The simple production of nonsymmetric quaterpyridines through Kröhnke pyridine synthesis

• Isabelle Sasaki,
• Jean-Claude Daran and
• Gérard Commenges

Beilstein J. Org. Chem. 2015, 11, 1781–1785, doi:10.3762/bjoc.11.193

• of 3.425(1) Å, resulting in a slippage of 1.54 Å. The absolute configuration is established by the occurrence of the known chirality of the starting material as (−)-(1R,5S)-myrtenal was used. Crystals of complex 9 were obtained by slow evaporation of a solution of the compound with

• distorted, square planar environment. The PtN4 framework is nearly planar with the largest deviations being −0.008(4) Å at the Pt atom. However, to accommodate the tetracoordination, the N-Pt-N angles range from 80.3(3)° to 116.8(3)°. Because of the presence of the Pt atom, the absolute configuration can be

Towards inhibitors of glycosyltransferases: A novel approach to the synthesis of 3-acetamido-3-deoxy-D-psicofuranose derivatives

• Maroš Bella,
• Miroslav Koóš and
• Chun-Hung Lin

Beilstein J. Org. Chem. 2015, 11, 1547–1552, doi:10.3762/bjoc.11.170

• (Table 2) are indicative of OT1 conformation (O2TC6, twisted on O2–C6, C6-exo, O2-endo). The absolute configuration at chiral atoms C2, C3, and C4 of the O1–C1–C2–C3–C4 furanose ring (Figure 2) was assigned on the basis of the known arrangement in analogous D-psicofuranose derivatives. The α-D

The enantioselective synthesis of (S)-(+)-mianserin and (S)-(+)-epinastine

• Piotr Roszkowski,
• Jan. K. Maurin and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2015, 11, 1509–1513, doi:10.3762/bjoc.11.164

• solubility in a hexane/2-propanol mixture. The absolute configuration of amine (S)-7 obtained by reduction of 6 using (R,R)-11 as catalyst was confirmed by X-ray analysis (Figure 3). Subsequently, the synthetic procedure developed by us for aptazepine was applied [8]. Amide 8 was obtained in 94% yield by

Chiroptical properties of 1,3-diphenylallene-anchored tetrathiafulvalene and its polymer synthesis

• Masashi Hasegawa,
• Junta Endo,
• Seiya Iwata,
• Toshiaki Shimasaki and
• Yasuhiro Mazaki

Beilstein J. Org. Chem. 2015, 11, 972–979, doi:10.3762/bjoc.11.109

• consistent with the hypothesis from the chiral exciton coupling method. To solidify the absolute configuration, the synthesis of (R)-3 from (R)-9 was carried out separately, and the ECD spectrum of the product from (R)-3 was in complete accord with that of (−)-9. Therefore, the absolute configuration of

• intensive Cotton effects at 318 nm (λfirst) and 254 nm (λsecond), together with a weak ellipticity in the range of ca. 360–450 nm. The shape of the trend line of PTDPA is similar to that of 3 with the same absolute configuration at the allenic moiety except for the small blue shift of the λsecond value of

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

• means of the assignment of the absolute configuration of the resolved enantiopure alcohol (S)-(+)-5 determined by a modified Mosher’s methodology, and was unambiguously confirmed by X-ray diffraction analysis. Optically active intermediates (S)-(+)-5 and (R)-(−)-7 achieved in this manner were

• scale” and ready-to-use for further transformations. Determination of the stereochemistry of alcohol (+)-5 The determination of the absolute configuration is crucial for all chiral molecules, but it is especially important for active pharmaceutical ingredients (APIs) like those presented herein, whereas

• help us to plan further steps of the synthesis. Therefore, the stereopreference of the above-studied lipase preparations was evaluated by means of modified Mosher’s methodology described by Riguera et al. [71] In this relatively simple and widely-used experimental approach, the absolute configuration

