Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part II: Iridomyrmecins

• Robert Hilgraf,
• Nicole Zimmermann,
• Lutz Lehmann,
• Armin Tröger and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1256–1264, doi:10.3762/bjoc.8.141

• (4S,4aR,7S,7aR)-iridomyrmecin of 95–97% ee and stereochemically pure (4S,4aS,7R,7aS)-iridomyrmecin as a minor component. Keywords: Alloxysta victrix; identification; iridoid; stereoselective synthesis; trans-fused iridomyrmecin; Introduction In the course of our studies on volatile signals of the

• targets in stereoselective synthesis. Similar to dihydronepetalactones, the iridomyrmecin skeleton shows four contiguous stereogenic centers giving rise to four trans-fused stereoisomers A–D and four corresponding enantiomers A'–D' (Figure 3, D' is identical to 2 in Figure 1). The presence of the four

• chiral centers complicates a stereoselective synthesis despite the small size of the molecule. Several methods have been published for the preparation of optically active cis-fused bicyclic iridoid lactones [7][8][9][10], whereas only a few syntheses of trans-fused ring systems have been reported [11

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• intermediate, the stereoselective synthesis of all eight stereoisomers could be achieved (Figure 5). The aldehyde 15 could be readily prepared from commercially available pure and cheap (R)-limonene (14) [25][26][27]. Non-selective hydroboration of the double bond in the side chain of 15 would yield a pair of

• released by the endohyperparasitoid wasp Alloxysta victrix contain the enantiomerically pure trans-fused (4R,4aR,7R,7aS)-dihydronepetalactone as a minor component, showing an unusual (R)-configured stereogenic center at position 7. Keywords: Alloxysta victrix; identification; iridoid; stereoselective

• synthesis; trans-fused dihydronepetalactone; Introduction The endohyperparasitoid wasp Alloxysta victrix is part of the tetratrophic system of oat plants (Avena sativa), grain aphids (Sitobion avenae), primary parasitoids (Aphidius uzbekistanicus) and hyperparasitoids (Alloxysta victrix). Chemical

Synthesis of 2,6-disubstituted tetrahydroazulene derivatives

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

Beilstein J. Org. Chem. 2012, 8, 693–698, doi:10.3762/bjoc.8.77

• ; ring expansion; Introduction Hydroazulene skeletons provide the basic ring systems of natural products, such as guaianolide sesquiterpenes [1][2] and the so-called furanether B series [3][4]. The stereoselective synthesis of trans-hydroazulene derivatives by a tandem Michael/intramolecular Wittig

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

• /bjoc.8.64 Abstract A versatile nitro-Mannich/lactamisation cascade for the direct stereoselective synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles has been developed. A highly enantioenriched substituted 5-nitropiperidin-2-one was synthesised in a four component one-pot

Electrochemical generation of 2,3-oxazolidinone glycosyl triflates as an intermediate for stereoselective glycosylation

• Toshiki Nokami,
• Akito Shibuya,
• Yoshihiro Saigusa,
• Shino Manabe,
• Yukishige Ito and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2012, 8, 456–460, doi:10.3762/bjoc.8.52

• amino sugars [7][8], the selectivity highly depends on the nature of the glycosyl acceptors and reaction conditions. In the last decade, 2,3-oxazolidinone protected 2-amino-2-deoxy-glycosides have been developed as glycosyl donors for the stereoselective synthesis of amino sugars [9][10][11][12][13][14

Synthesis in the glycosciences II

• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2012, 8, 411–412, doi:10.3762/bjoc.8.45

• . Expertise and rational planning have allowed the utilization of carbohydrates in stereoselective synthesis and the employment of enzymes in oligosaccharide synthesis. Analytical and pharmacological knowhow have disclosed polysaccharide and glycoconjugate structures, their biological effects and their

N-Heterocyclic carbene/Brønsted acid cooperative catalysis as a powerful tool in organic synthesis

• Rob De Vreese and
• Matthias D’hooghe

Beilstein J. Org. Chem. 2012, 8, 398–402, doi:10.3762/bjoc.8.43

• (NHCs) has provided a window of opportunities for the development of novel catalytic strategies within the past few years. The recent successful combination of Brønsted acids with NHCs has added a new dimension to the field of cooperative catalysis, enabling the stereoselective synthesis of

• as electrophiles could not be excluded in advance [16]. Application of this methodology indeed enabled the facile and stereoselective synthesis of trans-γ-lactams 16 in a straightforward manner (Scheme 5), which would not have been possible without cooperative catalysis. In a first attempt, this

