Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• yields (89–94%) and mild reaction conditions [53]. In a related approach, in 2015, Mohanakrishnan and his group reported the synthesis of anthracene derivatives and other annulated products via the regioselective cyclization of asymmetric 1,2-diarylmethine diol 83b by using a HBr/AcOH system (Scheme 20

• converted to the substituted anthracenes 109 and 110 by varying the acidic workup procedures. In addition, they prepared 9-chloro-10-phenylanthracene (112) in good yield (87%) through diol 111 [59]. Synthesis of substituted benzo[a]anthracene and dibenzoanthracene derivatives Metal-catalyzed C–H bond

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• resulting 2,3-diol as acceptor in the following glycosylation [131]. A regioselective glycosylation strategy was developed to obtain a collection of linear glucans (8mer to 16mer) (Scheme 4), as well as a branched 9mer and 17mer [137][138]. A similar strategy based on the regioselective glycosylation of a

• 2,3-diol 4,6-O-benzylidene acceptor permitted to access various β(1–3)-glucans, ranging from trimer to 13mer [126]. Regioselectivity was also achieved using a gold-catalyzed glycosylation, to give a linear β(1–3)-linked 11mer and a branched 14mer in a convergent manner [139]. Collection of linear as

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• [158]. The synthesis started with a cyclopentene derivative, obtained after two steps from a diol via tosylation/displacement strategy with Me2CuLi·LiI. Then, after a Lewis acid-promoted cycloaddition, the alkylation of the α-carbon atom followed by regioselective Baeyer–Villiger oxidation provided the

Natural products in the predatory defence of the filamentous fungal pathogen Aspergillus fumigatus

• Jana M. Boysen,
• Nauman Saeed and
• Falk Hillmann

Beilstein J. Org. Chem. 2021, 17, 1814–1827, doi:10.3762/bjoc.17.124

• more likely to survive internalization by lung epithelial cells [147][154][155]. Although DHN-melanin is generally associated with immune evasion it was recently found to be recognized in higher animals via the C-type lectin receptor (MelLec) which interacts with the naphthalene-diol domain of DHN

Cascade intramolecular Prins/Friedel–Crafts cyclization for the synthesis of 4-aryltetralin-2-ols and 5-aryltetrahydro-5H-benzo[7]annulen-7-ols

• Jie Zheng,
• Shuyu Meng and
• Quanrui Wang

Beilstein J. Org. Chem. 2021, 17, 1481–1489, doi:10.3762/bjoc.17.104

• alkynyl-Prins cyclization, Friedel–Crafts alkenylation, and dehydration/aromatization reaction between 1-aryl-3-hexyne-2,6-diol derivatives and aldehydes, that led to the formation of 1,4-dihydro-2H-benzo[f]isochromenes [16]. The Prins reaction-induced cyclization, inter alia, became a versatile tool for

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• 1995, was previously identified as a polyamine with C2 symmetry and a 1,3-syn-diol moiety on a C10 carbon backbone – one of very few substituted polyamines to be isolated from nature. Its absolute configuration was later established by our first reported total synthesis in 2010. Herein we report the

• -pavettamine rather than pavettamine. Chain extension and stereoselective ketone reduction were achieved using the (R)-methyl p-tolyl sulfoxide chiral auxiliary to give the desired 1,3-syn-diol C5 unit. A protecting-group strategy was also developed for the orthogonal protection of the alcohol and amine

• yield. The first step involved esterification of malic acid using methanol, followed by selective reduction of the resulting dimethyl ester using borane dimethyl sulfide (BMS) yielding diol 5 (Scheme 2) [1][14][15]. The step achieved chemo-differentiation of the carboxyl groups present in 3 whilst

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 nucleosides 151a–d starting from LNA uridine diol 147 which in turn was synthesized from diacetone-α-ᴅ-allose following a procedure reported in the literature [76]. LNA uridine diol 147 was reacted with iodine and ceric ammonium nitrate (CAN) in acetic acid to afford the nucleoside 148. Nucleoside

