Total synthesis of (+)-grandiamide D, dasyclamide and gigantamide A from a Baylis–Hillman adduct: A unified biomimetic approach

• Andivelu Ilangovan and
• Shanmugasundar Saravanakumar

Beilstein J. Org. Chem. 2014, 10, 127–133, doi:10.3762/bjoc.10.9

• enantiomeric purity of (+)-grandiamide D (5) was found to be 98.6%, as determined from chiral HPLC analysis. (observed [α]D25 = +4.7 (c 0.5, CHCl3); reported [7] [α]D20 = +2.0 (c 0.5, CHCl3). Synthesis of dasyclamide Since Baylis–Hillman adduct (±)-18 was considered as the common intermediate, we decided to

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• the highest enantiomeric purity possible to be competitive with syntheses from enantiomerically pure natural products. n-Propyl and isopropyl esters 21 and 22 were prepared (0.5 mol scale) to moderate the volatility of intermediates, while retaining the option of distillation as a method of

• single peak in a high level of detail despite the often cluttered nature of 1H (and 13C) NMR spectra, especially with large or complex structures. NMR determination of enantiomeric purity using chiral solvents though less well known has been described in the literature [32] and is particularly effective

A protecting group-free synthesis of the Colorado potato beetle pheromone

• Zhongtao Wu,
• Manuel Jäger,
• Jeffrey Buter and
• Adriaan J. Minnaard

Beilstein J. Org. Chem. 2013, 9, 2374–2377, doi:10.3762/bjoc.9.273

• , oxidation and stereoselective methylation using organometallic reagents are the key steps, affording (S)-1 in high enantiomeric purity and in gram quantities. In all these approaches, however, protection of the primary hydroxy group of the 1,2,3-triol substructure is required for the selective oxidation of

Synthesis of axially chiral gold complexes and their applications in asymmetric catalyses

• Yin-wei Sun,
• Qin Xu and
• Min Shi

Beilstein J. Org. Chem. 2013, 9, 2224–2232, doi:10.3762/bjoc.9.261

• stirred at 85 °C for 36 h. Column chromatography of the reaction mixture gave the desired product. The enantiomeric purity of the product was determined by chiral HPLC analysis. Compound 25: 1H NMR (400 MHz, CDCl3, TMS) δ 7.61 (d, J = 8.0 Hz, 2H, ArH), 7.27–7.09 (m, 12H, ArH), 4.17 (d, J = 10.4 Hz, 1H

Synthesis of the calcilytic ligand NPS 2143

• Henrik Johansson,
• Thomas Cailly,
• Alex Rojas Bie Thomsen,
• Hans Bräuner-Osborne and
• Daniel Sejer Pedersen

Beilstein J. Org. Chem. 2013, 9, 1383–1387, doi:10.3762/bjoc.9.154

• disclose for the first time a complete experimental description, detailed characterisation and assessment of enantiomeric purity for (R)-3. An efficient, reproducible and scalable synthesis of (R)-3 that requires a minimum of chromatographic purification steps is presented. (R)-3 was obtained in excellent

Preparation of optically active bicyclodihydrosiloles by a radical cascade reaction

• Koichiro Miyazaki,
• Yu Yamane,
• Ryuichiro Yo,
• Hidemitsu Uno and
• Akio Kamimura

Beilstein J. Org. Chem. 2013, 9, 1326–1332, doi:10.3762/bjoc.9.149

• -Butyl 3-phenyl-2-tosyl-5,5-bis(trimethylsilyl)-1,2,3,3a,4,5-hexahydrosilolo[3,4-c]pyrrole-3a-carboxylate (trans-2a). White solid; mp 144–145 °C; [α]D −31.8 (c 0.68, CHCl3); the enantiomeric purity was determined by HPLC analysis, tR 10.0 min (major), tR 11.5 min (minor) [CHIRALPAK ID (0.46 cm × 25 cm

A versatile and efficient approach for the synthesis of chiral 1,3-nitroamines and 1,3-diamines via conjugate addition to new (S,E)-γ-aminated nitroalkenes derived from L-α-amino acids

• Vera Lúcia Patrocinio Pereira,
• André Luiz da Silva Moura,
• Daniel Pais Pires Vieira,
• Leandro Lara de Carvalho,
• Eliz Regina Bueno Torres and
• Jeronimo da Silva Costa

