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

• structures clearly revealed the presence of a weak gold–π interaction between the Au atom and the aromatic rings in these gold complexes. Because of the gold–π interaction, the C–N bond could not rotate freely, giving two diastereomeric rotamers (S)-15a and (S)-15b. Slaughter and co-workers have also found

• two rotamers in gold complexes 1 caused by the handicap of C–N bond rotation on the basis of X-ray diffraction and named them as “out” rotamer and “in” rotamer [49] (Scheme 5). Their energy barrier has been also disclosed by DFT calculations. Synthesis of the P–Au(I) complexes. The synthesis of the Au

• = 1525.9(2) Å3; space group: P2(1); Z = 4; Dcalc = 1.626 g/cm3; F000 = 732; final R indices [I > 2sigma(I)]: R1 = 0.0231; wR2 = 0.0538. Synthesis of compound 9. Synthesis of N-heterocyclic carbene precursor. Synthesis of benzimidazolium salt (S)-14. Synthesis of carbene Au complexes. Rotamers of 1a and 1b

The first example of the Fischer–Hepp type rearrangement in pyrimidines

• Inga Cikotiene,
• Mantas Jonusis and
• Virginija Jakubkiene

Beilstein J. Org. Chem. 2013, 9, 1819–1825, doi:10.3762/bjoc.9.212

• (C-2) ppm; HRMS (ES): [M + Na]+ calcd for C19H19N5NaOS, 388.1203; found, 388.1206. N4-Benzyl-N6-butyl-2-methylthio-5-nitrosopyrimidine-4,6-diamine (6ee): Blue solid; yield 89%; mp 82–84 °C; IR (KBr): νmax 3249 (NH) cm−1; NMR spectra contain signals of two rotamers. 1H NMR (400 MHz, CDCl3, 25 °C) δ

α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions

• Åsmund Kaupang and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2013, 9, 1407–1413, doi:10.3762/bjoc.9.157

• resolved their structures by single-crystal X-ray diffraction. The diazoacetamides 3d and 3f crystallised as their (Z)-rotamers. These data have recently been reported [42][43]. The diazoacetamides were brominated at −5 °C with NBP in the presence of DBU and passed through a dry-ice-cooled plug of silica

High-spin intermediates of the photolysis of 2,4,6-triazido-3-chloro-5-fluoropyridine

• Sergei V. Chapyshev,
• Denis V. Korchagin,
• Patrik Neuhaus and
• Wolfram Sander

Beilstein J. Org. Chem. 2013, 9, 733–742, doi:10.3762/bjoc.9.83

• 11 the azido groups in ortho-positions to the fluorine atom should be the most photoactive. The photodissociation of the azido groups in triazide 11 can be modeled by computational methods [8][34]. Thus, for instance, the geometry optimizations of the most stable rotamers 11a and 11b in their lowest

Synthesis and evaluation of cell-permeable biotinylated PU-H71 derivatives as tumor Hsp90 probes

• Tony Taldone,
• Anna Rodina,
• Erica M. DaGama Gomes,
• Matthew Riolo,
• Hardik J. Patel,
• Raul Alonso-Sabadell,
• Danuta Zatorska,
• Maulik R. Patel,
• Sarah Kishinevsky and
• Gabriela Chiosis

Beilstein J. Org. Chem. 2013, 9, 544–556, doi:10.3762/bjoc.9.60

• -PEO3-Biotin. It should be noted that in each of the products (2b, 2d, 2f, 2h) derived from 1a it was not immediately clear whether these were a mixture of two compounds or rotamers, despite the seeming unambiguity in the synthesis. While HPLC showed a single homogeneous peak, the NMR spectrum was very

• rotamers was present and not a mixture of two compounds. Additionally, intermediate 3 also demonstrates a complex NMR spectrum indicative of the presence of two rotamers. All of this shows that, unlike the proton, the isopropyl group is bulky enough to hinder rotation of the tertiary amides and to enable

• identification of two rotamers by NMR [22]. Biological evaluation of the biotinylated Hsp90 probes As indicated above, there are several requirements for a biotinylated probe to be useful in dissecting Hsp90 tumor biology in live cells. First, the probe should retain selective and tight binding to tumor Hsp90

De novo synthesis of D- and L-fucosamine containing disaccharides

• Daniele Leonori and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 332–341, doi:10.3762/bjoc.9.38

