Synthesis of 3-substituted isoxazolidin-4-ols using hydroboration–oxidation reactions of 4,5-unsubstituted 2,3-dihydroisoxazoles

• Lívia Dikošová,
• Júlia Laceková,
• Ondrej Záborský and
• Róbert Fischer

Beilstein J. Org. Chem. 2020, 16, 1313–1319, doi:10.3762/bjoc.16.112

• stereochemical results are consistent with our previous findings on the direct dihydroxylation and epoxidation reactions of 4,5-unsubstituted 2,3-dihydroisoxazoles [9][10][11][12]. To invert the relative C-3/4-trans stereochemistry, the isoxazolidin-4-ols 5a–c were first oxidized to the corresponding ketones

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

• rearrangement of the so-formed alkynyloxiranyl borates. This stereospecific process overall transfers the cis or trans-stereochemistry of the starting alkynyloxiranes to the resulting 1,3-enynes. Keywords: boron; enyne; lithium; oxirane; rearrangement; Introduction Lithiated oxiranes are useful intermediates

• been demonstrated that solvent, oxirane substituent’s nature and of course temperature play key roles [34], in addition to the initial cis or trans stereochemistry, if present [35]. In our case, the oxiranyllithium derived from cis-alkynyloxiranes are configurationally stable as it was established by

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• alkylating agent, which leads to the improved diastereoselectivity [43]. The trans stereochemistry assignment for the dialkylated products 34 follow from the observed equivalence of the acetonide methyl groups in all their proton and carbon NMR spectra. In Seebach's original studies, which established

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

• minor cycloadducts. The trans stereochemistry of the isoxazolidine ring in 72 was the consequence of the endo and exo additions to the Z- and E-nitrones, respectively [80]. Further steps to the orthogonally protected (2S,4S)-73 required selective hydrolysis of the chiral auxiliary, installation of the

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• . The reaction is totally diastereoselective and gives access to the nitrogenated tricyclic core with a relative trans stereochemistry. Keywords: sodium dodecyl sulfate; totally diastereoselective; trans-stereochemistry; Introduction Tricyclic compounds, such as imidazo[2,1-a]isoindol-5-ones, are

cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

• Dimpee Gogoi,
• Runjun Devi,
• Pallab Pahari,
• Bipul Sarma and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2016, 12, 2816–2822, doi:10.3762/bjoc.12.280

• been reductively removed by a diastereoselective method which should be useful in future for preparing libraries of chroman-fused tetralins with trans-stereochemistry at the ring junction. Keywords: brazilin; chroman; epoxy-arene cyclization; natural-product-like molecules; tetralin; Findings The

• that the [6,5]-ring system in brazilin and related natural products 1–4 remains cis-fused, its corresponding [6,6]-ring system in 5 can have cis or trans stereochemistry at the ring junction. In our previous work, we observed a cis relationship (both in concerted or/and stepwise-epoxide ring opening

• by comparison with reported data of related tetracyclic molecules [30][31][32]. Such a stereoselective reductive removal of an –OH group should be useful in preparing a library of chroman-fused tetralins with trans-stereochemistry at the ring junction. Conclusion In conclusion, we herein report a

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

• Rudolf Knorr,
• David S. Stephenson,
• Ernst Lattke,
• Petra Böhrer and
• Jakob Ruhdorfer

Beilstein J. Org. Chem. 2016, 12, 1178–1184, doi:10.3762/bjoc.12.113

• -bromo-1,1-dimethylindene. Keywords: base-free dehydrobromination; cis/trans stereochemistry; five-membered ring conformation; indenes; NMR couplings; Introduction The basic mechanistic features of competing suprafacial and antarafacial additions of elemental bromine to an olefin are reasonably well

Towards stereochemical control: A short formal enantioselective total synthesis of pumiliotoxins 251D and 237A