Trogopterins A–C: Three new neolignans from feces of Trogopterus xanthipes

• Soyoon Baek,
• Xuikui Xia,
• Byung Sun Min,
• Chanil Park and
• Sang Hee Shim

Beilstein J. Org. Chem. 2014, 10, 2955–2962, doi:10.3762/bjoc.10.313

• different in that it did not contain a methoxy group at the C-4′ position nor an ether linkage between C-4 and C-7′ to form a dihydrofuran ring. The absolute configuration of compound 2 was determined by comparing its optical rotation with those of (R)-2,3-diphenyl-1-propanol and (S)-2,3-diphenyl-1-propanol

(2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-Mono(di,tri)fluoromethylcyclopropyl]alanines and their incorporation into hormaomycin analogues

• Armin de Meijere,
• Sergei I. Kozhushkov,
• Dmitrii S. Yufit,
• Christian Grosse,
• Marcel Kaiser and
• Vitaly A. Raev

Beilstein J. Org. Chem. 2014, 10, 2844–2857, doi:10.3762/bjoc.10.302

• isolated from a Streptomyces griseoflavus (strain W-384) fermentation broth by Zähner et al. in Tübingen, Germany and structurally identified by Zeeck et al. in Göttingen, Germany in 1989–1990 [3][4]. Once the absolute configuration of all the previously unassigned stereogenic centers in the

• . Unfortunately, the diastereomers could not be separated by fractional crystallization as easily as was previously reported for the corresponding 3-(trans-2-nitrocyclopropyl)alanine derivatives [7]. The absolute configuration of the arbitrarily selected nickel(II) complexes (2S,1'R,2'S)-26a, (2S,1'R,2'S)-26b and

• by experimental tests [36]. The initially formed main product (R,R,R)-28 in the aldol reaction of acetaldehyde with 10 had the same configuration at C-2 as the proline unit in 10. The absolute configuration of this nickel(II) complex was determined by a single crystal X-ray structure analysis (see

Aspergiloid I, an unprecedented spirolactone norditerpenoid from the plant-derived endophytic fungus Aspergillus sp. YXf3

• Zhi Kai Guo,
• Rong Wang,
• Wei Huang,
• Xiao Nian Li,
• Rong Jiang,
• Ren Xiang Tan and
• Hui Ming Ge

Beilstein J. Org. Chem. 2014, 10, 2677–2682, doi:10.3762/bjoc.10.282

• derived from Ginkgo biloba. Its structure was unambiguously established by analysis of HRMS–ESI and spectroscopic data, and the absolute configuration was determined by low-temperature (100 K) single crystal X-ray diffraction with Cu Kα radiation. This compound is structurally characterized by a new

Preparation of neuroprotective condensed 1,4-benzoxazepines by regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction

• László Tóth,
• Yan Fu,
• Hai Yan Zhang,
• Attila Mándi,
• Katalin E. Kövér,
• Tünde-Zita Illyés,
• Attila Kiss-Szikszai,
• Balázs Balogh,
• Tibor Kurtán,
• Sándor Antus and
• Péter Mátyus

Beilstein J. Org. Chem. 2014, 10, 2594–2602, doi:10.3762/bjoc.10.272

• ). TDDFT-ECD calculation was proved an efficient method to determine the absolute configuration of separated stereoisomers of bioactive synthetic [19] and natural derivatives [20][21] on the basis of their HPLC-ECD spectra. For the configurational assignment of the separated enantiomers, TDDFT-ECD

• TDDFT-ECD spectra of (2S,15aS)-7d and (2S,15aS)-7b gave good agreement with the experimental HPLC-ECD spectra of the second-eluting enantiomers (Figure 4a,b), which allowed determining the absolute configuration of their second-eluting enantiomers (negative CEs at 370 and 371 nm, respectively) as (2S

De novo macrolide–glycolipid macrolactone hybrids: Synthesis, structure and antibiotic activity of carbohydrate-fused macrocycles

• Richard T. Desmond,
• Anniefer N. Magpusao,
• Chris Lorenc,
• Jeremy B. Alverson,
• Nigel Priestley and
• Mark W. Peczuh

