Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• stereoisomeric directional pseudo[2]rotaxanes, rotaxanes, and catenanes. Also in this case [38], we were able to obtain a stereoselective threading of the cone calix[6]arene-wheel with alkylbenzylammonium axles (Figure 4b), in which the endo-alkyl pseudo[2]rotaxane stereoisomer was the favoured one [38]. The

Heterogeneous acidic catalysts for the tetrahydropyranylation of alcohols and phenols in green ethereal solvents

• Ugo Azzena,
• Massimo Carraro,
• Gloria Modugno,
• Luisa Pisano and
• Luigi Urtis

Beilstein J. Org. Chem. 2018, 14, 1655–1659, doi:10.3762/bjoc.14.141

• to acid-catalyzed deprotection with H2SO4@SiO2 (25 wt % [33] as depicted in Scheme 3). Alcohol 1i, was recovered as a single stereoisomer, identical to the commercially available starting material, as determined by 1H and 13C NMR analysis of the crude reaction mixture (see Supporting Information File

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• %) along with the N7 stereoisomer (10%). These results support the above-mentioned hypothesis. Finally, 4'-thioadenosine (49) was synthesized by treating 45 with TFA followed by methanolic ammonia [46] (Scheme 5). The same group attempted to apply the oxidative coupling reaction to the synthesis of

Volatiles from three genome sequenced fungi from the genus Aspergillus

• Jeroen S. Dickschat,
• Ersin Celik and
• Nelson L. Brock

Beilstein J. Org. Chem. 2018, 14, 900–910, doi:10.3762/bjoc.14.77

• from cantaloupe a structural revision to the Z stereoisomer is proposed. Ethyl (Z)-hept-4-enoate also occurs in Aspergillus clavatus and was identified by synthesis of an authentic standard. Keywords: Aspergillus; GC–MS; genomics; terpenes; volatiles; Introduction Ascomycete fungi are a highly

•  2 and Scheme 4). In addition, small amounts of the sesquiterpenes β-elemene (21a), germacrene D (22), β-ylangene (23) and its stereoisomer β-copaene (24) were found. All these sesquiterpenes require a 1,10-cyclisation of FPP to the (E,E)-germacradienyl cation (N). Its deprotonation leads to

• from cantaloupe (Curcumis melo) and tentatively identified as ethyl (E)-hept-4-enoate [44], but the E stereoisomer should elute significantly later than the Z isomer. Likely, the reported compound is the same as found here and the structure requires correction to ethyl (Z)-hept-4-enoate. Further ethyl

Volatiles from the tropical ascomycete Daldinia clavata (Hypoxylaceae, Xylariales)

• Tao Wang,
• Kathrin I. Mohr,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 135–147, doi:10.3762/bjoc.14.9

• 11 were separable by GC on a homochiral stationary phase, one of which matched the natural product in terms of same retention times and mass spectra (Figure 3). To clarify the relative and absolute configuration of the natural stereoisomer of 11 an enantioselective synthesis was performed (Scheme 5

Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

• Tathagata Mukherjee,
• Soumik Biswas,
• Andreas Ehnbom,
• Subrata K. Ghosh,
• Ibrahim El-Zoghbi,
• Nattamai Bhuvanesh,
• Hassan S. Bazzi and
• John A. Gladysz

Beilstein J. Org. Chem. 2017, 13, 2486–2501, doi:10.3762/bjoc.13.246

• helical chiralities (see Figure S2, Supporting Information File 1), affording a meso stereoisomer. Finally, attempts have been made to extend the preceding chemistry in several directions. In screening experiments, all of the fluorous iodine(III) dichlorides assayed, as well as PhICl2, were competent for

Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence

• Attila Márió Remete,
• Melinda Nonn,
• Santos Fustero,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2017, 13, 2364–2371, doi:10.3762/bjoc.13.233

