Regiodefined synthesis of brominated hydroxyanthraquinones related to proisocrinins

• Joyeeta Roy,
• Tanushree Mal,
• Supriti Jana and
• Dipakranjan Mal

Beilstein J. Org. Chem. 2016, 12, 531–536, doi:10.3762/bjoc.12.52

• at δ 111.7 ppm in the 13C NMR spectrum. The Michael acceptor 13 was prepared according to the literature procedure starting from cyclohex-3-enecarbaldehyde (25) [38]. The diol 26 was oxidized with activated MnO2, leading to selective oxidation of the secondary alcohol forming 27 in 83% yield. The

• lactol 34 with methylmagnesium bromide afforded diol 35 in 72% yield. Selective oxidation of the allylic alcohol group in 35 with MnO2, followed by acetylation of the secondary hydroxy group with acetyl chloride, triethylamine and DMAP furnished cyclohexenone 36 (Scheme 5). The Hauser annulation of

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• , diastereoselective reduction of the cross-benzoin products with NaBH4 afforded valuable syn-diol products. Goodman and Johnson disclosed a dynamic kinetic resolution of β-halo-α-ketoesters via NHC-catalysed asymmetric cross-benzoin reaction. Here, the cross-benzoin reaction of aromatic aldehydes with β-stereogenic-α

Self and directed assembly: people and molecules

• Tony D. James

Beilstein J. Org. Chem. 2016, 12, 391–405, doi:10.3762/bjoc.12.42

• acid spontaneously self-assemble to quantitatively form a stable complex. Interestingly, when the chirality of the binol or amine was fixed the 1H NMR of the complexes formed using a scalemic mixture of the other chiral partner (diol or amine) results in a 1H NMR where signals due to both

• diastereomeric complexes are clearly separated. The diastereomeric imine signals are particularly useful since they are in a region of the spectra clear of interference from signals due to the binol (diol) or amine. Integration of the pair of imine signals provides a diastereomeric ratio which can be related to

• the enantiomeric excess of the original scalemic mixture of binol (diol) or amine (Figure 15). The three-component system was very versatile and we could use the complexes to determine the enantiomeric excess (ee) of amines [69][70], diamines [71], amino alcohols [72], hydroxylamines [73] and diols

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• of DIBAL-H to produce 2A,3B-diol 46 from TRIMEB (Scheme 9) [90]. The two remaining free alcohols were then functionalized with the α-nucleophile and an imidazole group [88]. The acid–base dyad thus obtained is likely to improve the hydrolysis of nerve agents. The imidazole group was first introduced

New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

• Agnieszka Hryniewicka,
• Szymon Suchodolski,
• Agnieszka Wojtkielewicz,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 2795–2804, doi:10.3762/bjoc.11.300

• , Table 2) were obtained in high and very high yields. Alkenes were converted almost quantitatively and the excess of (Z)-but-2-ene-1,4-diol diacetate was recovered. Some side products of self-metathesis (SM) of terminal alkenes were isolated. It should be added that two terminal olefins (entry 4, Table 2

• ) gave also SM products besides the desired CM products. Furthermore, more dimeric products gave allyloxybenzene than hex-5-enyl acetate. It is worth noting that the CM reaction between styrene and (Z)-but-2-ene-1,4-diol diacetate (entry 1, Table 2) was highly efficient (97% yield) using catalyst 9

Genicunolide A, B and C: three new triterpenoids from Euphorbia geniculata

• Alia Farozi,
• Javid A. Banday and
• Shakeel A. Shah

Beilstein J. Org. Chem. 2015, 11, 2707–2712, doi:10.3762/bjoc.11.291

• -ene-5,8-lanostadiene-3β-ol, 3β,24S,25-trihydroxycycloartane, 3β,24(R),25-trihydroxy-cycloartane, 24-methylenecycloartan-3β-ol [16], cycloart-23-ene-3,5-diol [17], lupeol, lupeol acetate, ginnone, ambrein, lupeone [18], 24-methylenecycloartanol [19], cycloart-25-en-3β,24-diol [20] and cycloart-22-ene

• -3β,25-diol [21]. In addition, nor-isoprenoids and coumarins have also been reported from few species of Euphorbia [22][23][24]. Euphorbia geniculata Orteg. [25][26], is a wild weed found in the Jammu region of India [27]. The plant is locally used for the treatment of bacterial infections and

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• benzylic bromination followed by elongation of the C3 unit [22]. To this end, the ester group at the C1 position of 15 was reduced by lithium borohydride, and the resultant 1,3-diol protected to give acetal 16 [16]. After various experiments, selective bromination of the methyl group on the aromatic ring