Beilstein J. Org. Chem. 2014, 10, 2215–2221, doi:10.3762/bjoc.10.229

• ring, the presence of rigidifying planar units and stereocenters collectively govern the shape of a given macrocycle. In fact, we observed that the absolute configuration of C4 of the pyranose ring strongly influenced the shape and reactivity of macrocycle 3 [9]. In 3, the oxygens at C4 and C6 are both

• backbone of the macrocycle whose chirality is dictated by the absolute configuration of the C4 stereogenic center. The topology is a defining feature of this family of [13]-macrodiolides. By virtue of the planar chirality, [13]-macrodiolides such as 3 have an axis of chirality associated with them. We were

• this case the macrocyclic ring. In total it is the balancing of a number of small factors such as rigidification by multi-atom planar units, absolute configuration of stereogenic centers and stereoelectronic effects that dictate the observed structures. Minimum inhibitory concentrations (MICs) against

Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds

• Miroslav Palík,
• Jozef Kožíšek,
• Peter Koóš and
• Tibor Gracza

Beilstein J. Org. Chem. 2014, 10, 2077–2086, doi:10.3762/bjoc.10.216

• formed from σ-alkyl PdII-complexes F and G by reductive elimination of Pd0 (Scheme 6). Additionally, the X-ray analysis [44] of 53 confirmed the absolute configuration and structure of the six-membered heterocycle (Figure 4). Recently, Wolfe reported a tetrahydrofuran-forming reaction via Pd-catalysed

Building complex carbon skeletons with ethynyl[2.2]paracyclophanes

• Ina Dix,
• Lidija Bondarenko,
• Peter G. Jones,
• Thomas Oeser and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 2013–2020, doi:10.3762/bjoc.10.209

• diastereomers are generated (as expected) by the oxidative dimerization of the mono ethynyl derivative [9], but assignment of the various spectra to specific stereoisomers remains an open question, and will only be possible after the resolution of the 4-ethynyl[2.2]paracyclophane, determination of its absolute

• configuration, and oxidative dimerization of an enantiopure sample. Glaser coupling of racemic 4 at room temperature yielded a mixture of diastereomeric dimers in good yield (67%) under the conditions shown in Scheme 4. Their gross structures follow from the spectroscopic and analytical data summarized in the

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• ketal under acidic conditions to reveal the ketone moiety and final oxidation of the primary alcohol with tetrapropylammonium perruthenate (TPAP) completed the first enantioselective total synthesis of anthoplalone (8) and confirmed the absolute configuration of the natural product [56][103][104]. PTP

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• %. The diastereoisomers were separated and their absolute configuration was determined using X-ray crystallography and circular dichroism spectroscopy. The stereochemical outcome of the synthesis of compounds 79 and 80 was suggested to result from some internal asymmetric induction of the chiral residue

• under the same conditions. The absolute configuration of the C-4 carbon atom of compound 91 or ent-91 was not determined. The approach involving an enamine (i.e., compound 92) as one of the reaction components was also used by Tewari et al. for the preparation of C-nucleosides 93 (Scheme 37) [111]. The

Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction

• Marina Rubina,
• William M. Sherrill,
• Alexey Yu. Barkov and
• Michael Rubin

Beilstein J. Org. Chem. 2014, 10, 1536–1548, doi:10.3762/bjoc.10.158

• the time when starting material 1 was completely consumed, the entire amount of 3a produced was transformed into 4a (Table 1, entry 5). Remarkably, the absolute configuration at C2 did not change at all through the reaction course; moreover, the optical purity of both products 3a and 4a remained

• sluggishly (Table 2, entries 5 and 6), and allowed for only insignificant improvement in enantioselectivity (84–87% ee). Most remarkably, the same (R)-enantiomer of product 3 was obtained, despite the opposite absolute configuration of L3 with respect to L1 (Figure 3). In other words, switching from Ph to t