• protocol compound (±)-3 was obtained in a modest yield (15%) that could be slightly increased to 25% by the addition of DBU to the reaction mixture (Scheme 1). In contrast to (±)-1, its stereoisomer (±)-4, afforded in the reaction with 1.5 equiv of Deoxofluor in the presence of 4 equiv of DBU, according to

• the base the yields of (±)-10 and (±)-11 decreased to 10% and 17%, respectively. Unfortunately and surprisingly, diol (±)-12 (derived from trans-2-aminocyclohex-4-ene carboxylic acid) [23][24][25][26] a stereoisomer of (±)-8, in the reaction with either 1 equiv or excess of Deoxofluor did not give any

• identifiable product. However, according to earlier observations on the effect of DBU the reaction in the presence of this base afforded keto ester (±)-13 in 41% yield. In contrast to the stereoisomer (±)-8, reaction of diol (±)-12 with Deoxofluor took place at the C-5 hydroxy group leading to intermediate T11

Homologated amino acids with three vicinal fluorines positioned along the backbone: development of a stereoselective synthesis

• Raju Cheerlavancha,
• Ahmed Ahmed,
• Yun Cheuk Leung,
• Aggie Lawer,
• Qing-Quan Liu,
• Marina Cagnes,
• Hee-Chan Jang,
• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2017, 13, 2316–2325, doi:10.3762/bjoc.13.228

• stereoisomer. Then, if the carbon chain of 8 could be extended by one atom to give the homologated aldehyde 9, fluorination could be repeated and the cycle could continue until the desired number of fluorine atoms was installed. This hypothetical approach had several attractions, including (i) the flexibility

• of being able to generate amino acids of different backbone lengths (e.g., 5, 6, Figure 1) via a unified strategy; (ii) an ability to access any stereoisomer of the target molecules (provided that the stereoselectivity in each fluorination step was catalyst-controlled); (iii) the lower toxicity of

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• the homogeneous products are trans-configured. This assumption is supported by the results obtained with cyclopentadiene and both E- and Z-1b [32]. Whereas the reaction with E-1b led to only one stereoisomer, in the case of Z-1b, exo- and endo-isomers with preserved cis-orientation of the CN and CO2Me

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

• intermediate 45, which was subjected to Wittig olefination. Subsequent aza-Sakurai cyclization of intermediate 46 provided tricyclic derivative 47 as a single stereoisomer, which was then transformed into target myrioneurinol by standard operations. Addition of organometallic reagents to conjugated

Main group mechanochemistry

• Agota A. Gečiauskaitė and
• Felipe García

Beilstein J. Org. Chem. 2017, 13, 2068–2077, doi:10.3762/bjoc.13.204

• halides (AsI3 and SbCl3) have shown that selection of solution or mechanochemical conditions influence product stereoisomer distributions. In this case, the mechanochemical route increases the C1:C3 stereoisomer ratio in complexes 17 and 18 for As and Sb, respectively (see Scheme 7) [100]. The ability to

High-speed vibration-milling-promoted synthesis of symmetrical frameworks containing two or three pyrrole units

• Marco Leonardi,
• Mercedes Villacampa and
• J. Carlos Menéndez

Beilstein J. Org. Chem. 2017, 13, 1957–1962, doi:10.3762/bjoc.13.190

• stereoisomer at the central double bond, which was assumed to be E, while compound 12c, obtained from a 1-homoallyl derivative, was isolated as a 1:1 E/Z mixture (Table 1). Conclusion Symmetrical compounds containing two or three pyrrole or fused pyrrole units joined by a spacer are of interest in the

18-Hydroxydolabella-3,7-diene synthase – a diterpene synthase from Chitinophaga pinensis

• Jeroen S. Dickschat,
• Jan Rinkel,
• Patrick Rabe,
• Arman Beyraghdar Kashkooli and
• Harro J. Bouwmeester

