Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• Sagarika Samantray Sreenivasulu Bandi Dillip K. Chand Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India 10.3762/bjoc.15.109 Abstract The complexation study of cis-protected and bare palladium(II) components with a new tridentate ligand, i.e., pyridine-3,5

• -diylbis(methylene) dinicotinate (L1) is the focus of this work. Complexation of cis-Pd(tmeda)(NO3)2 with L1 at a 1:1 or 3:2 ratio produced [Pd(tmeda)(L1)](NO3)2 (1a). The reaction mixture obtained at 3:2 ratio upon prolonged heating, produced a small amount of [Pd3(tmeda)3(L1)2](NO3)6 (2a). Complexation

• ]. Complexation of cis-protected palladium(II), i.e., (PdL’) or bare palladium(II) with non-chelating bidentate ligands is known to afford a series of (PdL’)mLm or PdmL2m-type self-assembled coordination complexes [5]. Pd2L4-type cages are the simplest representatives among the PdmL2m-type complexes, yet most

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• Abstract Four benzothiazolium crown ether-containing styryl dyes were prepared through an optimized synthetic procedure. Two of the dyes (4b and 4d) having substituents in the 5-position of the benzothiazole ring are newly synthesized compounds. They demonstrated a higher degree of trans–cis

• constants of metal complexes were determined and are in good agreement with the literature data for reference dyes. The temporal evolution of trans-to-cis isomerization was observed in a real-time regime. The dyes demonstrated a low intrinsic fluorescence of their Ba2+ complexes and high yield of E/Z

• photoisomerization with lifetimes of the higher energy form longer than 500 seconds. Density functional theory (DFT) calculations at the B3LYP/6-31+G(d,p) level were performed in order to predict the enthalpies (H) of the cis and trans isomers and the storage energies (ΔH) for the systems studied. Keywords: aza-15

New terpenoids from the fermentation broth of the edible mushroom Cyclocybe aegerita

• Frank Surup,
• Florian Hennicke,
• Nadine Sella,
• Maria Stroot,
• Steffen Bernecker,
• Sebastian Pfütze,
• Marc Stadler and
• Martin Rühl

Beilstein J. Org. Chem. 2019, 15, 1000–1007, doi:10.3762/bjoc.15.98

• -H2 to C-6/C-7 and 8-H to C-6/C-7/C-13. The strong ROESY correlation between 2-H and 9-H indicated a cis configuration between these protons, and the large coupling constant between 8-H and 9-H, observed in the signal of 8-H, a trans configuration of 8-H/9-H. Finally, the ROESY correlation between 12

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• with λ = 365 nm reveals a photoisomerization of the co-ligand from the trans to the cis form. Keywords: azobenzene carboxylates; cadmium; complexes; macrocyclic ligands; nickel; zinc; Introduction The macrocyclic N6S2 donor ligand H2L is an effective dinucleating ligand that supports a large number

• drastically alter its structural properties and reactivities. Prominent examples are the cis-bromination of α,β-unsaturated carboxylato ligands [2], regioselective Diels–Alder reactions of encapsulated dienoate ligands [3], and the stabilization of unusual co-ligand conformations, respectively [4]. The

• -allowed 3A2g(F) → 3T2g(F) (ν3) transition is expected around 440 nm, but is obscured by the stronger RS → Ni2+ charge transfer and π→π* transitions in this region. We carried out orienting irradiation experiments with regard to a possible trans to cis photoisomerization of the bound azobenzene-carboxylate

Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines

• Camila B. Francisco,
• Cleverton S. Fernandes,
• Ulisses Z. de Melo,
• Roberto Rittner,
• Gisele F. Gauze and
• Ernani A. Basso

Beilstein J. Org. Chem. 2019, 15, 818–829, doi:10.3762/bjoc.15.79

• Abstract The presence of strong stereoelectronic interactions involving the substituents in cis-2-substituted cyclohexanes may lead to results different from those expected. In this work, we studied the conformational behavior of cis-2-fluoro- (F), cis-2-chloro- (Cl), cis-2-bromo- (Br) and cis-2

• preference for the ea conformer in cis-2-halocyclohexylamines, being strong enough to restrain the shift in the equilibrium due to other factors such as steric repulsion or solvent effects. Keywords: conformational equilibrium; cyclohexane derivatives; dynamic NMR; hyperconjugation; principal component