• , 1240, 1071; 1H NMR (400 MHz, CDCl3, rotamers) δ 8.04 (d, 2H, J = 7.3 Hz, 2 × CH), 7.57 (tt, J = 7.4, 1H, 1.2 CH), 7.44 (t, J = 7.7 Hz, 2H, 2 × CH), 7.35–7.22 (m, 17H, 17 × CH), 7.17–7.04 (m, 8H, 8 × CH), 5.88 (br d, J = 6.5 Hz, 0.5H, NH), 5.73 (br d, J = 6.0 Hz, 0.5H, NH), 5.21 (dd, J = 9.1, 8.0 Hz, 1H

• , CHN), 3.67 (q, J = 6.4 Hz, 1H, CHB), 3.50 (br dt, J = 9.6, 2.3 Hz, 1H, CHK), 3.44–3.40 (m, 1H, CHN), 3.23–3.17 (m, 3H, CHE and CH2P), 1.85 and 1.81 (s, 3H, CH3), 1.53–1.50 (m, 3H, 3 × CHO), 1.45 (s, 3H, CH3), 1.29–1.21 (m, 3H, 3 × CHO), 1.08 (d, J = 6.4 Hz, 3H, CH3A); 13C NMR (100 MHz, CDCl3, rotamers

The diketopiperazine-fused tetrahydro-β-carboline scaffold as a model peptidomimetic with an unusual α-turn secondary structure

• Francesco Airaghi,
• Andrea Fiorati,
• Giordano Lesma,
• Manuele Musolino,
• Alessandro Sacchetti and
• Alessandra Silvani

Beilstein J. Org. Chem. 2013, 9, 147–154, doi:10.3762/bjoc.9.17

• = 7.1 Hz); 13C NMR (CDCl3, 75.4 MHz, mixture of two rotamers) δ 175.4 and 174.5, 171.8 and 170.7, 155.7 and 155.6, 143.7, 143.6, 141.2 (2C), 127.7 (2C), 127.1 (2C), 124.9 (2C), 120.0 (2C), 68.6 and 68.2, 62.2 and 61.8, 55.7 and 55.5, 47.6 and 47.1, 47.0, 15.5 and 14.9, 14.1; IR (cm−1): 2954, 1750, 1709

Inclusion of the insecticide fenitrothion in dimethylated-β-cyclodextrin: unusual guest disorder in the solid state and efficient retardation of the hydrolysis rate of the complexed guest in alkaline solution

• Dyanne L. Cruickshank,
• Natalia M. Rougier,
• Raquel V. Vico,
• Susan A. Bourne,
• Elba I. Buján,
• Mino R. Caira and
• Rita H. de Rossi

Beilstein J. Org. Chem. 2013, 9, 106–117, doi:10.3762/bjoc.9.14

• (distinguishable as rotamers with respect to the P–OAr bond) while in the other, three distinct guest components with site-occupancies 0.44, 0.29 and 0.27 appear, the last having a reversed orientation relative to all the other components. Kinetic studies of the alkaline hydrolysis of fenitrothion in the presence

• ]. A crystalline inclusion complex (TRIMEA)2·1 was isolated and shown by X-ray analysis to contain a novel capsule formed by head-to-head contact of the secondary rims of two TRIMEA molecules [5]. The encapsulated fenitrothion molecule showed minor disorder in the form of two rotamers (with respect to

• . Here, a single molecule of fenitrothion occupies the cavity, being present as two rotamers whose phosphorothioate groups are related by a rotation of 126° around the O11–P12 bond. The phosphorothioate group of each disordered component of the guest 1 is located near the primary side of the host

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• the rotation of the alkyne group to the proper position for the cycloaddition to occur (Scheme 7). The NMR spectra also supported this hypothesis: While all tertiary amides showed the presence of two rotamers in a 1:1 ratio in CDCl3, the secondary amides 13b and 13c showed only a single rotamer in the

Synthesis and antiviral activities of spacer-linked 1-thioglucuronide analogues of glycyrrhizin

• Christian Stanetty,
• Andrea Wolkerstorfer,
• Hassan Amer,
• Andreas Hofinger,
• Ulrich Jordis,
• Dirk Claßen-Houben and
• Paul Kosma