Efficient, highly diastereoselective MS 4 Å-promoted one-pot, three-component synthesis of 2,6-disubstituted-4-tosyloxytetrahydropyrans via Prins cyclization

• Naseem Ahmed and
• Naveen Kumar Konduru

Beilstein J. Org. Chem. 2012, 8, 177–185, doi:10.3762/bjoc.8.19

• , economical and stereoselective synthesis. To introduce the desired substituents and stereochemistry at the 2, 4 and 6-positions of the tetrahydropyran ring, Prins cyclization has been considered to be the best approach. The reaction can be conducted either with Brønsted acid catalysts – namely TFA [12], AcOH

Synthesis of 2-amino-3-arylpropan-1-ols and 1-(2,3-diaminopropyl)-1,2,3-triazoles and evaluation of their antimalarial activity

• Matthias D’hooghe,
• Stéphanie Vandekerckhove,
• Karen Mollet,
• Karel Vervisch,
• Stijn Dekeukeleire,
• Liesbeth Lehoucq,
• Carmen Lategan,
• Peter J. Smith,
• Kelly Chibale and
• Norbert De Kimpe

Beilstein J. Org. Chem. 2011, 7, 1745–1752, doi:10.3762/bjoc.7.205

• efforts have been devoted to the preparation of structurally diverse analogues bearing a functionalized propane skeleton [6][7][8]. In that respect, we have been engaged in the stereoselective synthesis of syn-2-alkoxy-3-amino-3-arylpropan-1-ols 1 by reductive ring opening of the corresponding β-lactams

• stereoselective synthesis of functionalized aminopropanols. In accordance with a literature approach [30], the nonactivated trans-2-aryl-3-(hydroxymethyl)aziridines 7 were regio- and stereoselectively converted into anti-2-amino-3-aryl-3-methoxypropan-1-ols 8a–e through heating in methanol under reflux (Scheme 1

Tertiary alcohol preferred: Hydroxylation of trans-3-methyl-L-proline with proline hydroxylases

• Christian Klein and
• Wolfgang Hüttel

Beilstein J. Org. Chem. 2011, 7, 1643–1647, doi:10.3762/bjoc.7.193

• Enantiomerically pure tertiary alcohols are valuable building blocks for the synthesis of natural products, biologically active compounds, and pharmaceuticals. However, their stereoselective synthesis is often challenging, as the reaction centers are sterically hindered or electronically disfavored. In addition to

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• -arylation and intramolecular N-arylation (Scheme 29). The palladium-mediated amination reaction coupled with a nitrogen–carbon bond-forming reaction was also used for the stereoselective synthesis of N-aryl-2-benzylpyrrolidines 71 starting from linear 4-pentenylamine and its derivatives [38]. In this tandem

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

• allylic acetates [75][76], carbene-transfer reactions from ethyl diazoacetate [77], formation of conjugated enones and enals [78], regio- and stereoselective synthesis of fluoroalkenes [79], and so on [80][81][82][83][84][85]. However, reports on NHC–Au catalyzed asymmetric reactions are rare [86]. The

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• formation reactions in synthetic organic chemistry have attracted considerable attention in recent years [1]. Palladium-catalyzed allylation is also a particularly useful method for the activation of allylic substrates [2]. Trost et al. described a highly stereoselective synthesis of oxazolidinone 2

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• -1,4-diketones after hydrolysis of the primary photochemical products (photo aldol reaction) [7], whilst the reaction of oxazoles with carbonyl compounds is a convenient protocol for the stereoselective synthesis of α-amino β-hydroxy ketones [8][9] as well as highly substituted α-amino β-hydroxy acids

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• [53]. Intramolecular palladium-catalysed N-arylations have been applied to substituted arenes and thiophenes with good to excellent yields. Electron-rich bromides gave the best results, while pyridine derivatives were unreactive [54]. Another intramolecular approach enabled the stereoselective

• synthesis of an atropisomeric N-(2-tert-butylphenyl)lactam as an intermediate for norepinephrine transporter (NET) inhibitor 16. NET inhibitors were developed to treat a variety of mental disorders such as depression and attention deficit hyperactivity disorder (ADHD). Screening different ligands, SERGPHOS

Stereoselective synthesis of four possible isomers of streptopyrrolidine

• Debendra K. Mohapatra,
• Barla Thirupathi,
• Pragna P. Das and
• Jhillu S. Yadav

Beilstein J. Org. Chem. 2011, 7, 34–39, doi:10.3762/bjoc.7.6

Achiral bis-imine in combination with CoCl₂: A remarkable effect on enantioselectivity of lipase-mediated acetylation of racemic secondary alcohol

