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1,4-Bis(hex-yloxy)-2,5-diiodo-benzene

2010, Thevenet, Damien, Neier, Reinhard, Sereda, Olha, Neels, Antonia, Stoeckli-Evans, Helen

The centrosymmetric title compound, C(18)H(28)I(2)O(2), crystallized in the monoclinic space group P2(1)/c with the alkyl chains having extended all-trans conformations, similar to those in the centrosymmetric bromo analogue [Li et al. (2008 (black right triangle)). Acta Cryst. E64, o1930] that crystallized in the triclinic space group P. The difference between the two structures lies in the orientation of the two alkyl chains with respect to the C(aromatic)-O bond. In the title compound, the O-C(alk-yl)-C(alk-yl)-C(alk-yl) torsion angle is 55.8 (5)°, while in the bromo analogue this angle is -179.1 (2)°. In the title compound, the C-atoms of the alkyl chain are almost coplanar [maximum deviation of 0.052 (5) Å] and this mean plane is inclined to the benzene ring by 50.3 (3)°. In the bromo-analogue, these two mean planes are almost coplanar, making a dihedral angle of 4.1 (2)°. Another difference between the crystal structures of the two compounds is that in the title compound there are no halide(midline ellipsis)halide inter-actions. Instead, symmetry-related mol-ecules are linked via C-H(midline ellipsis)? contacts, forming a two-dimensional network.

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The synthesis of a pyrazol analogon of porphobilinogen with the help of the Mukaiyama aldol reaction

2003, Chaperon, André, Bertschy, Hugo, Franz-schrumpf, Anne-laurence, Hugelet, Bertrand, Neels, Antonia, Stoeckli-Evans, Helen, Neier, Reinhard

The synthesis of a pyrazol analogon of porphobilinogen is described. The Mukaiyama crossed aldol reaction is the key step of our approach. The retrosynthetic anal. follows the mechanism for the biosynthesis of porphobilinogen initially proposed by Shemin. [on SciFinder(R)]

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A Chemical Synthesis of Porphobilinogen Imitating the Pathway Proposed by Shemin for the Biosynthesis: Comparing Inhibtion Studies with Investigations of Chemical Reality

1998, Bobal, Pavel, Chaperon, André, Neels, Antonia, Stoeckli-Evans, Helen, Neier, Reinhard

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1,4-Bis(hexyloxy)-2,5-diiodobenzene

2010, Thevenet, Damien, Neier, Reinhard, Sereda, Olha, Neels, Antonia, Stoeckli-Evans, Helen

The centrosym. title compd., C18H28I2O2, crystd. in the monoclinic space group P21/c with the alkyl chains having extended all-trans conformations, similar to those in the centrosym. bromo analog that crystd. in the triclinic space group P?1. The difference between the 2 structures lies in the orientation of the 2 alkyl chains with respect to the C(arom.)-O bond. In the title compd., the O-Calkyl-Calkyl-Calkyl torsion angle is 55.8(5)°, while in the bromo analog this angle is -179.1(2)°. In the title compd., the C-atoms of the alkyl chain are almost coplanar [max. deviation of 0.052(5) Å] and this mean plane is inclined to the benzene ring by 50.3(3)°. In the bromo-analog, these 2 mean planes are almost coplanar, making a dihedral angle of 4.1(2)°. Another difference between the crystal structures of the 2 compds. is that in the title compd. there are no halide...halide interactions. Instead, symmetry-related mols. are linked via C-H...? contacts, forming a 2D network. Crystal data: monoclinic, P21/n, a = 9.441(9), b = 7.8455(6), c = 13.457(2) Å, ? = 92.148(12)°, Z = 2, 1216 obsd. reflections with I > 2(I), 101 refined parameters, R[F2 > 2?(F2)] = 0.029, wR(F2) = 0.055. [on SciFinder(R)]

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The novel sequence Diels-Alder reaction/Ireland-Claisen rearrangement applied to acyclic dienophiles: New insights into the selectivity of the Ireland-Claisen rearrangement

1999-1-12, Velker, Joerg, Roblin, Jean Philippe, Neels, Antonia, Tesouro, Ana, Stoeckli-Evans, Helen, Klaerner, Frank-Gerrit, Gehrke, Jan-Stefan, Neier, Reinhard

The new dienes 4a-d, 7 and 11 reacted in good yields with acyclic dienophiles like methyl acrylate and diethyl fumarate in the tandem process Diels-Alder reaction/Ireland-Claisen rearrangement. Analysis of the relative configuration of products 5, 6, 8-10 and 12 indicated that preference for the chair or boat transition state of the Ireland-Claisen rearrangement is strongly influenced by the relative configuration of the substituents of the cyclohexene ring.

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The high stereoselectivity of the tandem sequence Diels-Alder reaction/Ireland-Claisen rearrangement starting from substituted O-(E)-buta-1,3-dienyl ketene acetals and cyclic dienophiles

2007, Soldermann, Nicolas, Velker, Joerg, Neels, Antonia, Stoeckli-Evans, Helen, Neier, Reinhard

A new tandem reaction leads to bicyclic cyclohexene derivs., e. g. I, with complete control of the relative configuration of the four chiral centers formed. The high diastereoselectivity is the consequence of an endo-selective Diels-Alder reaction followed by an Ireland-Claisen rearrangement that proceeds via a boat-like transition state. [on SciFinder(R)]

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A chemical synthesis of porphobilinogen imitating the pathway proposed by Shemin for the biosynthesis: comparing inhibition studies with investigations of chemical reactivity

1999, Bobal, Pavel, Chaperon, André, Neels, Antonia, Stoeckli-Evans, Helen, Neier, Reinhard

The synthesis of porphobilinogen and related compds. was reviewed with 78 refs. in this conference proceeding. Nature's pathways have been a strong motivation for synthetic chemists. Trying to imitate what has been shown or what is supposed to be a biosynthetic transformation always pursues several objectives: One evident goal is to obtain the natural product via the elegant way used in the natural process. The second not less important goal is to obtain insight into the mechanistic details of the biosynthetic pathway. Finally during the synthetic effort compds. are obtained which are potentially interesting as inhibitors of the natural process. Porphobilinogen, the second dedicated intermediate in the biosynthesis of 'pigments of life' synthesized following the mechanistic rationale proposed 30 yr ago by Shemin for the biosynthesis. Substances obtained during this synthetic effort and inhibitors esp. synthesized for our studies were tested in order to evaluate the different mechanistic proposals. This biomimetic approach allowed to guide at the same time the synthetic as well as the biosynthetic studies. [on SciFinder(R)]