Beilstein J. Org. Chem. 2013, 9, 832–837, doi:10.3762/bjoc.9.95

• freezer or even at room temperature for several months without decomposition occurring. In order to verify the enantiomeric purity of the new nitroalkenes 2a–c and to confirm their stereochemical stability, a chiral HPLC analysis was conducted. Racemic (+/−)-2b was synthesized from (D/L)-phenylalanine by

• reactive nitroalkenes [15][85][86]. As a way of testing the stereochemical stability of the synthesized nitroalkenes in reaction media, 2b was recovered before the reaction was completed (Table 1, entry 3) and the magnitude of the optical rotation of 2b was measured. No loss in enantiomeric purity of 2b

Inter- and intramolecular enantioselective carbolithiation reactions

• Asier Gómez-SanJuan,
• Nuria Sotomayor and
• Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

• for lithium, leading to (R)-3-methylindoline (R)-46 in 70% ee [47]. This type of intramolecular carbolithiation is also useful for the synthesis of fused furan systems. Thus, enantiomerically enriched 2,3-dihydrobenzofurans 48 are obtained in moderate to good yields and high enantiomeric purity by

Automated three-component synthesis of a library of γ-lactams

• Erik Fenster,
• David Hill,
• Oliver Reiser and
• Jeffrey Aubé

Beilstein J. Org. Chem. 2012, 8, 1804–1813, doi:10.3762/bjoc.8.206

• %) observable in the 13C NMR spectra of the final products (Supporting Information File 1). Such products were deemed suitable for screening purposes. Finally, enantiomeric purity measurements were obtained for six selected γ-lactam products, which ranged between 62 and 84% es. Overall, the results of the

Asymmetric desymmetrization of meso-diols by C₂-symmetric chiral 4-pyrrolidinopyridines

• Hartmut Schedel,
• Keizo Kan,
• Yoshihiro Ueda,
• Kenji Mishiro,
• Keisuke Yoshida,
• Takumi Furuta and
• Takeo Kawabata

Beilstein J. Org. Chem. 2012, 8, 1778–1787, doi:10.3762/bjoc.8.203

• acylpyridinium ion A, and b) the calculated structure of A. Asymmetric desymmetrization of 5 with catalyst 3. Preparation of a small library of chiral C2-symmetric PPY catalysts (reference, see [12]). Amplification of enantiomeric purity of the major enantiomer produced at the step of asymmetric desymmetrization

Organocatalytic asymmetric addition of malonates to unsaturated 1,4-diketones

• Sergei Žari,
• Tiiu Kailas,
• Marina Kudrjashova,
• Mario Öeren,
• Ivar Järving,
• Toomas Tamm,
• Margus Lopp and
• Tõnis Kanger

Beilstein J. Org. Chem. 2012, 8, 1452–1457, doi:10.3762/bjoc.8.165

• catalyst IX, all of the reactions became sluggish at room temperature (Table 3, entries 5, 8, 11 and 14). The reaction times were unreasonably long and the yields remained low. However, in the case of reactions with electron-withdrawing groups, the enantiomeric purity of the products was higher (Table 3

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles

• Pavol Jakubec,
• Dane M. Cockfield,
• Madeleine Helliwell,
• James Raftery and
• Darren J. Dixon

Beilstein J. Org. Chem. 2012, 8, 567–578, doi:10.3762/bjoc.8.64

• but with the intention of targeting a piperidin-2-one ring-containing polycyclic scaffold, cyclic imine 5a was added at the second stage. Tetracyclic spiro-lactam 2a was isolated in high enantiomeric purity (90% ee) in good chemical yield (62%, Scheme 8) [111][112]. For the products of the nitro

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• were achieved for the second step (17–35%) the corresponding acetate was obtained in high enantiomeric purity (ca. 99%). b) Biocatalysts immobilized in ionic liquids (ILs) The discovery of the possibility to immobilize biocatalysts in ionic-liquid phases has been a recent breakthrough that can be

Synthesis of enantiomerically enriched (R)-¹³C-labelled 2-aminoisobutyric acid (Aib) by conformational memory in the alkylation of a derivative of L-alanine

• Stephen P. Fletcher,
• Jordi Solà,
• Dean Holt,
• Robert A. Brown and
• Jonathan Clayden