• analysis; Introduction cis-2-Substituted cyclohexanes are interesting from the conformational point of view, since one of the substituents should be axial. Generally, bulky substituents prefer the equatorial position to avoid steric repulsions [1]. Nevertheless, two distinct groups may provoke a

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• photo-induced trans–cis isomerization representing the time of birth of the azobenzene photoswitch. Benefiting of their accessible synthesis, large change in polarity and geometry upon switching, excellent photochromic properties and tuneability, azobenzenes are amongst the most widely used photochromic

• trans-isomer as biologically active configuration whereas its bent cis-isomer should be inactive. Synthesis of the quinoxaline-based azobenzenes The synthesis of the unsubstituted quinoxaline-based azobenzene derivatives 5a and 5b is based on a Baeyer [62]–Mills [63] reaction (Scheme 2). Therefore

• performed in DMSO and depending on their solubility in phosphate buffer + 0.1% DMSO (16a–d) by UV–vis absorption spectroscopy. The compounds were dissolved at 50 µM in the respective solvent and irradiated with the indicated wavelengths to generate a substantial amount of their cis-isomer. This process can

Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials

• Widukind Moormann,
• Daniel Langbehn and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 727–732, doi:10.3762/bjoc.15.68

• , amine and vinyl groups, which are suitable for polymer synthesis. Upon irradiation at 385 and 530 nm the diazocines perform a reversible, pincer-type movement switching the 3,3’-distance between 6.1 Å (cis, stable isomer) and 8.2 Å (trans, metastable isomer). Key reactions in the synthesis are an

• to 3,3’- and 4,4’-diaminodiazocine, which have been implemented in macromolecules for conformation switching, our compounds exhibit improved photophysical properties (photostationary states, separation of absorption bands in the cis and trans configuration). Hence they are promising candidates as

• functionalized compounds are rare [19][20][21][22][23]. In contrary to azobenzenes, diazocines 1 are stable in their cis configuration. The bent cis isomer is less prone to π–π stacking which is known to reduce the switching efficiency (Figure 1a) [19][24]. The reverse stability of the cis and trans isomers in

Dirhodium(II)-catalyzed [3 + 2] cycloaddition of N-arylaminocyclopropane with alkyne derivatives

• Wentong Liu,
• Yi Kuang,
• Zhifan Wang,
• Jin Zhu and
• Yuanhua Wang

Beilstein J. Org. Chem. 2019, 15, 542–550, doi:10.3762/bjoc.15.48

• no cis product formed. After further removal of the para-methoxyphenyl (PMP) group using ammonium cerium nitrate (CAN), the cyclic β-amino acid ester 5b was obtained with a yield of 80%. Cyclic β-amino acids and derivatives have good bioactivity and are widely used as key synthetic intermediates in

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• -metathesis of allyl alcohol (59) and the cis–trans isomerization of cis-butenedienol (Z-58). Metathesis catalysts bearing quaternary ammonium groups provide an attractive alternative to classical ruthenium catalysts. Although they do not represent a great improvement in terms of catalytic activity, they

• diallylmalonate 31 in DCM (Scheme 11). Upon reaction completion, the catalyst is extracted from the organic reaction mixture with D2O and (re)-used for the isomerization of cis-butenediol Z-58 in water. Recently the removal of a water-soluble catalyst from reaction mixtures was also achieved with catalyst 12

Convergent synthesis of the pentasaccharide repeating unit of the biofilms produced by Klebsiella pneumoniae

• Arin Gucchait,
• Angana Ghosh and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2019, 15, 431–436, doi:10.3762/bjoc.15.37

• the 1,2-cis glycosylated product of the D-mannose moiety (β-mannoside), which was considered as a challenging task in spite of several reaction strategies developed in the recent past [16][27][28][29][30][31][32][33]. Among several elegant reaction conditions, it was decided to apply a two-step

• activation of the benzylidene-thiomannoside donor in the presence of a combination of 1-benzenesulfinylpiperidine (BSP) and 2,4,6-tri-tert-butylpyrimidine (TTBP) and then triflic anhydride (Tf2O) developed by Crich et al. [28][29]. Stereoselective 1,2-cis glycosylation of D-mannose-derived ethyl 4,6-O