Assembly of synthetic Aβ miniamyloids on polyol templates

• Sebastian Nils Fischer and
• Armin Geyer

Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284

• strands, which are expected to push the esterification towards quantitative conversion. Compound 5 combines side-chain cis-diol functionality for boronic ester formation and the potential of controlled oligomerization by peptide chemistry. Azido ester 5 is a precursor of the dipeptide Hot=Tap, which

• serves as a β-turn mimic in peptides and proteins [24][25][26]. Alternatively, Fmoc-Hot=Tap-OH (8, Figure 5) is available for oligomerization on SPPS to templates of adjustable length with a systematic increase of the number of cis-diol functions assembled on a rigid peptide backbone. In solution

• -membered (triangle, 3) esters. The overlapping resonances in the 1H NMR spectra of the esters in the region between 4 and 5 ppm are resolved in the HSQC spectrum, where the alpha-carbons are visible below 50 ppm and the CH–OB groups between 65 and 80 ppm. Diol 5 (6.08 mg, 20.0 μmol, 1.0 equiv) and 3

Recent advances in copper-catalyzed asymmetric coupling reactions

• Fengtao Zhou and
• Qian Cai

Beilstein J. Org. Chem. 2015, 11, 2600–2615, doi:10.3762/bjoc.11.280

• stereogenic centers, derived from tartaric acid, giving the product as a single isomer in good yield (Scheme 11). Sugimura et al. [31] expanded this method by introducing chiral 1,3-diol-derived tethers into the substrates, delivering the corresponding coupling products in excellent diastereoselectivity

• -permethyl-tellimagrandin I. Total synthesis of (+)-gossypol. Total synthesis of (−)-mastigophorene A. Total synthesis of isokotanin. Synthesis of dimethyl[7]thiaheterohelicenes. Intramolecular coupling with chiral ortho-substituents. Chiral 1,3-diol-derived tethers in the diastereoselective synthesis of

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

• Zhan-Jiang Zheng,
• Ding Wang,
• Zheng Xu and
• Li-Wen Xu

Beilstein J. Org. Chem. 2015, 11, 2557–2576, doi:10.3762/bjoc.11.276

• highest activity. In 2010, Nandurdikar et al. linked the two (or four) molecules of NO donor prodrugs together through the triazole spacers [22], which has potential application as NO-releasing materials. They first prepared the benzylidene-protected 2,2-di(azidomethyl)propane-1,3-diol containing the

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• conditions [48] and an ensuing desilylation furnished a diol. In order to introduce a leaving group for the following key step, the secondary hydroxy group was tosylated to afford 79. Once again, a stereospecific Grob fragmentation of tosylate 79 served as the key step for the synthesis of the

• commenced with the preparation of diol 96 by a palladium-catalyzed hydrostannylation of 2-butyne-1,4-diol (95). Regioselective silylation with tert-butyldimethylsilyl chloride of the sterically less hindered alcohol, iodination and silylation of the primary alcohol with trimethylsilyl chloride gave vinyl

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

• epoxidation of 5 with tert-butylhydroperoxide (TBHP) in toluene gave 6 ([α]D +34.2° (c 1.3, CHCl3)) in 95% yield [9][22]. Then, the diol 7 was obtained in 85% yield from the reduction of epoxide 6 with LiAlH4 in THF at 0 °C. The diol 7 was easily purified by crystallization (85% yield, n-hexane at −50 °C up

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• refluxing DCM with 1 mol % of catalyst 69. After reaction completion (97% isolated yield) and a single extraction with D2O, (Z)-but-2-ene-1,4-[2H]-diol was added to the water phase and isomerization to the trans isomer 71 was completeted after 1 h, with no decrease in activity (94% isolated yield) observed

Cross metathesis of unsaturated epoxides for the synthesis of polyfunctional building blocks

• Meriem K. Abderrezak,
• Kristýna Šichová,
• Nancy Dominguez-Boblett,
• Antoine Dupé,
• Zahia Kabouche,
• Christian Bruneau and
• Cédric Fischmeister

Beilstein J. Org. Chem. 2015, 11, 1876–1880, doi:10.3762/bjoc.11.201

• cross metathesis of 1 with methyl acrylate was transformed by means of nucleophilic ring-opening of the epoxide to furnish a diol, an alkoxy alcohol and an amino alcohol in high yields. Keywords: cross metathesis; epoxide; ruthenium catalysts; tandem reactions; Introduction Catalytic carbon–carbon

• post-transformation of 4 by ring-opening of the epoxide moiety. The diol 6, methoxy alcohol 7 and amino alcohol 8 were thus prepared by reacting 4 with water, sodium methoxide and aniline, respectively (Scheme 4). The synthesis of 6 proceeded cleanly and did not require any purification procedure (see

• that was further efficiently transformed into a 1,2-diol, a 1,2-alkoxy alcohol and a 1,2-amino alcohol. This strategy opens the way for numerous potential transformations involving the epoxide but also the functional group of the electron-deficient olefin. In particular, lactones should be accessible

