Characterization of two new degradation products of atorvastatin calcium formed upon treatment with strong acids

• Jürgen Krauß,
• Monika Klimt,
• Markus Luber,
• Peter Mayer and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2085–2091, doi:10.3762/bjoc.15.206

• process (stereoisomers, products resulting from impure starting materials or side reactions), and only one of these impurities, lactone 2, is most likely a degradation product, resulting from acid-mediated lactonization of the 3,5-dihydroxyheptanoate side chain. A couple of previous publications deal with

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• by electronic circular dichroism spectroscopy’). Functionalization of 3,4-diphenylbutanal (1) at the α-position can lead to four stereoisomers, but photooxygenation catalyzed by secondary amines 16, 17 and 18 furnished only two of them. The diastereoisomeric ratio was always close to 2:1, the same as

• its rather simple structure diol 6 was not previously reported in the literature. The ratio of stereoisomers 6 was determined by HPLC analysis while the absolute configuration of the newly created stereocenter was established using a chiroptical spectroscopic method. Samples of stereoisomers syn-6 and

• based on the ECD spectra recorded for pure syn-6 and anti’-6 diols (Figure 1b) [29]. The comparison of the experimental ECD curves with the calculated ones for two possible stereoisomers (2R,3R) and (2R,3S) allowed for unambiguous assignment of (2R,3R) absolute configuration to the syn-6 isomer and (2R

Analysis of sesquiterpene hydrocarbons in grape berry exocarp (Vitis vinifera L.) using in vivo-labeling and comprehensive two-dimensional gas chromatography–mass spectrometry (GC×GC–MS)

• Philipp P. Könen and
• Matthias Wüst

Beilstein J. Org. Chem. 2019, 15, 1945–1961, doi:10.3762/bjoc.15.190

• stereoisomers α-ylangene and β-ylangene are formed via (R)-(+)-germacrene D. Furthermore, our results showed that the isomeric compounds α-cubebene and β-cubebene are also formed via (S)-(−)-germacrene D. In addition, 6 aromatic sesquiterpene hydrocarbons from the headspace of grape berry exocarp of the red

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• ). The 1H spectrum of 5R is much more complex. Ha of the anthracene stopper was observed as two overlapping doublets, and three triazole singlets and more than two sets of CB[6] signals were observed, showing that 5R was obtained as a mixture of stereoisomers with very different chemical environments at

• structural assignment of 5R may not be straightforward unless more detailed structural characterization such as X-ray crystal data is available. Nevertheless, the observation that 5R was obtained as different stereoisomers further strengthens the proposal that it is the full occupancy of the axle by the

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

• four stereoisomers with low (ca. 3:1) diastereoselectivity and in a non-enantioselective manner (Scheme 46) [21]. Undoubtedly, it was the 1,3-dipolar cycloaddition of the azomethine ylide 180 with an electron-rich alkene. Fortunately, cycloadducts (2R,3R,4S)-, (2S,3S,4R)-, (2R,3S,4R)- and (2S,3R,4S

• [110]. ʟ-1-Deoxynojirimycin ((2S,3S,4S,5R)-200) and five of its stereoisomers were synthesized in a unique approach using (2S,1'R)-5b as a starting material [88]. When the aziridine ketone (2S,1'R)-201 was treated with a NaBH4/ZnCl2 mixture the aziridine alcohol (2S,1'R,1''R)-202 was stereoselectively

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• ), compound 9 undergoes two types of reactions. When the substrate is ionized in the presence of benzene and CF3SO3H, the arylation product 10 is formed as the major product (Scheme 3). Presumably, compound 10 is formed as a mixture of meso and dl stereoisomers. Similar reaction products were observed in our

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

• Anthony Choi,
• Rebecca M. Morley and
• Iain Coldham

Beilstein J. Org. Chem. 2019, 15, 1480–1484, doi:10.3762/bjoc.15.149

• with triethylamine promoted the reaction of the resulting quinolinium ylides (formally azomethine ylides) with electron-poor alkenes by conjugate addition followed by cyclization or by [3 + 2] dipolar cycloaddition. The pyrroloquinoline products were formed as single regio- and stereoisomers. These

• with N-methylmaleimide in the presence of triethylamine in methanol to give the desired adducts 15a and 15b as single stereoisomers (Scheme 5). The stereochemistry of product 15a was confirmed by single crystal X-ray analysis (see Supporting Information File 1) and matches the relative configuration of

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

• Xiujun Liu,
• Xiang Ma and
• Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

• -generated nitrile oxide, which showed inferior selectivity and afforded regio-/stereoisomers [43]. NMR analysis assisted the identification of various isomeric isoxazoline-linked chlorin products. Here, we would like to report an artificial vinylporphyrin 2, which has been designed to control the

Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Ruben Pomar Fuentespina,
• José Angel Garcia de la Cruz,
• Gabriel Durin,
• Victor Mamane,
• Jean-Marc Weibel and
• Patrick Pale

Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141

• coupling reactions of either terminal or organometallic alkynes with vinyl halides or of alkynyl halides with vinylic organometallics [20]. However, both routes may lead to mixtures of stereoisomers and synthetic approaches to stereodefined substituted α-enynes remain scarce and thus still represent a

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• cytotoxicity [9]. However, it is of great importance to obtain all stereoisomers for the study of biological activity. Therefore, the development of methods for the asymmetric synthesis of polyfunctional sulfones is valuable. The most notable of them are Ag- and Cu-catalyzed 1,3-dipolar cycloaddition reactions

• 8a or 9a. Оne of the stereoisomers can be formed directly during the reaction. To test this hypothesis, we decided to study the evolution of dr on the course of reaction by 1H NMR spectroscopy (Figure 3). The reaction of sulfone 5a with ω-nitrostyrene (6a) was chosen as the model reaction. Conversion

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

• Alexander F. de la Torre,
• Gabriel S. Scatena,
• Oscar Valdés,
• Daniel G. Rivera and
• Márcio W. Paixão

Beilstein J. Org. Chem. 2019, 15, 1210–1216, doi:10.3762/bjoc.15.118

• chromatography on silica gel using n-hexane/EtOAc as eluent. Enantiomeric excess (ee) was determined by chiral HPLC analysis through comparison with the authentic racemic material. Assignment of the stereoisomers was performed by comparison with literature data. Synthesis and characterization Prolyl pseudo

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

• Emeline Benoit,
• Ahmed Fnaiche and
• Alexandre Gagnon

Beilstein J. Org. Chem. 2019, 15, 1162–1171, doi:10.3762/bjoc.15.113

• . Treatment of 1,3-bis(phenylthio)propanes 22 with butyllithium is another way of accessing substituted aryl cyclopropyl sulfides 23 (Scheme 2e) [23]. However, in addition to requiring a very strong base, the generation of regio- and stereoisomers from a complex starting material reduces the attractiveness of

Cyclopropene derivatives of aminosugars for metabolic glycoengineering

• Jessica Hassenrück and
• Valentin Wittmann

Beilstein J. Org. Chem. 2019, 15, 584–601, doi:10.3762/bjoc.15.54

• . Since the stereoisomers resulting from the chiral centers at the methylcyclopropyl (and also methylcyclopropenyl) residues were not readily separable, we always used mixtures of isomers. Small amounts of the ManN derivatives were deacetylated with sodium methoxide in methanol and a subsequent sialic

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

• envisaged that the enantiomers of 4 were ideal substrates for the asymmetric synthesis of different stereoisomers of 2. Several biocatalytic protocols for the preparation of (R) or (S)-4 were reported earlier. The hydrolysis of the corresponding acetate with crude enzyme preparations from pig liver and

Reusable and highly enantioselective water-soluble Ru(II)-Amm-Pheox catalyst for intramolecular cyclopropanation of diazo compounds

• Hamada S. A. Mandour,
• Yoko Nakagawa,
• Masaya Tone,
• Hayato Inoue,
• Nansalmaa Otog,
• Ikuhide Fujisawa,
• Soda Chanthamath and
• Seiji Iwasa

Beilstein J. Org. Chem. 2019, 15, 357–363, doi:10.3762/bjoc.15.31

• determined to be (1S,5R,6R) by single-crystal X-ray diffraction analysis (Supporting Information File 1) [51]. Since the stereoselectivity of products depends on the cis/trans geometry of the reactants, other stereoisomers such as the (1S,5R,6S) product was not formed in this catalytic cyclopropanation

• . During the reaction process, no other stereoisomers were obtained. Next, the reusability of water-soluble catalyst cat. 2 was examined. After separation of the ether layer, the aqueous phase was extracted with diethyl ether several times until no product remained. A new solution of trans-allylic diazo

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• - or 24-fold molar excess of olefin relative to silsesquioxane. The reaction with styrene led to the formation of the expected product with an exclusive E-stereochemistry around the newly formed C=C double bond, while aliphatic α-alkenes (1-hexene, allyltrimethylsilane) gave a mixture of stereoisomers

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

• giant neurons of the African giant snail appeared to be sensitive to various extents to all stereoisomers of 2 [21][22][23]. Hydroxyglutamic acids are widely spread in nature, especially in plants but they were also found in other species or as components of more complex molecules of interesting