Beilstein J. Org. Chem. 2017, 13, 1770–1780, doi:10.3762/bjoc.13.171

• HdS. (C) Structure of the known stereoisomer 1,11-di-epi-3. NMR data of 3 recorded in C6D6. Supporting Information Supporting Information File 206: Experimental details for gene expression and enzyme incubation experiments, NMR spectra of (1R,3E,7E,11S,12S)-18-hydroxydolabella-3,7-diene, and

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

A new member of the fusaricidin family – structure elucidation and synthesis of fusaricidin E

• Marcel Reimann,
• Louis P. Sandjo,
• Luis Antelo,
• Eckhard Thines,
• Isabella Siepe and
• Till Opatz

Beilstein J. Org. Chem. 2017, 13, 1430–1438, doi:10.3762/bjoc.13.140

• (Figure 1). Thus, an assumed stereoisomer (containing D-allo-Ile) of the new fusaricidin member was synthesized based on analogy to known members of the series and compared to the natural product [8]. Results and Discussion Isolation and structure elucidation The Paenibacillus strain was cultivated on

• single signal set, so the fate of the assumed minor stereoisomer remains unclear and it was probably lost during HPLC purification. The analysis also revealed that the acylation with the GHPD side chain was selective for the amine and no O-acylated product was formed. Side chain protecting groups were

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• protection of the free alcohol and deprotection of the primary PMB-protected alcohol with DDQ, the resulting alcohol was oxidized to the corresponding aldehyde. The crude aldehyde was then directly transformed into the (Z)-α,β-unsaturated ester 62 as a single stereoisomer by a Still–Gennari [72] olefination

Total synthesis of TMG-chitotriomycin based on an automated electrochemical assembly of a disaccharide building block

• Yuta Isoda,
• Norihiko Sasaki,
• Kei Kitamura,
• Shuji Takahashi,
• Sujit Manmode,
• Naoko Takeda-Okuda,
• Jun-ichi Tamura,
• Toshiki Nokami and
• Toshiyuki Itoh

Beilstein J. Org. Chem. 2017, 13, 919–924, doi:10.3762/bjoc.13.93

• linkage [26]. Here we report the total synthesis of TMG-chitotriomycin (1) as a single stereoisomer, which was prepared by automated electrochemical assembly started from a disaccharide building block. Results and Discussion To synthesize the potential precursor 7 of TMG-chitotriomycin (1

Synthesis of D-manno-heptulose via a cascade aldol/hemiketalization reaction

• Yan Chen,
• Xiaoman Wang,
• Junchang Wang and
• You Yang

Beilstein J. Org. Chem. 2017, 13, 795–799, doi:10.3762/bjoc.13.79

• -selective coupling intermediate 12 underwent in situ cyclization to provide hemiketal 13 as the major product in about 50–60% yield (35% overall yield from compound 11). Notably, trace amounts of a stereoisomer and a minor highly polar unknown byproduct were also observed in this cascade reaction. The

Studies directed toward the exploitation of vicinal diols in the synthesis of (+)-nebivolol intermediates

• Runjun Devi and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2017, 13, 571–578, doi:10.3762/bjoc.13.56

• , respectively, in 93% yield. It is to be mention that the NMR spectra and specific rotations of 2 and 29 matched with those reported in the literature [11][14][15]. For the synthesis of compound 3, stereoisomer 29 was subjected to classical two-step Mitsunobu inversion protocol which was successful but poor

Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)

• Alexander Bogdanov,
• Cora Hertzer,
• Stefan Kehraus,
• Samuel Nietzer,
• Sven Rohde,
• Peter J. Schupp,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50

• ) resulted in stronger effects (see Figure 11). Surprisingly, the stereoisomer of 10, 2R-isosarcophytoxide (11) showed no significant deterrence at concentrations up to 2.0% of dry mass. No significant activity could be attributed to the structurally related sarcophytonin B (6) at a concentration up to 1.0

• activity [12]. Remarkable, however, is the inactivity of the (2R)-isosarcophytoxide (11) up to 2% of dry pellet mass, a mere stereoisomer of the active metabolite 10. Such a dependence on stereochemistry may result from a specific interaction with taste receptors in C. solandri lips, oral cavity and