• corresponding catalytic systems. We envisioned that inverting the absolute configuration of the asymmetric center at C4 in the dihydrooxazole ring might potentially help to improve the enantioselectivity of the arylation reaction. Indeed, it is reasonable to propose that the inversion of the stereogenic center

Asymmetric Ugi 3CR on isatin-derived ketimine: synthesis of chiral 3,3-disubstituted 3-aminooxindole derivatives

• Giordano Lesma,
• Fiorella Meneghetti,
• Alessandro Sacchetti,
• Mattia Stucchi and
• Alessandra Silvani

Beilstein J. Org. Chem. 2014, 10, 1383–1389, doi:10.3762/bjoc.10.141

• diffraction of the obtained crystal established the absolute configuration S at the tetrasubstituted stereocenter C3, which corresponds to C7a of the arbitrary atom-numbering scheme used (Figure 2). The stereochemical assignment S was attributed on the basis of the known (S)-configuration of the phenyl

Synthesis of 1-[bis(trifluoromethyl)phosphine]-1’-oxazolinylferrocene ligands and their application in regio- and enantioselective Pd-catalyzed allylic alkylation of monosubstituted allyl substrates

• Zeng-Wei Lai,
• Rong-Fei Yang,
• Ke-Yin Ye,
• Hongbin Sun and
• Shu-Li You

Beilstein J. Org. Chem. 2014, 10, 1261–1266, doi:10.3762/bjoc.10.126

• : 96/4, 88% ee, entry 9, Table 1). When the reaction was run at −30 °C, only a trace amount of product was formed. As for the leaving groups of allyl substrates, the cinnamyl acetate could also be tolerated to give a similar level of regio- and enantioselectivity (entry 11, Table 1). The absolute

• configuration of the product was assigned as (S) by comparing the sign of the optical rotation with that reported in literature [28]. Under the optimized reaction conditions (2 mol % of Pd2(dba)3, 4 mol % of L1d, 300 mol % of CH2(COOMe)2, 300 mol % of BSA and 3 mol % of NaOAc in DCE at 0 °C; entry 9, Table 1

Synthesis of a sucrose dimer with enone tether; a study on its functionalization

• Zbigniew Pakulski,
• Norbert Gajda,
• Magdalena Jawiczuk,
• Jadwiga Frelek,
• Piotr Cmoch and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2014, 10, 1246–1254, doi:10.3762/bjoc.10.124

• surprising. The assignment of the configuration of this diol was further confirmed also by the CD methodology; this is discussed in the next chapter. Determination of the absolute configuration of 11 and 13 It is widely acceptable that the circular dichroism (CD) spectroscopy utilizing the in situ

• dimolybdenum methodology offers the hard proof of the absolute configuration of the vic-diols [27][28][29]. In this methodology, dimolybdenum tetraacetate acts as auxiliary chromophore allowing the application of electronic circular dichroism (ECD) to (otherwise in ECD non-observable) vic-diols. Mo2(OAc)4 when

• positive/negative signs of Cotton effects (CE) occurring in the 300–400 nm spectral range in the ECD spectra with the positive/negative sign of the O–C–C–O torsion angle of the diol unit of resultant complexes with the Mo2-core. The basic assumption leading to the assignment of the absolute configuration

Heronapyrrole D: A case of co-inspiration of natural product biosynthesis, total synthesis and biodiscovery

• Jens Schmidt,
• Zeinab Khalil,
• Robert J. Capon and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2014, 10, 1228–1232, doi:10.3762/bjoc.10.121

• the relative as well as the absolute configuration [3][4] (recently, verified by Brimble et al. [5]). Building on these achievements, and in a departure from traditional natural products discovery, this report describes an innovative collaborative strategy that employed biosynthetic considerations

• [α]D22 +3.9 (c 0.1, MeOH)], established that heronapyrrole D was indeed a natural product, and that it possessed the structure and absolute configuration as proposed (see Supporting Information File 1, Figure S2). As with the known heronapyrroles A–C [1], heronapyrrole D exhibited growth inhibitory