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

• trimethylsilyl cyanide (TMSCN) in THF at −10 °C. The reaction product 142 was obtained in quantitative yield and good diastereomeric ratio. Further hydrolysis of the cyclic acetal, and subsequent epoxidation of the resulting diol under typical Mitsunobu conditions led to epoxide derivative 143. The piperidine

Synthesis of multiply fluorinated N-acetyl-D-glucosamine and D-galactosamine analogs via the corresponding deoxyfluorinated glucosazide and galactosazide phenyl thioglycosides

• Vojtěch Hamala,
• Lucie Červenková Šťastná,
• Martin Kurfiřt,
• Petra Cuřínová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2021, 17, 1086–1095, doi:10.3762/bjoc.17.85

• thioglycosides 27–31 (Scheme 3). As the 3,4-difluorinated thiogalactoside could not be accessed from compound 13 by reaction with PhSTMS/ZnI2 (Scheme 2), it was necessary to obtain 3,4-difluoro and 3,4,6-trifluoro analogs of GalNAc from 3-fluoro-4,6-diol 18. According to precedents in the literature [53

• ], deoxyfluorination of the C4-hydroxy group in compound 18 was expected to occur with inversion of configuration to give the desired galacto-configured 4-fluoro products. Accordingly, treatment of diol 18 with DAST resulted in deoxyfluorination of both hydroxy groups to yield trifluoro thiogalactosazide 34 (Scheme 3

• ). 4,6-O-Benzylidenation of diol 18 followed by regioselective opening of the benzylidene acetal produced compound 35. Subsequent DAST deoxyfluorination delivered the desired thioglycoside 36 (Scheme 3). For both compounds 18 and 35, deoxyfluorination of the C4 hydroxy group occurred with inversion of

Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

• Ákos Bajtel,
• Mounir Raji,
• Matti Haukka,
• Ferenc Fülöp and
• Zsolt Szakonyi

Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80

• -amino-1,3-diols, which underwent a regioselective ring closure with formaldehyde or benzaldehyde delivering pinane-condensed oxazolidines. During the preparation of 2-phenyliminooxazolidine, an interesting ring–ring tautomerism was observed in CDCl3. Keywords: 2-amino-1,2-diol; monoterpene; oxazolidin

• -2-one; stereoselective; tautomerism; Introduction The best known 2-amino-1,3-diol derivative sphingosine (1) plays a crucial role in intracellular signaling as second messenger, and its derivatives called sphingolipids are also critical for cell growth, cell differentiation, cell recognition, and

• the lack of a readily available natural sources and the high biological importance of sphingolipid analogues, their synthesis has been the subject of numerous studies [16]. The key step for the synthesis is the stereoselective construction of the 2-amino-1,3-diol moiety of the molecules. Generally

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• the synthesis of diol by the condensation of styrene and paraformaldehyde in the presence of a Brønsted acid [23][24]. The major breakthrough for this reaction was reported by Hanschke in 1955, when the THP ring was selectively constructed through a Prins reaction involving 3-butene-1-ol and a variety

Kinetics of enzyme-catalysed desymmetrisation of prochiral substrates: product enantiomeric excess is not always constant

• Peter J. Halling

Beilstein J. Org. Chem. 2021, 17, 873–884, doi:10.3762/bjoc.17.73

• -pong second (ketone amination, diol esterification, desymmetrisation in the second half reaction); ping-pong first (diol ester hydrolysis) and ping-pong both (prochiral diacids). For plausible values of enzyme kinetic parameters, the product enantiomeric excess (ee) can decline substantially as the

• prochiral diols. The enzyme reacts with an amino or acyl donor, releasing a first co-product, to give an aminated or acylated enzyme intermediate. This then reacts with the prochiral ketone or diol to generate the chiral products. “Ping-pong, first”. Followed in most lipase or esterase hydrolyses of

• prochiral diol esters. The enzyme reacts enantiospecifically with the ester to release a chiral product, leaving the acyl group attached to the active site. In a second stage the achiral acyl group undergoes hydrolysis by water. In the desymmetrisation of diols (and diacids, below) kinetic amplification can

A chromatography-free and aqueous waste-free process for thioamide preparation with Lawesson’s reagent

• Ke Wu,
• Yichen Ling,
• An Ding,
• Liqun Jin,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2021, 17, 805–812, doi:10.3762/bjoc.17.69