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• derived from cyclopentadiene (111) and 1,4-benzoquinone. The diol 132 was produced by reduction of 131 in an efficient manner. To this end, the bis-O-allylated compound 133 was prepared by an allylation sequence using allyl bromide (37) in the presence of NaH starting with the diol 132, whereas compound

Polythiophene and oligothiophene systems modified by TTF electroactive units for organic electronics

• Alexander L. Kanibolotsky,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2015, 11, 1749–1766, doi:10.3762/bjoc.11.191

• -deficient acetylene compounds (Scheme 6). By reacting 23 with 24a this method provides diester 25a in good yield [63]. Compound 25a can be reduced to diol 25d [64] and further converted by either the Appel method [59] or by reaction with PBr3 [65] into dibromomethyl compound 21, which is required for

• the synthesis of 25c – a compound required for synthetic pathway B – was found to be repeated sequential lithiation of vinylene trithiocarbonate (26) [67] followed by subsequent trapping of the lithium organic species with thiophenecarboxaldehyde 27 [60]. The diol 25e, formed as a product of this

Engineering Pichia pastoris for improved NADH regeneration: A novel chassis strain for whole-cell catalysis

• Martina Geier,
• Christoph Brandner,
• Gernot A. Strohmeier,
• Mélanie Hall,
• Franz S. Hartner and
• Anton Glieder

Beilstein J. Org. Chem. 2015, 11, 1741–1748, doi:10.3762/bjoc.11.190

• products (2R,3R)-butane-2,3-diol and meso-butane-2,3-diol obtained after 16 h reaction time are shown in Figure 4A. Performing the BDH1-catalyzed acetoin reduction with the wild type strain P. pastoris CBS7435 resulted in an average conversion of ~5% (40 individual clones tested). Employing the single

• cassette, reaching ~35% and ~8% substrate conversion, respectively. As for the recombinant strains, two products were detected, namely (2R,3R)-butane-2,3-diol and meso-butane-2,3-diol. Conclusion Efficient cofactor recycling is not only required for an optimal enzyme performance, but is also crucial to

• )-acetoin: 2.32 min, (2R,3R)-butane-2,3-diol: 8.27 min, meso-butane-2,3-diol: 8.90 min. Simplified schematic representation of the methanol utilization pathway in Pichia pastoris. The main pathways and the respective enzymes are shown. AOX: alcohol oxidase; FLD: glutathione-dependent formaldehyde

Design and synthesis of propellane derivatives and oxa-bowls via ring-rearrangement metathesis as a key step

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1727–1731, doi:10.3762/bjoc.11.188

• further subjected to RRM with G-I catalyst in the presence of ethylene to deliver the hexacyclic oxa-bowl 1c in quantitative yield (Scheme 3). Having the C-allylated DA adducts 4a,b in hand, compound 4a was reduced with diisobutylaluminium hydride (DIBAL-H) at −74 °C to furnish diol 8a in 81% yield along

• with a minor amount of compound 9 (8%). The formation of compound 9 may be explained on the basis of a retro-DA reaction [36] followed by reduction and elimination. In the same way, reduction of C-allyl compound 4b under similar reaction conditions gave diol 8b in 88% yield. In the next step, diols 8a

An efficient synthesis of N-substituted 3-nitrothiophen-2-amines

• Sundaravel Vivek Kumar,
• Shanmugam Muthusubramanian,
• J. Carlos Menéndez and
• Subbu Perumal

Beilstein J. Org. Chem. 2015, 11, 1707–1712, doi:10.3762/bjoc.11.185

• , 28040 Madrid, Spain 10.3762/bjoc.11.185 Abstract A novel protocol for the synthesis of 3-nitro-N-aryl/alkylthiophen-2-amines in good yields from the reaction of α-nitroketene N,S-aryl/alkylaminoacetals and 1,4-dithiane-2,5-diol in the presence of K2CO3 in refluxing ethanol is described. This

• associated with the lack of regioselectivity and difficult isomer separation [23]. Other methods for the synthesis of 2,3-disubsituted thiophenes include the reactions of (i) 1,4-dithiane-2,5-diol with nitroalkenes [24], activated nitriles [25] and cyanoacetamide [26]; (ii) 3-nitrothiophene with Grignard

• goals of green chemistry [32]. In this context, we wish to report herein a new and efficient synthesis of 3-nitro-N-aryl/alkylthiophen-2-amines based on domino reactions between α-nitroketene N,S-aryl/alkylaminoacetals and 1,4-dithiane-2,5-diol, the dimer of 2-mercaptoacetaldehyde (Scheme 2). This work

Star-shaped tetrathiafulvalene oligomers towards the construction of conducting supramolecular assembly