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• to obtain alkylidenoindanedione intermediate 171, which was further converted into racemic benzoabicoviromycin 172 (Scheme 49). The racemic benzoabicoviromycin 172 as well as its (Z)-ethylidene stereoisomer have been screened for in vitro biological activity (antiviral, anticancer and antifungal

Polyketide stereocontrol: a study in chemical biology

• Kira J. Weissman

Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39

• so in principle, 1024 (210) different stereoisomers are possible. Yet, nature reliably assembles only one stereoisomer (at least at detectable levels), at once revealing the strict stereocontrol underpinning the pathway and the importance of synthesizing this particular version. Indeed, the crystal

• resulting enantiomeric materials, it was then shown by autoradiography that acylation of all six DEBS proteins is highly specific for the (2S)-isomer (7) [26], implying that the six AT domains present in the multienzymes select exclusively this stereoisomer (Figure 5). Subsequent studies in vitro with a

• . Analysis of results obtained with KRs from the DEBS [68], tylosin (Tyl) [68][72] and amphotericin [58][61] PKSs (Figure 12), showed that when the KRs selected the correct stereoisomer at the C-2 methyl position, reduction occurred almost exclusively in the native direction; the same result was obtained for

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• compound 23b (Figure 2) and converting the sp3 hybridized carbon atoms C2’ and C3’ into sp2 hybrids shows that the minor stereoisomer is formed by the shielding of the re-face through the tert-butyl group. Hence the major diastereomer 23a is formed by an attack via the less shielded si-face. The same

Biomimetic synthesis and HPLC–ECD analysis of the isomers of dracocephins A and B

• Viktor Ilkei,
• András Spaits,
• Anita Prechl,
• Áron Szigetvári,
• Zoltán Béni,
• Miklós Dékány,
• Csaba Szántay Jr,
• Judit Müller,
• Árpád Könczöl,
• Ádám Szappanos,
• Attila Mándi,
• Sándor Antus,
• Ana Martins,
• Attila Hunyadi,
• György Tibor Balogh,
• György Kalaus (†),
• Hedvig Bölcskei,
• László Hazai and
• Tibor Kurtán

Beilstein J. Org. Chem. 2016, 12, 2523–2534, doi:10.3762/bjoc.12.247

• racemates (2a, 2c/2b, 2d; 3a, 3c/3b, 3d) by HPLC–ECD analysis (Figure 1). The planar structure and absolute configuration of the first-eluted stereoisomer of dracocephins A (±)-2a–d was determined by single-crystal X-ray diffraction analysis as (2R,5”S)-2a [2]. The biosynthesis of these flavonoid

• /TZVP and CAM-B3LYP/TZVP ECD spectra of (2R,5’’R)-2d showed a better agreement with the ECD of 2a (second-eluted stereoisomer) on the basis of the agreement with the 202 nm positive CE but the negative 330 nm n–π* transition was missing from the computed ECDs. The negative 330 nm n–π* transition could

• /TZVP ECD spectra of (2R,5’’S)-2a gave a perfect agreement with the HPLC–ECD of (2R,5’’R)-2d (fourth eluted stereoisomer). All these calculation results would favor the configurational assignment (2R,5’’S)-2d (fourth eluted stereoisomer) and (2R,5’’R)-2a (second eluted stereoisomer), which, however

β-Amino functionalization of cinnamic Weinreb amides in ionic liquid

• Yi-Ning Wang,
• Guo-Xiang Sun and
• Gang Qi

Beilstein J. Org. Chem. 2016, 12, 2372–2377, doi:10.3762/bjoc.12.231

• aziridines derived from compounds 6a-A and 6a-B, the vicinal proton coupling constants were 7.5 Hz and 4.5 Hz, respectively. Therefore, compound 6a-A was assigned as syn-stereoisomer, and compound 6a-B was assigned as anti-stereoisomer. In the 1H NMR spectra of the isolated diastereomers, an obvious and