Beilstein J. Org. Chem. 2012, 8, 705–711, doi:10.3762/bjoc.8.79

• , 11, 14, 15 and 17–19 revealed complex spectra. Whereas the secondary amides of 3β-amino-glycyrrhetinic acid derivatives displayed coherent NMR signals [22][23], the tertiary amides frequently exist as mixtures of cis/trans rotamers leading to the duplication of signals [24][25]. The steric congestion

• . Reversible coalescence of these signal groups was observed upon heating a solution of the N-acetyl derivative 11 up to 100 °C in DMSO-d6 and subsequent cooling to room temperature (Figure 2), supporting the assignment of two signal data sets for two rotamers. The orientation of the amide carbonyl group in

• the rotamers also had a pronounced effect on the NMR chemical shifts of carbon and proton signals in ring A, which led to a shift of H-3 to lower field (δ 4.47) and to a shielding of C-3 (δ 59.9) for the minor isomer, whereas the inverse effects were seen for the major rotamer (δ for H-3 at 3.36 and δ

NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

• Damjan Makuc,
• Jennifer R. Hiscock,
• Mark E. Light,
• Philip A. Gale and
• Janez Plavec

Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140

• conformer is unlikely to be abundant in the absence of anions, due to repulsion between the hydrogen bond donor groups. The other two rotamers, namely anti–anti and syn–anti, can be stabilized by intramolecular NH–CO hydrogen bonds, which represent competition to anion–receptor interactions and therefore

• evaluate the role of DMSO on the energetic preferences of rotamers, relative energies were calculated with the use of Tomasi's polarized continuum model [42][43]. Preferences amongst the three rotamers were retained (Table 4). Only small differences below 1.2 kcal·mol−1 were found between the three

• distinct conformers in the case of the 1·Cl− complex. In particular, the negligible energy differences between syn–syn and syn–anti rotamers are in agreement with the NOE data that suggested predominance of the syn–anti conformer upon addition of chloride. The energetic preference of the syn–syn over the

Fused bicyclic piperidines and dihydropyridines by dearomatising cyclisation of the enolates of nicotinyl-substituted esters and ketones

• Heloise Brice,
• Jonathan Clayden and
• Stuart D. Hamilton

Beilstein J. Org. Chem. 2010, 6, No. 22, doi:10.3762/bjoc.6.22

• many of the signals in the crude 1H NMR spectrum of 14 suggested the existence of either a mixture of diastereoisomers or rotamers caused by restricted rotation of the carbamate group. No dihydropyridine was isolable from this mixture by flash chromatography, probably due to rapid re-aromatisation

Synthesis of (S)-1-(2-chloroacetyl)pyrrolidine- 2-carbonitrile: A key intermediate for dipeptidyl peptidase IV inhibitors

• Santosh K. Singh,
• Narendra Manne and
• Manojit Pal

Beilstein J. Org. Chem. 2008, 4, No. 20, doi:10.3762/bjoc.4.20

• -proline 7). N-Acylproline derivatives are known to exist as a mixture of cis- and trans-amide rotamers in solution. The same has been observed in case of N-acyl-2-cyanopyrrolidines [6]. Thus, as indicated by 1H NMR spectra the protons at C-2 position of the pyrrolidine ring (and of the CH2Cl group) tended

• to appear separately in the corresponding spectra (Figure 3, see Supporting Information File 1). The presence of rotamers was also evident in the 13C NMR spectra (Figure 4, see Supporting Information File 1). Based on 1H NMR data it was possible to calculate the ratio of rotamers present in the

• resulting crystalline solid was filtered and washed with cold hexane to give the target compound 6 (3.0 g, yield 83%); HPLC Purity: 99.25%; mp 52–53 °C (lit [6] 53–57 °C); IR (KBr-, cm-1): 3304, 2992, 2953, 2888, 2242, 1662, 1424; 1H NMR (300 MHz, CDCl3) δ (4:1 mixture of trans/cis amide rotamers) 2.1–2.4

The enantiospecific synthesis of (+)-monomorine I using a 5-endo- trig cyclisation strategy

• Malcolm B. Berry,
• Donald Craig,
• Philip S. Jones and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2007, 3, No. 39, doi:10.1186/1860-5397-3-39

• diastereoisomers. Although this stereochemical relationship could not be discerned from the 1H NMR spectra of 14 due to peak broadening caused by amide rotamers, a combination of further elaboration and X-ray crystallographic analysis confirmed the assignment. Deprotection of simple benzoyl-protected pyrrolidines