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• these interfere with planned chemical modifications of NR+X− on the 5′-C-hydroxy moiety. The most common approaches convert the cis-2′,3′-hydroxy groups of NR+X− to an acetonide (i.e., 2′,3′-O-isopropylidene nicotinamide riboside 29; isopro-NR) in a reaction with 2,2-dimethoxypropane in the presence of

Annulation of 1H-pyrrole-2,3-diones by thioacetamide: an approach to 5-azaisatins

• Aleksandr I. Kobelev,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2019, 15, 364–370, doi:10.3762/bjoc.15.32

• formed very slowly and readily underwent multiple side-reactions. The involvement of propanethioamide and 2-phenylethanethioamide did not give any desirable results, too. These interactions provided mixtures of three isomeric adducts possibly corresponding to two stereoisomeric adducts (cis and trans

Reusable and highly enantioselective water-soluble Ru(II)-Amm-Pheox catalyst for intramolecular cyclopropanation of diazo compounds

• Hamada S. A. Mandour,
• Yoko Nakagawa,
• Masaya Tone,
• Hayato Inoue,
• Nansalmaa Otog,
• Ikuhide Fujisawa,
• Soda Chanthamath and
• Seiji Iwasa

Beilstein J. Org. Chem. 2019, 15, 357–363, doi:10.3762/bjoc.15.31

• determined to be (1S,5R,6R) by single-crystal X-ray diffraction analysis (Supporting Information File 1) [51]. Since the stereoselectivity of products depends on the cis/trans geometry of the reactants, other stereoisomers such as the (1S,5R,6S) product was not formed in this catalytic cyclopropanation

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• phosphinite 6a which afforded a 73:27 mixture of the diastereomeric phosphine oxides 7a/7’a (86%). The major diastereomer 7a corresponds to a sigmatropic rearrangement occurring on the most hindered face (cis to the aromatic group) of the cyclopropene which was somewhat surprising. Substitution at the para

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• order to remove ethene, because ethene would strongly slow down the desired cross metathesis and inactivate Schrock-type metathesis catalysts. CM of OVS with styrenes proceeded stereoselectively. A mixture of cis- and trans-isomers was obtained in the transformations of other olefins tested

Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• allows sigmatropic rearrangements leading to odd-numbered carbocyclic derivatives [8]. In this sense, seven-membered carbocycles, namely 1,4-cycloheptadienes, can be forthrightly prepared from cis- or trans-1,2-divinylcyclopropanes through a Cope rearrangement [8][9]. The potential of this type of

• equimolar mixture of cis/trans diastereoisomers (cis refers to both vinyl substituents). Even though the lack of selectivity was already noticed by Uemura and co-workers in related reactions [17], we attempted the reaction with other zinc salts or rhodium(II) carboxylates as catalysts. Unfortunately, these

• experiments were futile and led to similar low selectivities. Besides, gaseous 1,3-butadiene could be also employed, as demonstrated by the preparation of compounds 3i,j, which were obtained in moderate yields and low cis selectivities. The reaction with isoprene showed a remarkable selectivity for the most

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

• ) [53]. Starting from O-benzyl-D-serine (2S,3R)-2 was obtained in a similar way. Configurationally stable D-serinal derivative (R)-23 (prepared from D-serine [54]) which primarily exists as hemiacetal was subjected to cis-olefination with Stille's reagent at −30 °C to produce (S)-24 in good yield

• O-benzyl-L-serine. Reagents and conditions: a) (CF3CH2O)2P(O)CH2COOMe, KHMDS, 18-crown-6; b) I2, MeCN; c) Bu3SnH, AIBN, benzene, reflux; d) H2, 10% Pd/C, ethanol; e) CrO3, acetone, then CH2N2, ether; f) 3 M HCl, 80 °C. Synthesis of (2S,3R)-2 employing a one-pot cis-olefination–conjugate addition

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• -telechelic poly(1,4-butadiene) bearing alkoxyamine termini was obtained by ROMP of trans,trans,cis-1,5,9-cyclododecatriene in the presence of a symmetric acyclic olefin CTA (Scheme 2). This telechelic polybutadiene was used as the macroinitiator for the NMP of styrene and diene monomers to yield unimodal SBS

