Synthesis of 8‐substituted tetrahydro‐γ‐carbolines

The Fischer reaction is applied to the synthesis of 8‐substituted tetrahydro‐γ‐carbolines with electron‐donating or electron‐withdrawing groups, using catalytic or thermal methods. The reaction conditions must be varied according to the nature of the N 1 substituent of the piperidone. The best results are observed when a releasing group is present on the arylhydrazine and a benzyl substituent on the nitrogen of piperidone. Formation of carbolines with a withdrawing substituent is observed in soft acidic conditions; in others, reaction ended at the hydrazone level or did not evolve.     

Anticancer Potential of Diiron Vinyliminium Complexes

Invited for the cover of this issue is the group of Fabio Marchetti at the Università di Pisa and Paul J. Dyson at Ecole Polytechnique Fédérale de Lausanne (EPFL). Read the full text of the article at 10.1002/chem.201902885 .     

A Study on the Diastereoselective Synthesis of α‐Fluorinated β3‐Amino Acids by α‐Fluorination

The treatment of a β³‐amino acid methyl ester with 2.2 equiv. of lithium diisopropylamide (LDA), followed by reaction with 5 equiv. of N‐fluorobenzenesulfonimide (NFSI) at ?78° for 2.5 h and then 2 h at 0°, gives syn‐fluorination with high diastereoisomeric excess (de). The de and yield in these reactions are somewhat influenced by both the size of the amino acid side chain and the nature of the amine protecting group. In particular, fluorination of N‐Boc‐protected β³‐homophenylalanine, β³‐homoleucine, β³‐homovaline, and β³‐homoalanine methyl esters, 5 and 9 – 11 , respectively, all proceeded with high de (>86% of the syn‐isomer). However, fluorination of N‐Boc‐protected β³‐homophenylglycine methyl ester ( 16 ) occurred with a significantly reduced de. The use of a Cbz or Bz amine‐protecting group (see 3 and 15 ) did not improve the de of fluorination. However, an N‐Ac protecting group (see 17 ) gave a reduced de of 26%. Thus, a large N‐protecting group should be employed in order to maximize selectivity for the syn‐isomer in these fluorination reactions.     

α‐Chiral Acetylenes Having an All‐Carbon Quaternary Center: Phase Transfer Catalyzed Enantioselective α Alkylation of α‐Alkyl‐α‐alkynyl Esters

Going through the phases : The title reaction was found to proceed by an initial base‐mediated isomerization to allenyl esters and subsequent phase transfer catalyzed alkylation at the α position of the ester (see scheme).

     

Comparison of neutron activation analysis from five ceramic standards of the C.R.A.M. Caen and the Perlman/Asaro-standard

The elemental concentration of the ceramic standard material F, G, H, J and K of the Centre de Recherches Archéologiques Médiévales, Université de Caen have been determined based upon the Perlman/Asaro Standard. The analysis has been done by instrumental neutron activation analysis. Results are given for Fe, Na, K, Ba, Co, Cr, Cs, Eu, Ga, La, Lu, Mn, Rb, Sc, Ta, Yb.     

13‐cis‐β,β‐Carotene and 15‐cis‐β,β‐carotene

13‐cis‐β,β‐Carotene, C₄₀H₅₆, crystallizes with a complete molecule in the asymmetric unit, whereas 15‐cis‐β,β‐carotene, also C₄₀H₅₆, has twofold symmetry about an axis through the central bond of the polyene chain. The polyene methyl groups are arranged on one side of the polyene chains for each molecule and the 6‐s‐cisβ end groups, with the cyclohexene rings in half‐chair conformations, are twisted out of the planes of the polyene chains by angles ranging from 41.37 (17) to 52.2 (4)°. The molecules in each structure pack so that the arms of one occupy the cleft of the next, and there is significant π–π stacking of the almost‐parallel polyene chains of the 15‐cis isomer, which approach at distances of 3.319 (1)–3.591 (1) Å.     

