A facile, rapid, one-pot regio/stereoselective synthesis of 2-iminothiazolidin-4-ones under solvent/scavenger-free conditions

• Murugan Sathishkumar,
• Sangaraiah Nagarajan,
• Poovan Shanmugavelan,
• Murugan Dinesh and
• Alagusundaram Ponnuswamy

Beilstein J. Org. Chem. 2013, 9, 689–697, doi:10.3762/bjoc.9.78

• obtained. Thus, the present investigation affording a single regioisomeric product exclusively is the first report wherein the allylic strains are noted to direct the high regioselectivity. Finally, the stereoselective formation of the (Z)-stereoisomer is also explicable based on allylic strain, which is

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

• Toshiki Tabuchi,
• Daisuke Urabe and
• Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

• to 3.4:1 by replacement of the solvent (Table 1, entries 4 and 5). Thus, we developed an effective method for synthesis of the requisite stereoisomer 8 by applying a TBSOTf-promoted Diels–Alder reaction [25][26]. Most importantly, the C4-stereocenter behaved as the control element to introduce the

• afforded 22 as a single stereoisomer, and the obtained 22 was oxidized with DMDO to provide α-hydroxy aldehyde 23 as a diastereomeric mixture (dr = 2.8:1). Compound 23 then reacted with benzyl hydroxylamine to produce oxime 24, LiAlH4-treatment of which led to 25. The regioselective ring expansion of seven

Some aspects of radical chemistry in the assembly of complex molecular architectures

• Béatrice Quiclet-Sire and
• Samir Z. Zard

Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61

• replaced with various primary amines, one example being cyclopropylamine, which furnishes piperidine 129 as one stereoisomer. In the case of 1,2-diaminoethane, a further cyclisation is observed leading to bicyclic piperidine 130. All three components involved in this modular approach can be modified to

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

• Andrew Tigchelaar and
• William Tam

Beilstein J. Org. Chem. 2012, 8, 1765–1770, doi:10.3762/bjoc.8.201

• single stereoisomer was formed, with the H at the ring junction and the R group anti to each other. The stereochemistry of the cycloadducts was assigned by comparison with spectral data from previous work. This stereochemistry is consistent with that of previously reported intramolecular [4 + 2

trans-2-(2,5-Dimethoxy-4-iodophenyl)cyclopropylamine and trans-2-(2,5-dimethoxy-4-bromophenyl)cyclopropylamine as potent agonists for the 5-HT₂ receptor family

• Adam Pigott,
• Stewart Frescas,
• John D. McCorvy,
• Xi-Ping Huang,
• Bryan L. Roth and
• David E. Nichols

Beilstein J. Org. Chem. 2012, 8, 1705–1709, doi:10.3762/bjoc.8.194

• successful in leading to compounds with high affinity at the 5-HT2 family of receptors; and the more potent stereoisomer of the cyclopropane analogues had the expected (−)-(1R,2S)-configuration. Screening for affinity at various serotonin receptor subtypes, however, revealed that the cyclopropane congeners

• in leading to compounds with high affinity at the 5-HT2 family of receptors; and the more potent stereoisomer of the cyclopropane analogues had the expected (−)-1R,2S-configuration. However, at appropriate doses, although (−)-4 and (−)-5 may be useful as tools to probe 5-HT2 receptor function, one

The preferred conformation of erythro- and threo-1,2-difluorocyclododecanes

• Yi Wang,
• Peer Kirsch,
• Tomas Lebl,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2012, 8, 1271–1278, doi:10.3762/bjoc.8.143

• hyperconjugative interactions with the anti-periplanar C–H bonds, similar to that found in 1,2-difluoroethane in the well know gauche effect [10][11]. On the other hand, the erythro stereoisomer 5a would have a C–F bond projecting into the ring in an endo manner, if the vicinal fluorines were edge/edge located

• . The structures and relative energies for the erythro 5a and threo 5b isomers are shown in Figure 6. These data indicate that the corner/edge conformers are more stable than the alternative edge/edge conformers for each stereoisomer. This is consistent with the conclusions from the experimental VT 19F

• NMR study. For the erythro stereoisomer 5a, three conformers I–III were considered. Conformers I and II each have a fluorine pointing into the ring (endo), and thus there is an increase in transannular ring strain, raising the energy of these conformers by 2.81 and 3.72 kcal·mol−1 respectively above

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

• ]. Actually, 18 was first identified in the defensive secretions of dolichoderine ants [25]. The same substance (or its enantiomer) has been found as a defensive compound of Nematine larvae [30] and in adults and larvae of the thrips Calloccithrips fuscipennis [31]. A stereoisomer of dolichodial

• – anisomorphal (19) – is a component of the defensive secretion of the walking stick Anisomorpha buprestoides [32], whilst a third stereoisomer – peruphasmal (20) – has been identified in another walking stick, Peruphasma schultei [33][34]. Recent investigations show that the qualitative and quantitative