• for the formation of NB–COE copolymer [95]. Some results regarding the cis/trans-isomerization of double bonds in the MCM process were obtained [85][87][89]. In the systems PNB–PCOE (68% cis)–Gr1 and PBD–cis-olefin-containing polyurethane (cis-PU)–Gr2, cis-double bonds partly transform to a more

• thermodynamically stable trans-configuration, which is well-known for olefin metathesis [85][89]. The cis/trans-isomerization is observed for homodyads in MCM and even in the course of the homopolymer–catalyst interaction as a result of self-metathesis reactions that do not directly influence the copolymer

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• of methyl 9-dodecene and in hexane for the RO-RCM of cis-cyclooctene. The above-mentioned studies clearly illustrate the versatility and use of ruthenium alkylidene complexes with pyridinyl-alcoholato ligands. In principle these studies had one approach in common concerning the pyridinyl-alcoholato

• in 10 °C intervals between 70 and 110 °C. Results and Discussion A mixture of products, summarised in Table 1, is obtained during the metathesis of 1-octene, i.e., primary metathesis products (PMPs), isomerisation products (IPs) and secondary metathesis products (SMPs). The PMPs, 7-tetradecene (cis

• and trans) and ethene, forms as a result of the self-metathesis (SM) of 1-octene. Simultaneously 1-octene is isomerised to 2-, 3- and 4-octene (IPs). The subsequent SM and CM reactions of the internal alkenes yield alkenes (cis and trans) in the C3–C13 range (SMPs). All the reactions were followed by

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• positions 4 and 6 of GalNAc units favor the formation of 1,2-cis glycosidic bonds, even in the presence of 2-participating groups [43][44]. Treatment with (HF)n·Py complex in THF followed by standard acetylation provided compound 7. This derivative displayed a suitable protecting group distribution for the

• revealed that the pivaloyl functions in the glycosyl acceptor favored the formation of the 1,2-cis glycosidic bond even in the presence of the N-TFA participating group in the glycosyl donor. In contrast, 2,3-di-O-benzoyl/benzyl GlcA derivatives exclusively gave the β-anomer. Overall, our results highlight

Systematic synthetic study of four diastereomerically distinct limonene-1,2-diols and their corresponding cyclic carbonates

• Hiroshi Morikawa,
• Jun-ichi Yamaguchi,
• Shun-ichi Sugimura,
• Masato Minamoto,
• Yuuta Gorou,
• Hisatoyo Morinaga and
• Suguru Motokucho

Beilstein J. Org. Chem. 2019, 15, 130–136, doi:10.3762/bjoc.15.13

• )-limonene-derived diol and its corresponding five-membered cyclic carbonate were prepared. The diol (cyclic carbonate) comprises four diastereomers based on the stereochemical configuration of the diol (and cyclic carbonate) moiety. By choosing the appropriate starting compounds (trans- and cis-limonene

• , we report the synthesis of 1a from the trans-isomer of (R)-limonene oxide (LO) and 1d from cis-LO using CO2 and tetrabutylammonium chloride (TBAC) as a catalyst. Both reactions proceeded without any side reactions and produced no unwanted isomers, such as 1c. Though the CO2 pressure employed in our

• , respectively (Scheme 3). Conversely, the reaction of cis-LO with water afforded only 2b, which was obtained in 70% yield after purification. These results are in good agreement with those of previous reports [18][20][32]. Similarly to the aforementioned carbonation of 2a (Scheme 2), 2b and 2c were also reacted

Selective ring-opening metathesis polymerization (ROMP) of cyclobutenes. Unsymmetrical ladderphane containing polycyclobutene and polynorbornene strands

• Yuan-Zhen Ke,
• Shou-Ling Huang,
• Guoqiao Lai and
• Tien-Yau Luh

Beilstein J. Org. Chem. 2019, 15, 44–51, doi:10.3762/bjoc.15.4

• corresponding soluble acetate. Both polymers are well characterized by spectroscopic means. No norbornene moiety is found to be incorporated into polycyclobutene strand at all. The double bonds in the polycyclobutene strand are mainly in cis configuration (ca 70%), whereas the E/Z ratio for polynorbornene