• Masahiko Iyoda and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2015, 11, 1596–1613, doi:10.3762/bjoc.11.175

• doping with iodine produced black complexes which exhibited electric conductivities of σrt = 2.7 × 10−3–2.4 × 10−2 S cm−1 in spite of the non-planarity of the molecular frame of 39–44. The pyridazine-3,6-diol-annulated TTF derivative 45 produced trimer 46 via hydrogen bonds in a THF–H2O solution (Scheme

• tris(TTF)[18]annulene 32. Star-shaped TTF oligomers 38–43. Pyridazine-3,6-diol-TTF 45 and its trimer 46. Redox potentials of 16–19 and absorption maxima of monocations 16•+, 17•+, 18•+ and 19•+, and dications 162+, 172+, 182+ and 192+ [25][59]. Association (dimerization) constants and thermodynamic

Dicarboxylic esters: Useful tools for the biocatalyzed synthesis of hybrid compounds and polymers

• Ivan Bassanini,
• Karl Hult and
• Sergio Riva

Beilstein J. Org. Chem. 2015, 11, 1583–1595, doi:10.3762/bjoc.11.174

• traditional polymerization methods [52]. Binns et al. summarized the attempts to scale up synthesis of polyesters by enzyme catalyzed polycondensation of adipic acid and hexane-1,6-diol in a very well-worth reading article [53]. They discussed the very slow progress in achieving high molecular weight polymers

• . For this, they used CAL-B in a two step synthesis, started at a low vacuum and then increased the vacuum to drive the reaction to completion [55]. The dicarboxylic acid and the diol were employed in equal molar amounts, while the amount of ethyl glycolate was varied. Polymers with a high molecular

• polymerization using only the primary alcohols of the diol, and not the secondary hydroxy group of malic acid. A few years earlier Kato et al. showed that both enantiomers of dimethyl 2-mercaptosuccinate and 1,6-hexanediol were polymerized by CAL-B, while other lipases failed to give long polymers [63]. In the

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• process. We found, however, that diol contamination could be largely suppressed when denser dispersions of P25 (1 mg mL−1, ≈0.75 equiv) were employed resulting in the desired alcohols. Ketone hydrogenations were less successful. Aryl aldehydes with either electron-releasing or electron-withdrawing

Towards inhibitors of glycosyltransferases: A novel approach to the synthesis of 3-acetamido-3-deoxy-D-psicofuranose derivatives

• Maroš Bella,
• Miroslav Koóš and
• Chun-Hung Lin

Beilstein J. Org. Chem. 2015, 11, 1547–1552, doi:10.3762/bjoc.11.170

• ). Subsequently, the selective protection of the primary hydroxy group in diol 5 as trityl ether under standard conditions followed by the oxidation of the free secondary hydroxy group in 3-acetamido-3-deoxy-4,5-O-isopropylidene-6-O-pivaloyl-1-O-trityl-D-altritol (6) with Dess–Martin periodinane yielded a

Design and synthesis of hybrid cyclophanes containing thiophene and indole units via Grignard reaction, Fischer indolization and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Mukesh E. Shirbhate

Beilstein J. Org. Chem. 2015, 11, 1514–1519, doi:10.3762/bjoc.11.165

• started with a Grignard addition reaction. In this context, commercially available thiophene-2,5-dicarbaldehyde (4) was reacted with the Grignard reagent [23] derived from 5-bromo-1-pentene to give diol 6 as a diastereomeric mixture (Scheme 1). Alternatively, the dialdehyde 4 can be prepared by using the

• Vilsmeier–Haack reaction starting with the thiophene [33]. Later, diol 6 was oxidized with MnO2 [34] to deliver diketone 3. Our attempts to realize the RCM product 2 with dione 3 via a reaction with Grubbs’ catalyst failed to give the expected cyclized product. In most instances, we observed the degradation

• of a higher analogue containing seven carbon alkenyl chains was undertaken. To achieve this goal, thiophene dicarbaldehyde 4 was subjected to a Grignard addition reaction with hexenylmagnesium bromide which gave diol 6a as a mixture of diastereomers. Further, the diol was subjected to an oxidation

Design and synthesis of polycyclic sulfones via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1373–1378, doi:10.3762/bjoc.11.148

• synthesized from the functionalized tricyclic sulfone 2 by RRM sequence. The sulfone 2 may be prepared from the dimesylate 3, which in turn, can be assembled from the known anhydride 4 via reduction followed by mesylation of the resulting diol. Compound 4 could be prepared via DA reaction starting with

• freshly cracked cyclopentadiene and maleic anhydride (Figure 1). To realize the strategy shown in Figure 1, we started with the preparation of the known compound 4 [29][30]. Later, the DA adduct 4 was reduced with LiAlH4 to deliver the corresponding diol (95%) [31], which was subsequently treated with