• reckoned that converting compound A to a more polar derivative could probably be a breakthrough. As common knowledge, the more polarized alcohols over EtOH are those diols or polyols, while MeOH was previously ruled out. Ethylene glycol, a basic chemical and the simplest diol, is slightly soluble in

Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

• Emine Salamci and
• Yunus Zozik

Beilstein J. Org. Chem. 2021, 17, 705–710, doi:10.3762/bjoc.17.59

• are reported. Reduction of cyclooctene endoperoxide, obtained by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc yielded a cyclooctene diol followed by acetylation of the hydroxy group, which gave dioldiacetate by OsO4/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to

• should have a cis configuration relative to the protons H-3 and H-4. Next, the reduction of azidotriol 10 by hydrogenation afforded the target aminotriol 12 in 95% yield. For the synthesis of the other aminocyclooctanetriol 18, the diol 6a [33] was reacted with m-CPBA to give trans-epoxide isomer 13 [33

• method for the synthesis of a novel chlorocyclooctanetriol isomer, epoxy-diol 22, which was synthesized in our previous work [31], was hydrolysed by HCl(g) in MeOH, resulting in the formation of two chlorocyclooctanetriol isomers 23 and 24 in an 85:15 ratio (1H NMR) in 96% combined yield (Scheme 5

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• )stoichiometric amounts of diol cleaving agents, other than EG (for instance, PD [239], DEG [240][241]). As a consequence, the depolymerisation step usually results in complex mixtures of oligomers. Moreover, reacting diols may be unstable under the reaction conditions adopted. Hence, if used in excess, a

• chemical recycling to produce novel polyesters [245]. In this process, isosorbide was used as depolymerising diol to give a mixture of differently composed oligomers, whereas succinic acid was added in the second step as polymerising comonomer (Scheme 7). Both steps were efficiently catalysed by

Designed whole-cell-catalysis-assisted synthesis of 9,11-secosterols

• Marek Kõllo,
• Marje Kasari,
• Villu Kasari,
• Tõnis Pehk,
• Ivar Järving,
• Margus Lopp,
• Arvi Jõers and
• Tõnis Kanger

Beilstein J. Org. Chem. 2021, 17, 581–588, doi:10.3762/bjoc.17.52

• chemistry and synthetic biology. Stereo- and regioselective hydroxylation at C9 (steroid numbering) is carried out using whole-cell biocatalysis, followed by the chemical cleavage of the C–C bond of the vicinal diol. The two-step method features mild reaction conditions and completely excludes the use of

• to its toxicity, the oxidation rate affording trans-diols was very slow in comparison to that for cis-diols. Using an even longer reaction time and stoichiometric amount of the reagent, diol 5 was not oxidized to the corresponding dicarbonyl compound 8. However, using NaOCl·5H2O as an oxidant [31

• ], diols 5 and 6 were effectively converted to the corresponding 9,11-secosterols 8 and 9 within one hour at 0 °C (Scheme 3). Compound 8 was isolated as 2:1 mixture together with starting diol 5 and purified further by preparative TLC. Compound 9 was isolated as a single product in 87% yield. Conclusion We

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• [81]. The authors obtained the chiral monoacetate intermediates (R)-78 and (S)-80 by lipase-catalyzed methods. The lipase-catalyzed asymmetric transesterification of prochiral diol 77 and the deacetylation of the prochiral diacetate 79 resulted in the formation of the (R)-monoacetate (R)-78 and (S

Total synthesis of decarboxyaltenusin

• Lucas Warmuth,
• Aaron Weiß,
• Marco Reinhardt,
• Anna Meschkov,
• Ute Schepers and
• Joachim Podlech

Beilstein J. Org. Chem. 2021, 17, 224–228, doi:10.3762/bjoc.17.22

• Lewis acid, while the utilization of 1.5 equivalents led to a significant overreaction with the predominant formation of 5-bromobenzene-1,3-diol (59%) together with a smaller amount of the required product 8 (30%). The subsequent protection with the TBS group yielded the known aryl bromide 9a [24] with