• agreement with those of 14 and 8. The 13C NMR spectrum of 7 shows two peaks at δ 40.6 and 45.4 ppm, attributed to the allylic carbons attached to a cis and a trans double bond [13], respectively, and the relative ratio of these two peaks is roughly 7:3. This result suggests that about 70% of the double

• bonds in 7 might adopt cis configuration. Moreover, no norbornene moiety was detected by NMR on the polymeric backbones in 7 (Scheme 7). Since 18 was insoluble in most organic solvents, acetylation of 18 with excess acetic anhydride and pyridine at 70 °C for 10 h gave the corresponding acetate 19, which

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• % conversion, respectively, in four days. In the CM of allylbenzene (13) with cis-1,4-diacetoxy-2-butene (14, Scheme 4), the fluorinated complexes 3a–5a and 3b–5b exhibited activities comparable to GII-SIMes and HGII-SIMes, showing higher Z-selectivity at conversions above 60%. For example, catalyst GII-SIMes

• -containing unsymmetrical catalysts 31–34 characterized by alkyl N-substituents with variable steric bulk (Figure 8) [22]. The catalytic performances of these complexes and of complex 24a were evaluated for the RCM of diethyl diallylmalonate (7) and the ROMP of cis-1,5-cyclooctadiene (16). In the RCM reaction

• 35 (Figure 9) was isolated and tested in the RCM of 7 and the ROMP of cis-1,5-cyclooctadiene (16), where it displayed a fair olefin metathesis activity compared to the benchmark catalyst GII-SIMes [23]. Studies on this class of unsymmetrical NHC ligands were also extended to the Hoveyda-type

Repurposing the anticancer drug cisplatin with the aim of developing novel Pseudomonas aeruginosa infection control agents

• Mingjun Yuan,
• Song Lin Chua,
• Yang Liu,
• Daniela I. Drautz-Moses,
• Joey Kuok Hoong Yam,
• Thet Tun Aung,
• Roger W. Beuerman,
• May Margarette Santillan Salido,
• Stephan C. Schuster,
• Choon-Hong Tan,
• Michael Givskov,
• Liang Yang and
• Thomas E. Nielsen

Beilstein J. Org. Chem. 2018, 14, 3059–3069, doi:10.3762/bjoc.14.284

• , transplatin, cDPCP, oxaliplatin, K2PtCl4 and cis-PtCl2(CH3CN)2 were purchased from Sigma-Aldrich were used as received. Platinum complexes cis-PtCl2(Py)2 [13][14] and cis-PtCl2(PPh3)2 [15] were prepared according to the reported procedure. For minimal inhibitory concentration (MIC) assays, cisplatin, cDPCP

• , oxaliplatin, K2PtCl4 and cis-PtCl2(CH3CN)2 were dissolved in saline solution (0.85% w/v) at 2.5 mM concentration, while transplatin, cis-PtCl2(Py)2 and cis-PtCl2(PPh3)2 were dissolved in DMF (v/v) at 2.5 mM concentration. Determination of minimal inhibitory concentration (MIC) The MIC assays were performed

Nucleofugal behavior of a β-shielded α-cyanovinyl carbanion

• Rudolf Knorr and
• Barbara Schmidt

Beilstein J. Org. Chem. 2018, 14, 3018–3024, doi:10.3762/bjoc.14.281

• laboratory time scale in the solvents THF, Et2O, t-BuOMe, or toluene. A similarly weak solvent dependence had been observed [4] for the heterolytic cis/trans stereoinversion of 2Li. (v) For more profound mechanistic investigations, one should be aware of the established [4] clustered ground state of 2Li and

• %) with mp 146–149 °C. 1H NMR (CDCl3, 400 MHz) δ 0.39 (m, 1H of cyclopropyl-CH2 cis to HCO), 0.65 (m, 2 × trans-H), 0.76 (m, 1 cis-H), 1.41 (m, 1H, tert-CH of cyclopropyl), 1.49 and 1.57 (2 s, 2 × 3H, 2 × 3-CH3), 1.69 and 1.71 (2 s, 2 × 3H, 2 × 1-CH3), 1.98 (d, 3J = 4.6 Hz, 1H, exchangeable with D2O, OH