, doi:10.3762/bjoc.10.153

• the A-band polysaccharide of Pseudomonas aeruginosa. One of the key steps involved 6-O-deoxygenation of either partially or fully acylated 4,6-O-benzylidene-1-thiomannopyranoside by radical-mediated redox rearrangement in high yields and regioselectivity. The D-rhamno-thioglycosides so obtained

• allowed efficient access to the trisaccharide target via stepwise glycosylation as well as a one-pot glycosylation protocol. In a different approach, a 4,6-O-benzylidene D-manno-trisaccharide derivative was synthesized, which upon global 6-O-deoxygenation followed by deprotection generated the target D

• -rhamno-trisaccharide. The application of the reported regioselective radical-mediated deoxygenation on 4,6-O-benzylidene D-manno thioglycoside (hitherto unexplored) has potential for ramification in the field of synthesis of oligosaccharides based on 6-deoxy hexoses. Keywords: A-band polysaccharide; D

Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative

• Bernd Schmidt and
• Sylvia Hauke

Beilstein J. Org. Chem. 2014, 10, 1023–1031, doi:10.3762/bjoc.10.102

• and subsequent hydrogenation and reductive 6-deoxygenation [21][22]. Successful de novo approaches [14] to both enantiomers of amicetose include an Achmatowicz rearrangement–hydrogenation sequence, starting from enantiomerically pure 2-(1-hydroxyethyl)furan [23][24][25], a sequence comprising

Structure elucidation of female-specific volatiles released by the parasitoid wasp Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

• Armin Tröger,
• Teris A. van Beek,
• Martinus E. Huigens,
• Isabel M. M. S. Silva,
• Maarten A. Posthumus and
• Wittko Francke

Beilstein J. Org. Chem. 2014, 10, 767–773, doi:10.3762/bjoc.10.72

• with malonate and another methylmalonate (including deoxygenation steps) seemed to be plausible [16]. These biogenetic considerations excluded methyl groups at positions 9 and 11. To prepare a mixture of all stereoisomers of 14, we again used 2 as the starting material (Figure 2). Monobenzylation to 9

• corresponding deoxygenation steps) would produce the carbon skeleton of a 4,6,8,10-tetramethyltrideca-2,4-diene (15). Thus, from a biosynthetic point of view, the structure would be reasonable and follow established principles. To test the validity of our assumption, we transformed 13 into 15 by Wittig reaction

Asymmetric total synthesis of a putative sex pheromone component from the parasitoid wasp Trichogramma turkestanica

• Danny Geerdink,
• Jeffrey Buter,
• Teris A. van Beek and
• Adriaan J. Minnaard

Beilstein J. Org. Chem. 2014, 10, 761–766, doi:10.3762/bjoc.10.71

• 10 over two steps [23]. As an alternative deoxygenation procedure, we relied on the so-called Mozingo reduction. Although the procedure for dithiane formation has been reported to be catalytic in Lewis acid, we found a linear correlation between the amount of BF3·Et2O used and the conversion (Scheme

• components of Trichogramma turkestanica. Application of the iterative conjugate addition protocol for the preparation of 8. Deoxygenation and desilylation of 8. Vinylogous Horner–Wadsworth–Emmons olefination. Synthesis of α,β-unsaturated ester 15 using a Wittig reaction. Completion of the synthesis of the