• ][44]. Natural occurrence as well as possibilities of glutamate-like biological activity modulated by additional hydrogen bonding with hydroxy groups inspired the interest in the synthesis of stereoisomers of hydroxyglutamic acids 2–4 (Figure 2). Since they contain two or three stereogenic centers

• with 69 and (2S,4S)-3 [78]. Two other stereoisomers were synthesized in a similar way from (R)-67. By a nitrone–acrylate cycloaddition The isoxazolidine ring can be considered as another cyclic precursor to 4-hydroxyglutamic acids due to the easy cleavage of the N–O bond and high trans

Volatiles from the hypoxylaceous fungi Hypoxylon griseobrunneum and Hypoxylon macrocarpum

• Jan Rinkel,
• Alexander Babczyk,
• Tao Wang,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 2974–2990, doi:10.3762/bjoc.14.277

• diastereomers usually also produce very similar mass spectra [16], a phenomenon that is also reported for E and Z stereoisomers and can lead to wrong structural assignments, if no authentic standards are used for comparison [17]. We have recently reported on two chlorinated aromatic compounds from an endophytic

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• presence of [Ir(ppy)(dtbpy)](PF6) and iPr2NEt as photoredox catalyst and a sacrificial reagent, respectively, in acetonitrile under an atmospheric pressure of CO2 (Scheme 20). 1-Phenyl-1-propyne (16n) afforded hydrocarboxylated products as a mixture of regio- and stereoisomers. 4-Octyne (16b) afforded the

Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

• Piotr Pomarański,
• Piotr Roszkowski,
• Jan K. Maurin,
• Armand Budzianowski and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214

• , Poland 10.3762/bjoc.14.214 Abstract Background: Atropisomers are very interesting stereoisomers having axial chirality resulting from restricted rotation around single bonds and are found in various classes of compounds. ortho-Substituted arylpyridines are an important group of them. A regio- and

• of 3,4,5-tribromo-2,6-dimethylpyridine with 2-methoxyphenylboronic acid under Suzuki–Miyaura reaction conditions gave the mixture of three atropisomeric stereoisomers of 3,4,5-tri-(2-methoxyphenyl)-2,6-dimethylpyridines which were separated by column chromatography and characterized by NMR

• stereoisomers of 3,4,5-tris(2-methoxyphenyl)-2,6-dimethylpyridines determined by X-ray analysis [38]. Graphical representation of kinetic, time-dependent 1H NMR analysis of (syn)-7 (100 °C). Graphical representation of kinetic, time-dependent 1H NMR analysis of (syn)-10 (120 °C). HT-NMR (300 MHz, DMSO-d6

The enzymes of microbial nicotine metabolism

• Paul F. Fitzpatrick

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

• enzyme is a likely candidate for the enzyme catalyzing the first step in the metabolism of both stereoisomers [23]. The subsequent step requires an additional enzyme. The pAO1 plasmid contains the gene for a D-6-hydroxynicotine oxidase (DHNO) in addition to that for LHNO. The product of the reaction

• to that of LHNO and several members of the MAO family, consistent with Nox being a nicotine oxidase similar to NicA2. Nox is reported to be able to oxidize both stereoisomers of nicotine equally well, in contrast to the stereospecificity of LHNO and DHNO. Pseudooxynicotine amine oxidase, the enzyme

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

• -flat wheels, such as calixarenes or cyclodextrins, are threaded along an axle to give a pseudo[3]rotaxane architecture V–VII (Figure 2), where three sequential stereoisomers can arise. We showed that this stereoisomerism can be effectively controlled when two calix[6]arene wheels are threaded along a

• stereoisomers (V–VII) reported by our group [19][20][21]. The possible 8 discrete conformations of a calix[6]arene macrocycle [26]. Diastereoisomeric pseudorotaxanes obtained by threading a directional calixarene wheel with directional axles. Possible mechanism for the formation of the two atropoisomeric pseudo

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• ]. Calixarenes are easily functionalized at both their upper and lower rims with various stereoisomers obtainable; the initial macrocycles can be synthesized in a simple manner, they are not toxic, etc. [17][18][19][20][21][22]. Amphiphilic calixarenes are particularly interesting because they can be regarded as

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

• oxidative coupling reaction with 2,4-bis(trimethylsilyl)uracil (29) using diacetoxyiodobenzene, respectively, and the results are shown in Table 3. The reaction of 96a gave an inseparable mixture containing 4 stereoisomers of 97a–d with a ratio of 6:10:2:1.5, which was determined based on the analysis of

• cytosine analogues [63]. During the course of conversion, all the stereoisomers were separated. Among them, only the cytosine derivative 99 showed weak anti-HIV activity (Scheme 13 and Table 3). An oxidative coupling reaction for synthesizing carbocyclic nucleosides mediated by hypervalent iodine was

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