From atoms to biomolecules: a fruitful perspective

We present a summary of the research activities of the “Quantum Chemistry and Atomic Physics” theoretical group of the “Chimie Quantique et Photophysique” Laboratory at Université Libre de Bruxelles. We emphasize the links between the three orientations of the group: theoretical atomic spectroscopy, structure, and molecular dynamics and list the perspectives of our collaboration.     

1‐Ethyl 2,2‐dimethyl 3‐(1,3‐benzodioxol‐5‐yl)propane‐1,2,2‐tricarboxylate

The molecular structure of the title triester compound, C₁₇H₂₀O₈, consists of a benzodioxole fused‐ring system, an ethoxycarbonylmethyl group and two methoxycarbonyl groups arranged around a tetrahedral carbon center. Unlike similar triesters, which are oils, the title compound crystallizes at room temperature as interdigitated bilayers of triester molecules, with short O...H contacts from the methylene H atoms of benzodioxole to the carbonyl O atom of the ethoxycarbonylmethyl group and to a ring O atom of the benzodioxole group of a neighboring molecule within the bilayer. The persistence of these short C—H...O interactions from the activated H atoms of the benzodioxole ring at both 100 and 300 K indicate that they help provide the stabilization necessary for crystallization from the oil.     

Studies on the Mass Spectra of N‐Aryl α,β‐Unsaturated γ‐Lactams

The mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M⁺‐29], [M⁺‐55], and [M⁺‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed.     

Methyl 3‐O‐β‐l‐fucopyranosyl α‐d‐glucopyranoside trihydrate

The water content of the title compound, C₁₃H₂₄O₁₀·3H₂O, creates an extensive hydrogen‐bonding pattern, with all the hydroxyl groups of the disaccharide acting as hydrogen‐bond donors and acceptors. The water molecules are arranged in columns along the crystallographic b axis and form, together with one of the hydroxyl groups, infinite hydrogen‐bonded chains. The conformation of the disaccharide is described by glycosidic torsion angles of −38 and 18°.     

2‐Hydroxy‐4,6‐dimethoxy‐3‐(3‐methylbutanoyl)benzaldehyde

The structure of the title compound, C₁₄H₁₈O₅, has two independent molecules related by a local noncrystallographic a‐glide plane perpendicular to the b axis. The pseudo‐glide plane shows a discontinuity at z = 0. Both molecules have an intramolecular hydrogen bond between the hydroxy and aldehyde groups. There are stacks of molecules along the a‐axis direction. Neighboring molecules in the stack have an interplanar angle of 1.6 (1)°, interplanar distances ranging between 3.399 (3) and 3.417 (3) Å, and a ring offset of 1.38 (1) Å.     

Studies with 3‐functionally substituted 2‐arylhydrazononitriles: A new route to 3‐substituted‐2‐arylhydrazononitriles, 4‐amino‐pyrazole‐5‐carbonitriles,azadienes and cinnolines

3‐Amino‐3‐phenyl‐2‐phenylazoacrylonitrile 6 is obtained in good yield via reaction of 5 with phenyl magnesium bromide. The compound 6 is readily converted into 4a . The so formed alkanenitrile reacted with phenylmagnesium bromide to yield 8 . Compound 8 could be also obtained from reaction of 9 with phenylmagnesium bromide. The arylhydrazononitriles 8 and 4a reacted with chloroacetonitrile to yield the 4‐aminopyrazoles 12a,b . Compound 12a reacted with acetic anhydride to yield the 15a and with benzoyl chloride to yield the pyrazole 16 which was converted into 15b . Refluxing 10 in acetic acid gave a mixture of the azadiene 21 and the cinnoline 22 is obtained. The azadiene 21 is converted into 22 either thermally or photochemically.     