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• addition by X-ray crystallography as (2R,3S) for the amino alcohol and thus, due to altered priorities, (2S,3S) for the corresponding amino acid, respectively. The absolute configuration was deduced assuming the integrity of the stereocenter at the 2-position, which had been derived from D-serine (2). As

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• 20, B-7000 Mons, Belgium 10.3762/bjoc.10.105 Abstract Methods were developed and optimized for the preparation of the 2,3-cis- and the 10,11-cis-isomers of silybin by the Lewis acid catalyzed (BF3∙OEt2) isomerization of silybins A (1a) and B (1b) (trans-isomers). The absolute configuration of all

• availability of (potential) minor impurities is a fundamental requisite, e.g., for master file assembly. The aim of this work was to prepare stereochemically pure 2,3-cis- and 10,11-cis-isomers of silybin A (1a) and B (1b) by a Lewis acid catalyzed isomerization to determine their absolute configuration and to

• -cis-10,11-trans-isomer 12 and a minor 23-O-acetyl-2,3-trans-10,11-cis-isomer 13 (Scheme 3). Surprisingly, the absolute configuration at C-2, C-3 of compound 13 was the opposite of 1a (2S,3S vs 2R,3R), which was confirmed by a comparison of their electronic circular dichroism (ECD) data. Formation of

Molecular architecture with carbohydrate functionalized β-peptides adopting 3₁₄-helical conformation

• Nitin J. Pawar,
• Navdeep S. Sidhu,
• George M. Sheldrick,
• Dilip D. Dhavale and
• Ulf Diederichsen

Beilstein J. Org. Chem. 2014, 10, 948–955, doi:10.3762/bjoc.10.93

• based on X-ray data, the 6R absolute configuration and the formation of the D-glycero-isomer were confirmed (Figure 3). Therefore, the minor isomer 10a was assigned the 6S absolute configuration. The formation of major isomer 10b can be explained based on the Felkin–Anh model. Thus, the ammonia

Primary-tertiary diamine-catalyzed Michael addition of ketones to isatylidenemalononitrile derivatives

• Akshay Kumar and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2014, 10, 929–935, doi:10.3762/bjoc.10.91

• time of 6 days (Table 5, entry 13). The R absolute configuration of Michael adducts was assigned by comparing the HPLC chromatograms of Michael adducts with that reported in the literature [23][24]. Next, we studied the multicomponent version of this reaction. Acetone, isatin and malononitrile react in

Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination

• Łukasz Górecki,
• Artur Mucha and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 883–889, doi:10.3762/bjoc.10.85

• were not fully consumed. Partially stereoselective addition was observed for the shorter homolog 4. The diastereomeric excess of the newly appearing stereogenic center at C10 of α-hydroxyphosphonate 9 slightly depended on the reaction conditions and the C3 absolute configuration of the substrate, and

• fragment (being the result of induction of the same C10 configuration, see the inserted spectrum in Scheme 3). Thus, general stereo-controlling properties of quinine predominate and do not cooperate (no match–mismatch effect visible) with the absolute configuration of the starting aldehyde epimers. The

Structure elucidation of female-specific volatiles released by the parasitoid wasp Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

• Armin Tröger,
• Teris A. van Beek,
• Martinus E. Huigens,
• Isabel M. M. S. Silva,
• Maarten A. Posthumus and
• Wittko Francke

Beilstein J. Org. Chem. 2014, 10, 767–773, doi:10.3762/bjoc.10.72

• approach includes a formal synthesis of optically active A and B. Until now, we did not find suitable conditions to separate the enantiomers of the tetramethyldiene 22 and the respective allyl alcohol 23 (or corresponding derivatives thereof) in order to assign the absolute configuration of the natural

• corrected the structures of the initially published Trichogramma compounds and showed a way to determine the enantiomeric composition of the natural products. Details including the assignment of the absolute configuration of the compounds will be published separately. As yet, the biological significance of