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

• upon intramolecular aldol condensation [25][26][27]. Subsequently, the aldehyde 15 was reduced to the allylic alcohol 19 with LiAlH4 and converted into the acetate 20 [28]. Hydroboration of 20 using disiamylborane proceeded with high stereoselectivity affording 16 as a single stereoisomer [17][28

Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step

• Dieter Enders,
• Jeanne Fronert,
• Tom Bisschops and
• Florian Boeck

Beilstein J. Org. Chem. 2012, 8, 1112–1117, doi:10.3762/bjoc.8.123

• ), the (S)-proline catalyzed 5-enolexo aldol key step of this synthesis could be performed in good yield (71%). To our delight, we found in this case an exceedingly high diastereo- (99%) and enantioselectivity (99%) for the aldol reaction, furnishing the aldol product 14 as a single stereoisomer. The

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• define a specific orientation or conformation of each stereoisomer (trans or cis). Recently, Carreño et al. [132][133] synthesized different enantiomerically pure sulfinyl azobenzenes. The sulfinyl group is a key component in the design of a molecular sunflower, a device that by means of light can

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

• compound(s) was found to give a mixture of stereoisomers. However, in the present case, we were only able to isolate 4 as a single stereoisomer. Furthermore, the procedure for the synthesis of compounds 4 and 5 is essentially the same as described previously for analogous compounds [10]. The complete

An easy α-glycosylation methodology for the synthesis and stereochemistry of mycoplasma α-glycolipid antigens

• Yoshihiro Nishida,
• Yuko Shingu,
• Yuan Mengfei,
• Kazuo Fukuda,
• Hirofumi Dohi,
• Sachie Matsuda and
• Kazuhiro Matsuda

Beilstein J. Org. Chem. 2012, 8, 629–639, doi:10.3762/bjoc.8.70

• conformation. Here, it should be mentioned that the conformer distribution coincides between I-a (Figure 3, entry 5) and DPPC (Figure 3, entry 2) at the head moiety [gt (33%), gg (34%) and tg (33%)]. The above analysis was carried out also for the stereoisomer I-b and the related glycolipids (Figure 4, entries

• conformer in I-b is reversed (anticlockwise) from the case of DPPC and GGPL-I (clockwise), as depicted in Figure 3 and Figure 4. Conclusion We have proposed a synthetic pathway to a GGPL-I homologue and its stereoisomer, in which our one-pot α-glycosylation methodology was effectively applied. We envisage

Conserved and species-specific oxylipin pathways in the wound-activated chemical defense of the noninvasive red alga Gracilaria chilensis and the invasive Gracilaria vermiculophylla

• Martin Rempt,
• Florian Weinberger,
• Katharina Grosser and
• Georg Pohnert

Beilstein J. Org. Chem. 2012, 8, 283–289, doi:10.3762/bjoc.8.30

• not be resolved due to the substantial overlap of the signals. An isomer of 5 bearing also a conjugated tetraene unit was isolated and tentatively assigned to a stereoisomer with an E-configured double bond between C11 and C12 and open stereochemistry of the C7/C8 bond. Despite the stereocenter at C4

Synthesis of fused tricyclic amines unsubstituted at the ring-junction positions by a cascade condensation, cyclization, cycloaddition then decarbonylation strategy

• Iain Coldham,
• Adam J. M. Burrell,
• Hélène D. S. Guerrand,
• Luke Watson,
• Nathaniel G. Martin and
• Niall Oram

Beilstein J. Org. Chem. 2012, 8, 107–111, doi:10.3762/bjoc.8.11

• alkene. A single stereoisomer of product 2 was formed. Alternatively, glycine could be used and led to a tricyclic product via an intermediate azomethine ylide formed by decarboxylation. Unfortunately, when the substrate 1 (R = H) was used, heating with glycine or glycine ethyl ester did not yield the

• glycine ethyl ester in toluene gave the desired tricyclic product 13a as the major stereoisomer, together with a small amount of the separable stereosiomer 13b (Scheme 4). The major isomer 13a was assumed to have the all-cis configuration based on related chemistry (compare with product 2 [19][20], Scheme

• glycine in toluene gave the desired tricyclic product 19 as a single stereoisomer. NOESY studies verified the stereochemistry as shown. Only one of the two alkene groups acts as the dienophile, as expected for conformational reasons. This synthesis (six steps from nitrile 3) represents an efficient entry

Synthesis of highly functionalized β-aminocyclopentanecarboxylate stereoisomers by reductive ring opening reaction of isoxazolines

• Melinda Nonn,
• Loránd Kiss,
• Reijo Sillanpää and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2012, 8, 100–106, doi:10.3762/bjoc.8.10