• Jie Zhang,
• Hong-Kui Zhang and
• Pei-Qiang Huang

Beilstein J. Org. Chem. 2013, 9, 2358–2366, doi:10.3762/bjoc.9.271

• gave pure diastereomer 18 in 59% overall yield from 14. The trans-stereochemistry was tentatively assigned to compound 18 on the basis of our previous results, which was confirmed by the conversion of 18 into the known compound 5 (vide infra). With lactam 18 in hand, its conversion to novel tertiary

Asymmetric synthesis of γ-chloro-α,β-diamino- and β,γ-aziridino-α-aminoacylpyrrolidines and -piperidines via stereoselective Mannich-type additions of N-(diphenylmethylene)glycinamides across α-chloro-N-sulfinylimines

• Gert Callebaut,
• Sven Mangelinckx,
• Pieter Van der Veken,
• Karl W. Törnroos,
• Koen Augustyns and
• Norbert De Kimpe

Beilstein J. Org. Chem. 2012, 8, 2124–2131, doi:10.3762/bjoc.8.239

• , comparable non-halogenated trans-imidazolidines were already synthesized by 1,3-dipolar cycloaddition of N-benzylidene glycine ester enolates across N-sulfinylaldimines in the presence of a Lewis acid [43]. The trans-stereochemistry of imidazolidine 12b was ensured by the vicinal coupling constant 3JH4-H5

Two-directional synthesis as a tool for diversity-oriented synthesis: Synthesis of alkaloid scaffolds

• Kieron M. G. O’Connell,
• Monica Díaz-Gavilán,
• Warren R. J. D. Galloway and
• David R. Spring

Beilstein J. Org. Chem. 2012, 8, 850–860, doi:10.3762/bjoc.8.95

• a single transformation, and also because the all-cis-stereochemistry of 10, which differs from the cis–trans-stereochemistry observed by Stockman for the Dieckman cyclisation of trans-8. For these reasons, further investigations into the process were carried out. The amount of AlCl3 was increased

Perhydroazulene-based liquid-crystalline materials with smectic phases

• Zakir Hussain,
• Henning Hopf and
• S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 403–410, doi:10.3762/bjoc.8.44

• introduction of relevant terminal groups into the isomer that can provide the material with trans-stereochemistry, the resulting derivatives could reveal mesogenic behavior as expected (Figure 1). In the present contribution, we report on the synthesis and mesogenic properties of materials containing a

• /z (%): 471 (6) [M+], 276 (86) [M+ − C13H9NO], 249 (50) [276 − CO], 135 (56) [249 − C8H18], 109 (57) [135 − C2H2], 95 (100) [109 − CH2]; HRMS: calcd for C32H41NO2, 471.313726; found, 471.313482 ± 0.52 ppm. Overall molecular structure of the perhydroazulene core with trans-stereochemistry

α,β-Aziridinylphosphonates by lithium amide-induced phosphonyl migration from nitrogen to carbon in terminal aziridines

• David. M. Hodgson and
• Zhaoqing Xu

Beilstein J. Org. Chem. 2010, 6, 978–983, doi:10.3762/bjoc.6.110

• ) [31][32]. Generation of trans-stereochemistry was also observed in the corresponding N-Boc system [12][15] (see earlier discussion), and the present transformation likely follows a similar reaction pathway: initial trans α-lithiation, which is probably assisted by prior complexation of the base with

Knorr- Rabe partial reduction of pyrroles: Application to the synthesis of indolizidine alkaloids

• Brendon S. Gourlay,
• John H. Ryan and
• Jason A. Smith

Beilstein J. Org. Chem. 2008, 4, No. 3, doi:10.1186/1860-5397-4-3

• occur on the same side as the C-5 substituent, which results in the trans stereochemistry between C-5 and C-8a. A beneficial outcome from these observations is that one can now reduce bicyclic intermediates like 18 stereoselectively to enter either diastereomeric series. Corvo has reported the synthesis