• K. Arunkumar,
• M. Appi Reddy,
• T. Sravan Kumar,
• B. Vijaya Kumar,
• K. B. Chandrasekhar,
• P. Rajender Kumar and
• Manojit Pal

Beilstein J. Org. Chem. 2010, 6, 1174–1179, doi:10.3762/bjoc.6.134

• the stereoselective synthesis of chiral molecules have increased enormously in recent years especially in the chemical and pharmaceutical industry [1]. Biocatalysis, being an environmentally friendly process, has attracted particular attention for this purpose [2][3][4][5][6]. For example, high

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• suitable substrates for Lewis-acid induced cyclizations furnishing mono-, di-, or spirocyclic dihydropyrans. Subsequent reactions such as bromination, acidic hydrolysis or dihydroxylation provided differently substituted and configured pyranone derivatives as precursors for the stereoselective synthesis of

Bis(oxazolines) based on glycopyranosides – steric, configurational and conformational influences on stereoselectivity

• Tobias Minuth and
• Mike M. K. Boysen

Beilstein J. Org. Chem. 2010, 6, No. 23, doi:10.3762/bjoc.6.23

• ligands for metal catalysed transformations is of crucial importance for stereoselective synthesis and is therefore an active field of research. In this context, carbohydrates are interesting, even if comparatively rarely used as starting materials for the preparation of new chiral ligand structures

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• antibiotic against Gram-negative organisms, which contains two highly functionalised aminosugars connected by an urea linkage [61]. While exploring the synthesis of this target molecule, this group established a new method for the stereoselective synthesis of novel β-urea-linked pseudooligosaccharides, which

Benzyne arylation of oxathiane glycosyl donors

• Martin A. Fascione and
• W. Bruce Turnbull

Beilstein J. Org. Chem. 2010, 6, No. 19, doi:10.3762/bjoc.6.19

• , carbohydrate chemists must overcome the myriad challenges presented by their complex synthesis. The most important challenge is control over the stereoselectivity of reactions at the anomeric centre; in particular for the stereoselective synthesis of 1,2-cis-glycosides [9]. This area has been the subject of

Synthesis of some novel annulated pyrido[2,3-d]pyrimidines via stereoselective intramolecular hetero Diels–Alder reactions of 1-oxa-1,3-butadienes

• Mohit L. Deb and
• Pulak J. Bhuyan

Beilstein J. Org. Chem. 2010, 6, No. 11, doi:10.3762/bjoc.6.11

• function. Results and Discussion As part of our continued interest in uracils [41][42][43][44][45] and the development of highly expedient methods for the synthesis of diverse heterocyclic compounds of biological importance [46][47][48][49][50], we now report the stereoselective synthesis of some new

• , 15.82. Stereoselective synthesis of some new complex annulated pyrido[2,3-d]pyrimidines by intramolecular hetero Diels–Alder reactions involving 1-oxa-1,3-butadienes. Synthesis of some novel annulated pyrido[2,3-d]pyrimidines 6/7.a Supporting Information Supporting Information File 30: Spectroscopic

Synthesis of (3R,5R)-harzialactone A and its (3R,5S)-isomer

• Gowravaram Sabitha,
• Rangavajjula Srinivas,
• Sukant K. Das and
• Jhillu S. Yadav

Beilstein J. Org. Chem. 2010, 6, No. 8, doi:10.3762/bjoc.6.8

• carbon in the downfield region (100.5 ppm) [7]. In conclusion, a stereoselective synthesis of natural (+)-(3R,5R)-harzialactone A and its nonnatural stereoisomer (3R,5S) has been accomplished. Natural harzialactone A (1), and its (3R,5S)-isomer (2). Retrosynthesis of harzialactone A (1). Synthesis of

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• the indole moiety, this method led to a convenient stereoselective synthesis of a highly substituted pyrroloindole framework 74 (Scheme 30); however, equimolar amounts of triethylborane were necessary. An improved FC allylation of indoles with allyl alcohols was developed recently by Breit et al

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• (in the case of transition metal-catalyzed reactions) also can be problematic in large-scale syntheses, especially in pharmaceutical applications. Consequently, reactions based on the use of supported catalysts are in many ways a more attractive option for the stereoselective synthesis of chiral

• was developed for the reaction of imino esters with ketenes, leading to the stereoselective synthesis of ß-lactams [30]. Ketene was generated from the corresponding acid chloride with polymer-supported BEMP 17, and was reacted with an imino ester in a reaction catalyzed by the resin-supported quinine