• cispentacin stereoisomer 2 into multifunctionalized β-amino acid derivative 12. Synthesis of multifunctionalized β-amino acid derivatives 13–16. Reaction conditions: NaBH4, NiCl2, Boc2O, EtOH/H2O, rt, 6 h. Acknowledgements We are grateful to the Hungarian Research Foundation (OTKA No. T81371) for financial

Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

• Patrick Claude,
• Christian Lehmann and
• Thomas Ziegler

Beilstein J. Org. Chem. 2011, 7, 1609–1619, doi:10.3762/bjoc.7.189

• canonical stereochemical principles, we do not perceive a clear reason why they should not also cyclize to the α(1→2)-stereoisomer; indeed, extensive MD calculations (>5000 ps) on each of the possible product diastereomers (Figure 7, Figure 8 and Figure 9) converge into most-stable, rearranged product

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

• diastereoisomers of 5b could be separated by careful chromatography over silica gel and this led to the recovery of each isomer as a major and a minor product. Finally, oxidative scission of the major β-lactam stereoisomer (αS,3R)-5b, using CAN was relatively straightforward generating β-lactam (S)-1 in 67% yield

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

• )-7b presumably due to the steric repulsion between the π-allyl group and the acetylated amino group in another phenyl group. However, we were unable to isolate either stereoisomer in a pure form by silica gel column chromatography. After recrystallization from DCM and pentane (1:3), one of the two

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• ). The stereochemistry of the benzylidene acetal 18 formed by this method has been studied by Suzuki et al. who assigned the product as the (7S)-stereoisomer (but reported it as the (7R)-isomer) by observation of a nuclear Overhauser effect transfer between the methine proton of the benzylidene acetal

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• , whereas a 1,2-relationship was observed starting from internal alkynes (Scheme 9) [62][63]. In addition, the stereoselectivity was low in the first case (3:1) and a single regio- and stereoisomer was obtained from internal alkynes. The regioselectivity was proposed to originate from the steric and

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• Grignard from which the organocopper compound was prepared (Scheme 20) [46][47][48][49][50]. Excess of copper salt provides a better stereoisomeric ratio (>90%) [46]. Only the addition of t-BuCu gave a single stereoisomer [51]. In contrast, the copper-catalyzed carbozincation reaction led to a single

• stereoisomer via syn addition under mild conditions in either THF or Et2O (Scheme 20) and the reaction could be expanded to incorporate a large variety of functionalized alkylzinc bromide and dialkylzinc species [52]. Copper-catalyzed carbozincation could also be performed under very different conditions

• (toluene, reflux) and a single isomer was still obtained [53]. 1-Alkynyl sulfoximines behave similarly to alkynyl sulfones and the addition of an organocopper reagent usually leads to two isomers in variable amounts. Copper-catalyzed carbozincation to give a single regio- and stereoisomer in excellent

Prins fluorination cyclisations: Preparation of 4-fluoro-pyran and -piperidine heterocycles

• Guillaume G. Launay,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2010, 6, No. 41, doi:10.3762/bjoc.6.41

• determined and the syn-stereoisomer 9b, as shown in Figure 2, was confirmed as the major product of this Prins reaction. It is interesting to note that when (E)- and (Z)-hex-3-en-1-ol (11a) and (11b) were used as substrates, the double bond stereochemistry is retained. Only two diastereoisomers were observed

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

• . Epoxide opening with thioacetal and diastereoselective reductions are used as key reactions. Keywords: dithiane; harzialactone A; hydroxyl directed reduction; stereoisomer; Introduction Marine microorganisms such as bacteria, fungi, and microalgae have proved to be a rich source of structurally novel

• the major product, which was converted into stereoisomer (3R,5S)-2 via acetonide 12, deprotection of benzyl group to give 13, and further functional group transformations by use of the same reagents and conditions as those described for the conversion of 10 into 1. The IR absorption at 1775 cm−1

• 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

Three step synthesis of single diastereoisomers of the vicinal trifluoro motif

• Vincent A. Brunet,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2009, 5, No. 61, doi:10.3762/bjoc.5.61

• absolute configuration (Figure 1). Generation of the syn-α,β-epoxy alcohols Aa was more challenging. This stereoisomer will ultimately deliver the all-syn Da trifluoro motif (Scheme 1). Epoxidation of (S)-5 with L-DIPT showed poor stereoselectivity and under optimised conditions the resultant α,β-epoxy

• diastereoisomeric series. Reaction of α,β-epoxy alcohol 7b with Deoxo-Fluor® also proceeded smoothly generating fluoro epoxide (2S,3S,4R)-9b in 95% yield and as a single stereoisomer. However when 9b was treated with HF/pyridine [19][20] there was no evidence that the expected difluoro alcohol 12b had formed