Poly[[triaquazinc(II)]‐μ3‐4‐nitrophthalato‐κ3O1:O2:O2′]

In the title complex, [Zn(C₈H₃NO₆)(H₂O)₃]_n, the two carboxylate groups of the 4‐nitrophthalate dianion ligands have monodentate and 1,3‐bridging modes, and Zn atoms are interconnected by three O atoms from the two carboxylate groups into a zigzag one‐dimensional chain along the b‐axis direction. The Zn atom shows distorted octahedral coordination as it is bonded to three O atoms from carboxylate groups of three 4‐nitrophthalate ligands and to three O atoms of three non‐equivalent coordinated water molecules. The one‐dimensional chains are aggregated into two‐dimensional layers through inter‐chain hydrogen bonding. The whole three‐dimensional structure is further maintained and stabilized by inter‐layer hydrogen bonds.     

Hydrogen‐bonded supramolecular polymers from derivatives of α‐amino‐ε‐caprolactam: A bio‐based material

Hydrogen‐bonded supramolecular polymers were prepared from the derivatives of α‐amino‐ε‐caprolactam (ACL), obtained from a renewable resource. Several self‐complimentary bis‐ or tetra‐caprolactam monomers were synthesized by varying the number of carbons of the spacer between the hydrogen‐bonding end groups. Physical properties of these hydrogen‐bonded polymers were clearly demonstrated by differential scanning colorimetry, solid‐state NMR, and X‐ray powder diffraction analyses. The supramolecular behavior was also supported by fiber formation from the melt for several of these compounds, and stable glassy materials were prepared from the physical mixtures of two different biscaprolactams. The self‐association ability of ACL was also used by incorporating ACL at the chain ends of low‐molecular weight Jeffamine (M_n = 900 g/mol) using urea and amide linkages. The transformation of this liquid oligomer at room temperature into a self‐standing, transparent film clearly showed the improvement in mechanical properties obtained by the introduction of terminal hydrogen‐bonding groups. Finally, the use of monomers with a functionality of four gave rise to network formation either alone or combination with bifunctional monomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of lipooligosaccharides related to nodulation factors ofRhizobium sp. NGR234

Trisaccharide analogs of natural nodulation factors fromRhizobium sp. NGR234, namely, 2-acetamido-2-deoxy-4-O-(2-deoxy-2-hexadecanamido-β-d-glucopyranosyl)-6-O-(2-O-methyl-α-l-fucopyranosyl)-d-glucopyranose and its derivatives containing a 4-O-acetyl or a 3-O-sulfo group at thel-fucose residue, were synthesized. The oligosaccharides synthesized were shown to posses biological activity. Laboratoire de Biologie Moléculaire des Plantes Supérieures (LBMPS), Université de Genève, 1 ch. de l'Impératrice, 1292 Chambesy-Genève, Suisse. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya No. 3, pp. 513–518, March, 1998.     

Poly[μ3‐hydroxido‐μ6‐sulfato‐μ3‐(1,2,4‐triazolato‐κ3N1:N2:N4)‐dicadmium(II)]: a cadmium–triazolate coordination polymer with a pseudo‐cubane‐like tetranuclear cluster

The title complex, [Cd₂(C₂H₂N₃)(OH)(SO₄)]_n, is a three‐dimensional metal–organic framework consisting of pseudo‐cubane‐like tetranuclear cadmium clusters, which are formed by four Cd^II atoms, two sulfate groups and two hydroxide groups. The tetranuclear cadmium clusters are connected into a layered substructure by Cd—O bonds and adjacent layers are linked by triazolate ligands into a three‐dimensional network. A photoluminescent study revealed that the complex exhibits a strong emission in the visible region which probably originates from a π–π* transition.     

4‐Methylcarbazole‐3‐carboxylic acid

The title compound, C₁₄H₁₁NO₂, consists of a carbazole skeleton with carboxyl­ic acid and methyl groups at positions 3 and 4, respectively. Molecules are linked about inversion centres by O—H?O hydrogen bonds [O?O 2.620 (3) Å] to form centrosymmetric dimers.     