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• ] (“Cyclodextrin–gold nanocluster decorated TiO2 enhances photocatalytic decomposition of organic pollutants” by H. Zhu et al., J. Mater. Chem. A vol. 6, © 2017); permission conveyed through Copyright Clearing Center, Inc. Visible-light-driven conversion of benzyl alcohol to H2 and a vicinal diol or to H2 and

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• transformed into (−)-101 using a three-step sequence. Upon iodination of (−)-101 produced iodide (+)-102 in excellent yield. Deiodination of (+)-102 followed by regioselective dihydroxylation with Sharpless’ AD mix-β reagent [64][65] provided diol (−)-103 as a mixture of stereoisomers. Significantly, the diol

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• second generation Grubbs catalyst 57 in 99% yield. The azabicyclic system (+)-51 underwent dihydroxylation with the OsO4-NMO system to form diol (+)-52 as the only product in 97% yield. Diol (+)-52 was regioselectively protected in the presence of tert-butyldimethylsilane triflate, and triethylamine

Vicinal difluorination as a C=C surrogate: an analog of piperine with enhanced solubility, photostability, and acetylcholinesterase inhibitory activity

• Yuvixza Lizarme-Salas,
• Alexandra Daryl Ariawan,
• Ranjala Ratnayake,
• Hendrik Luesch,
• Angela Finch and
• Luke Hunter

Beilstein J. Org. Chem. 2020, 16, 2663–2670, doi:10.3762/bjoc.16.216

• ] was protected as the benzyl ether then subjected to a Sharpless asymmetric dihydroxylation reaction to furnish the diol 8 in modest yield. The diol 8 was then converted into the cyclic sulfate 9, which was ring-opened using TBAF to furnish the fluorohydrin 10. A Mosher ester analysis of the

Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

• Elizabeth A. Margolis,
• Rebecca J. Keyes,
• Stephen D. Lockey IV and
• Edward E. Fenlon

Beilstein J. Org. Chem. 2020, 16, 2314–2321, doi:10.3762/bjoc.16.192

• ), whereas host 1 and guest 3 would lead to a 75 backbone-atom trefoil (and unknotted macrocycle). Results and Discussion The synthesis of bis-macrocyclic host 1 began by breaking the symmetry of naphthalene-1,5-diol (4) by alkylation of one of the alcohols with 2-azidoethyl mesylate to yield azide 5 in 27

• % yield (Scheme 1). Alkylation of 5 with 1,2-dibromoethane provided key intermediate azido-bromide 6 in 60% yield. This two-step route to 6 is efficient, but the 16% overall yield was lower than desired. An alternate route began by converting diol 4 to bis(2-hydroxyethoxy)naphthalene 7 in 92% yield by

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• on subsequent Tamao–Fleming oxidation provided the exo-diol 18 in an overall good yield with 99% enantiomeric excess (Scheme 3). Furthermore, the diol 18 was converted into the corresponding diketone 19 using pyridinium chlorochromate (PCC) as an oxidizing agent. Interestingly, they have also

Synthesis of 6,13-difluoropentacene

• Matthias W. Tripp and
• Ulrich Koert

Beilstein J. Org. Chem. 2020, 16, 2136–2140, doi:10.3762/bjoc.16.181

• subsequent reduction step using NaBH4 to diol 13 was performed without further purification of the quinone. The low yield for the formation of 13 seems to be an intrinsic instability of its ortho-fluorobenzylic alcohol moiety. Moreover, the compound quantitatively decomposes to 6,13-pentacenequinone 15 in

• 14 then rapidly decomposes to 6,13-pentacenequinone (15) after elimination of HF. The final aromatization of diol 13 to the target molecule 5 proceeded smoothly in 74% yield using SnCl2 in 1,4-dioxane and aqueous HCl [11][12]. F2PEN 5 can be stored under inertgas atmosphere at −20 °C for a month

• -difluoroanthracene. This strategy could be applicable for the synthesis of differently substituted 6,13-difluoropentacenes as well. Structures of pentacene and fluorinated pentacenes. UV–vis spectrum of F2PEN 5 in CH2Cl2. Retrosynthetic analysis of F2PEN 5. Synthesis of F2PEN 5. Decomposition of diol 13 in solution