Beilstein J. Org. Chem. 2011, 7, 1304–1309, doi:10.3762/bjoc.7.152

• amino acids was used to introduce a 13C label into one of the two enantiotopic methyl groups of 2-aminoisobutyric acid (Aib) by retentive alkylation of L-alanine with 13CH3I. Conditions were identified for optimization of yield and enantiomeric purity, and the absolute configuration of the labelled

• % yield from 3. The 1H spectrum of 6* in CD3OD consisted of a 3H CO2Me singlet at 3.85 ppm, plus two coincident signals centred on 1.47 ppm: A 3H doublet (3JHC = 4.3 Hz) for the unlabelled Me, and a 3H doublet (1JHC = 130 Hz) for the labelled Me. The enantiomeric purity of the products was quantified by

• ratio of diastereoisomeric isotopomers. Portion of 13C NMR spectrum of 8 showing location of 13C label in the less shielded methyl group. Portion of 1H NMR spectrum of 8 showing greater 1JHC coupling in the less shielded methyl group. Alkylation of L-alanine. Determining enantiomeric purity and absolute

Single enantiomer synthesis of α-(trifluoromethyl)-β-lactam

• Václav Jurčík,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2011, 7, 759–766, doi:10.3762/bjoc.7.86

• benzylic cleavage. Enantiomeric purity analysis of the resultant β-lactam 1 was evaluated by 19F NMR using a europium chiral shift reagent [Eu(hfc)3]. The comparison of a racemic sample of 1 and then a sample after diastereoisomer separation of 5b as described above, indicated that β-lactam 1 was prepared

Complete transfer of chirality in an intramolecular, thermal [2 + 2] cycloaddition of allene-ynes to form non-racemic spirooxindoles

• Kay M. Brummond and
• Joshua M. Osbourn

Beilstein J. Org. Chem. 2011, 7, 601–605, doi:10.3762/bjoc.7.70

• provided the propargyl acetate 7 in quantitative yield (Scheme 2). The enantiomeric purity of propargyl acetate 7 was determined based on treatment of the compound with the chiral shift reagent (+)-Eu(hfc)3. Figure 1 shows the 1H NMR of the racemic as well as the enantiomerically enriched propargyl acetate

Asymmetric synthesis of tertiary thiols and thioethers

• Jonathan Clayden and
• Paul MacLellan

Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68

• product 6 (Scheme 2). The low yields can be attributed to the formation of β-phenylthioesters 7 by elimination followed by conjugate addition. Even in the presence of the adjacent carbonyl group, competing SN1 dissociation of the benzylic leaving group leads to a loss of enantiomeric purity in some cases

• a variety of thiols to a range of nitroalkenes 49 proceeds to give 50 and hence 51 in good yield and good enantioselectivity (Scheme 19). α-Arylthio-β-amino acid 54 was prepared from Michael adduct 52 in three steps (Scheme 20) in good yield and with full conservation of enantiomeric purity. Palomo

• -butyllithium in diethyl ether and TMEDA at −78 °C for 2.5 hours and quenched with MeOD (Scheme 28). Deuterated thiocarbamate 78 was isolated with an enantiomeric ratio of 72:28, indicating almost full conservation of enantiomeric purity and hence demonstrating that the more congested organolithium 80 is now

Synthesis of chiral mono(N-heterocyclic carbene) palladium and gold complexes with a 1,1'-biphenyl scaffold and their applications in catalysis

• Lian-jun Liu,
• Feijun Wang,
• Wenfeng Wang,
• Mei-xin Zhao and
• Min Shi

Beilstein J. Org. Chem. 2011, 7, 555–564, doi:10.3762/bjoc.7.64

• solution of compound 11 (76.6 mg, 0.20 mmol) in DCM (0.6 mL) was added to the resulting solution and the mixture stirred at rt for 36 h. Column chromatography of the reaction mixture gave the desired product. The enantiomeric purity of the product was determined by chiral HPLC analysis. Monodentate NHCs

Towards racemizable chiral organogelators

• Jian Bin Lin,
• Debarshi Dasgupta,
• Seda Cantekin and
• Albertus P. H. J. Schenning

