Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides

• Maryam Khalesi,
• Azim Ziyaei Halimehjani and
• Jürgen Martens

Beilstein J. Org. Chem. 2019, 15, 852–857, doi:10.3762/bjoc.15.82

• . cIsolated yield of one of the diastereomers as pure stereoisomer after several recrystallization steps. ORTEP representation of compound (R*,S*)-4a with thermal ellipsoids at 50% probability. Opposite enantiomer is omitted for clarity. The atom numbering does not follow IUPAC nomenclature. Synthesis of

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• exclusively, so that, after cleavage of the ester groups, epi-scorzodihydrostilbene D (13) was obtained as single stereoisomer (Scheme 4). Obviously, the conditions required in the glycosylation reaction – excess of the Lewis acid and elongated reaction time – resulted in the formation of the

A chemoenzymatic synthesis of ceramide trafficking inhibitor HPA-12

• Seema V. Kanojia,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2019, 15, 490–496, doi:10.3762/bjoc.15.42

• (HPA-12, 1, Figure 1) as the first inhibitor of CERT-mediated ceramide transport [11]. However, the initially determined (1R,3R) configuration of the most active HPA-12 stereoisomer (compound 1, Figure 1) was later revised to (1R,3S) configuration (compound 2, Figure 1) by Berkeš et al. in 2011 [12

• . However, after the structural revision of the most active stereoisomer, Kobayashi et al. synthesized (1R,3S)-HPA-12 (2, Figure 1) using a Zn-catalyzed asymmetric Mannich-type reaction in water, and unambiguously ascertained the revised configuration by X-ray crystallography [14]. The other syntheses of

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• decomposition of this stereoisomer including racemization at Cα. From pentose via 2,3-aziridino-γ-lactone In the so called “2,3-aziridino-γ-lactone methodology” [18][99][100] ribose (or lyxose) is used as a starting material [101][102] which is transformed into the lactone 95 in several steps [99]. Boron

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

• -closing metathesis of 24 now smoothly afforded 25 in high yield. Dihydroxylation selectively yielded the desired stereoisomer of diol 26, which was subsequently protected as isopropylidene acetal. In the next step, after removal of the TBS group and mesylation, attempted substitution with NaN3 resulted

Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic centers

• Zsanett Benke,
• Melinda Nonn,
• Márton Kardos,
• Santos Fustero and
• Loránd Kiss

Beilstein J. Org. Chem. 2018, 14, 2698–2707, doi:10.3762/bjoc.14.247

• catalysts, bicyclic lactone (±)-4 a stereoisomer of (±)-3 furnished olefinated γ-lactone (±)-6 similar to (±)-5 (Scheme 3, Table 2). Unfortunately, ROM reactions, however, took place with total conversions, they were always accompanied by the formation of a significant amount of polymeric materials (ROMP

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• H3B·P(n-C8H17)3 (1%), H3B·P((CH2)13CH2)(n-C8H17) (8%; see text for tie bars that indicate additional phosphorus–carbon linkages, which are coded in the abstract with italics), H3B·P((CH2)13CH2)((CH2)14)P((CH2)13CH2)·BH3 (6·2BH3, 10%), in,out-H3B·P((CH2)14)3P·BH3 (in,out-2·2BH3, 4%) and the stereoisomer

• upon independent syntheses from the dibridgehead diphosphines 2 obtained in Scheme 1 [6], they were assigned as in,out-2·2BH3 (4%) and the stereoisomer (in,in/out,out)-2·2BH3 (2%), as shown in Scheme 2. The depiction of the latter as an out,out (vs in,in) isomer in Scheme 2 is arbitrary, but represents

• rather tedious column chromatography: the dibridgehead diphosphine diborane in,out-2·2BH3, its constitutional isomer 6·2BH3, and its stereoisomer (in,in/out,out)-2·2BH3. It can be inferred from the top spectrum that the three products were the major components and moreover present in approximately equal

The enzymes of microbial nicotine metabolism

• Paul F. Fitzpatrick

Beilstein J. Org. Chem. 2018, 14, 2295–2307, doi:10.3762/bjoc.14.204

• the enzyme. While the dominant form of nicotine found in tobacco is (S)-nicotine, the (R)-stereoisomer is also found at detectable levels [22]. Nicotine dehydrogenase is reported not to be stereospecific, in that it can catalyze the hydroxylation of (R)-nicotine to (R)-6-hydroxynicotine; thus, this

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