The Roots of Bio‐Molecular Simulation: The Eight‐Week CECAM Workshop ‘Models for Protein Dynamics’ of 1976

This year, the Centre Européen de Calcul Atomique et Moléculaire (CECAM) celebrates its 50‐th anniversary. Founded in 1969 in Orsay near Paris, it later moved to Lyon and in 2008 to Lausanne. It is an organization devoted to the promotion of fundamental research on advanced computational methods and their application in condensed matter science. Its main vehicle to this end is the organization of workshops. The key role of an eight‐week workshop held forty‐three years ago, characterized by an open exchange of scientific ideas and a foresight regarding the topics relevant to a proper dynamic simulation of bio‐molecules such as proteins, is remembered, together with the issues discussed at the time. These are still relevant today.     

A three‐dimensional polymeric potassium complex of 5‐sulfonobenzene‐1,2,4‐tricarboxylic acid: poly[μ‐aqua‐aqua‐μ9‐(2,4‐dicarboxy‐5‐sulfonatobenzoato)‐dipotassium(I)]

The asymmetric unit in the structure of the title compound, [K₂(C₉H₄O₉S)(H₂O)₂]_n, consists of two eight‐coordinated K^I cations, one 2,4‐dicarboxy‐5‐sulfonatobenzoate dianion (H₂SBTC²⁻), one bridging water molecule and one terminal coordinated water molecule. One K^I cation is coordinated by three carboxylate O atoms and three sulfonate O atoms from four H₂SBTC²⁻ ligands and by two bridging water molecules. The second K^I cation is coordinated by four sulfonate O atoms and three carboxylate O atoms from five H₂SBTC²⁻ ligands and by one terminal coordinated water molecule. The K^I cations are linked by sulfonate groups to give a one‐dimensional inorganic chain with cage‐like K₄(SO₃)₂ repeat units. These one‐dimensional chains are bridged by one of the carboxylic acid groups of the H₂SBTC²⁻ ligand to form a two‐dimensional layer, and these layers are further linked by the remaining carboxylate groups and the benzene rings of the H₂SBTC²⁻ ligands to generate a three‐dimensional framework. The compound displays a photoluminescent emission at 460 nm upon excitation at 358 nm. In addition, the thermal stability of the title compound has been studied.     

Co‐crystals of 3‐deoxy‐3‐fluoro‐α‐d‐glucopyranose and 3‐deoxy‐3‐fluoro‐β‐d‐glucopyranose

3‐Deoxy‐3‐fluoro‐d ‐glucopyranose crystallizes from acetone to give a unit cell containing two crystallographically independent molecules. One of these molecules (at site A) is structurally homogeneous and corresponds to 3‐deoxy‐3‐fluoro‐β‐d ‐glucopyranose, C₆H₁₁FO₅, (I). The second molecule (at site B) is structurally heterogeneous and corresponds to a mixture of (I) and 3‐deoxy‐3‐fluoro‐α‐d ‐glucopyranose, (II); treatment of the diffraction data using partial‐occupancy oxygen at the anomeric center gave a high‐quality packing model with an occupancy ratio of 0.84:0.16 for (II):(I) at site B. The mixture of α‐ and β‐anomers at site B appears to be accommodated in the lattice because hydrogen‐bonding partners are present to hydrogen bond to the anomeric OH group in either an axial or equatorial orientation. Cremer–Pople analysis of (I) and (II) shows the pyranosyl ring of (II) to be slightly more distorted than that of (I) [θ_(I) = 3.85 (15)° and θ_(II) = 6.35 (16)°], but the general direction of distortion is similar in both structures [ϕ_(I) = 67 (2)° (B_C1,C4) and ϕ_(II) = 26.0 (15)° (^C3TB_C1); B = boat conformation and TB = twist‐boat conformation]. The exocyclic hydroxymethyl (–CH₂OH) conformation is gg (gauche–gauche) (H5 anti to O6) in both (I) and (II). Structural comparisons of (I) and (II) to related unsubstituted, deoxy and fluorine‐substituted monosaccharides show that the gluco ring can assume a wide range of distorted chair structures in the crystalline state depending on ring substitution patterns.