Beilstein J. Org. Chem. 2010, 6, 960–965, doi:10.3762/bjoc.6.107

• , samples were collected over time and the enantiomeric purity was measured. Racemization was not observed in the gel state (5 mM) after 18 hours, whilst after heating and cooling precipitation was observed. At a concentration of 1 mM, where self-assembled fibers are present, the ee of the solution

Chiral amplification in a cyanobiphenyl nematic liquid crystal doped with helicene-like derivatives

• Alberta Ferrarini,
• Silvia Pieraccini,
• Stefano Masiero and
• Gian Piero Spada

Beilstein J. Org. Chem. 2009, 5, No. 50, doi:10.3762/bjoc.5.50

• and magnitude of the pitch of the cholesteric helix depend on the structure, concentration, and enantiomeric purity of the dopant. Enantiomeric pairs induce oppositely handed cholesteric phases. At low concentration, the helix pitch is inversely proportional to the molar fraction of the dopant; the

Large- scale ruthenium- and enzyme- catalyzed dynamic kinetic resolution of (rac)-1-phenylethanol

• Krisztián Bogár,
• Belén Martín-Matute and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2007, 3, No. 50, doi:10.1186/1860-5397-3-50

• mixture afforded enantiopure acetate 3 in 97% yield after 20 h. Careful analysis of the enantiomeric purity of acetate 3 revealed that it was >99.8% ee. This result is remarkable since only a very low catalyst loading is employed and in addition, only 150 mL of toluene as the solvent is used to produce

An asymmetric synthesis of all stereoisomers of piclavines A1-4 using an iterative asymmetric dihydroxylation

• Yukako Saito,
• Naoki Okamoto and
• Hiroki Takahata

Beilstein J. Org. Chem. 2007, 3, No. 37, doi:10.1186/1860-5397-3-37

• -4 with high enantiomeric purity (amplification) for the major diastereomer via iterative AD reaction of terminal olefins. [8] Results Actually we developed a general access to 5-substituted indolizidines 10 (all four stereoisomers of indolizidine 209D) with high enantio-enhancement (92–98% ee) via a

A convenient allylsilane- N-acyliminium route toward indolizidine and quinolizidine alkaloids

• Roland Remuson

Beilstein J. Org. Chem. 2007, 3, No. 32, doi:10.1186/1860-5397-3-32

• conditions led to a 7:3 mixture of the two diastereomeric alkaloids (+)-myrtine and (-)-epimyrtine. These alkaloids were obtained in five steps from (S)-2-(2-hydroxypropyl)allylsilane 32 with an overall yield of 23% and a high enantiomeric purity. This synthesis constitutes the first total synthesis of

• cyclisation of N-acyliminium ion (S)-49. (-)-Lasubine I and (-)-lasubine II were obtained in six steps with overall yields of 7 and 14% respectively. (+)-Subcosine was prepared in seven steps with an overall yield of 9%. These three compounds were obtained with high enantiomeric purity. These results

Chiral trimethylsilylated C₂-symmetrical diamines as phosphorous derivatizing agents for the determination of the enantiomeric excess of chiral alcohols by ¹H NMR

• Anne-Sophie Chauvin and
• Alexandre Alexakis

Beilstein J. Org. Chem. 2006, 2, No. 6, doi:10.1186/1860-5397-2-6

• derivatising agents, prepared from C2 symmetric trimethylsilylated diamines, for the 1H NMR and 31P NMR determination of the enantiomeric composition of chiral alcohols is described. Introduction NMR spectroscopy is one of the most frequently employed methods used for determining the enantiomeric purity of

Stereoselective α-fluoroamide and α-fluoro- γ-lactone synthesis by an asymmetric zwitterionic aza-Claisen rearrangement

• Kenny Tenza,
• Julian S. Northen,
• David O'Hagan and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2005, 1, No. 13, doi:10.1186/1860-5397-1-13

• reagents, either using asymmetric enolates, [3][4] asymmetric fluorinating reagents[5][6] or asymmetric Lewis acids.[7][8][9] Most recently organocatalysis mediated asymmetric fluorinations have been explored[10] and this has resulted in the efficient preparation of α-fluoroaldehydes in high enantiomeric

• purity.[11] Successes in this area has advanced methodology in organofluorine chemistry considerably over the last decade or so.[1][2] In this paper we explore an alternative approach for the preparation of α-fluorocarbonyls using an asymmetric zwitterionic aza-Claisen rearrangement on appropriate