Tore Bonge-Hansen

Microporous Molecular Materials from Dipeptides Containing Non-proteinogenic Residues

Dipeptides with two hydrophobic side chains have proved to be an exceptional source of microporous organic materials, but since previous structures were limited to the incorporation of only proteinogenic residues, their full potential as adsorbents has remained unexplored. Single-crystal XRD data for ten new compounds with non-proteinogenic L-2-aminobutanoic acid and/or L-2-amino-pentanoic acid are presented. The gas-phase accessibility of their crystal pores, with cross-sections of 2.3 to 5.1 Å, was monitored by CO2 and CH4 adsorption isotherms. Included CO2 was also detected spectroscopically by 2D MAS NMR. An extensive conformational analysis reveals that the use of linear rather than branched side chains (such as L-valine and L-isoleucine) affords peptides with a greater degree of conformational freedom and yields more-flexible channel surfaces that may easily adapt to a series of potential guest molecules.

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

Summary In this work, we introduce a new class of halodiazocarbonyl compounds, α-halodiazoacetamides, which through a metal-free, ambient-temperature thermolysis perform intramolecular C–H insertions to produce α-halo-β-lactams. When carried out with α-bromodiazoacetamides bearing cyclic side chains, the thermolysis reaction affords bicyclic α-halo-β-lactams, in some cases in excellent yields, depending on the ring size and substitution pattern of the cyclic amide side chains.

Nucleophilic Halogenations of Diazo Compounds, a Complementary Principle for the Synthesis of Halodiazo Compounds: Experimental and Theoretical Studies

Three new protocols for the nucleophilic halogenations of diazoesters, diazophosphonates, and diazopiperidinylamides as complementary methods to our previously reported electrophilic halogenations are presented for the first time. On the basis of hypervalent α-aryliodonio diazo triflate salts 1A, 2A, and 3A, the corresponding halodiazo compounds are generated via nucleophilic halogenations with tetrabutylammonium halides or potassium halides. The products from subsequent catalytic intermolecular cyclopropanations of the halodiazoesters and halodiazophosphonates and thermal intramolecular C-H insertion of the brominated diazopiperidinylamide are obtained in moderate to good yields after two steps. DFT calculations are presented for the diazoesters to give insight into the mechanism and transition states of the nucleophilic substitutions with the neutral nucleophiles dimethyl sulfide and triethylamine and the bromination with Br(-).

Synthesis of quinoline-3-carboxylates by a Rh(II)-catalyzed cyclopropanation-ring expansion reaction of indoles with halodiazoacetates

Summary In this letter, we report a novel synthesis of ethyl quinoline-3-carboxylates from reactions between a series of indoles and halodiazoacetates. The formation of the quinoline structure is probably the result of a cyclopropanation at the 2- and 3-positions of the indole followed by ring-opening of the cyclopropane and elimination of H–X.

Stereoselectivity through a network of non-classical CH weak interactions: a prospective study of a bicyclic organocatalytic scaffold

A prospective novel organocatalyst scaffold has been investigated by computational studies for its potential to induce stereoselective reactions. Density functional theory calculations (DFT) of an organocatalysed Diels–Alder reaction between cinnamaldehyde and cyclopentadiene, show that it is possible to induce selectivity by placing appropriate chemical groups on the scaffold. In the present case small substituents with strong electronic effects are found to be more effective in controlling the stereochemical induction than sterically bulky substituents. We show, using noncovalent interaction analysis (NCI plots), that the CF3 group is especially efficient in improving the stereochemical control as well as increasing the reaction rate.

A solid-state oxidation of 1,1,3,3-tetramethylguanidinium 4-methylbenzenesulfinate to 1,1,3,3-tetramethylguanidinium 4-methylbenzenesulfonate.

The organic acid-base complex 1,1,3,3-tetramethylguanidinium 4-methylbenzenesulfonate, C5H14N3(+)·C7H7O3S(-), was obtained from the corresponding 1,1,3,3-tetramethylguanidinium 4-methylbenzenesulfinate complex, C5H14N3(+)·C7H7O2S(-), by solid-state oxidation in air. Comparison of the two crystal structures reveals similar packing arrangements in the monoclinic space group P2(1)/c, with centrosymmetric 2:2 tetramers being connected by four strong N-H···O=S hydrogen bonds between the imine N atoms of two 1,1,3,3-tetramethylguanidinium bases and the O atoms of two acid molecules.

Total synthesis and antileukemic evaluations of the phenazine 5,10-dioxide natural products iodinin, myxin and their derivatives

A new efficient total synthesis of the phenazine 5,10-dioxide natural products iodinin and myxin and new compounds derived from them was achieved in few steps, a key-step being 1,6-dihydroxyphenazine di-N-oxidation. Analogues prepared from iodinin, including myxin and 2-ethoxy-2-oxoethoxy derivatives, had fully retained cytotoxic effect against human cancer cells (MOLM-13 leukemia) at atmospheric and low oxygen level. Moreover, iodinin was for the first time shown to be hypoxia selective. The structure-activity relationship for leukemia cell death induction revealed that the level of N-oxide functionality was essential for cytotoxicity. It also revealed that only one of the two phenolic functions is required for activity, allowing the other one to be modified without loss of potency.

On the cause of low thermal stability of ethyl halodiazoacetates

Summary Rates for the thermal decomposition of ethyl halodiazoacetates (halo = Cl, Br, I) have been obtained, and reported herein are their half-lives. The experimental results are supported by DFT calculations, and we provide a possible explanation for the reduced thermal stability of ethyl halodiazoacetates compared to ethyl diazoacetate and for the relative decomposition rates between the chloro, bromo and iodo analogs. We have also briefly studied the thermal, non-catalytic cyclopropanation of styrenes and compared the results to the analogous Rh(II)-catalyzed reactions.

Frontispiece: Microporous Molecular Materials from Dipeptides Containing Non‐proteinogenic Residues

Microporous Materials In their Communication on page 15684 ff., C. H. Görbitz and co-workers report that dipeptides containing non-proteinogenic residues form crystals with open channels, the diameter of which is tuned by the bulk of the non-proteinogenic units.

1,4-Bis(2-diazo­acet­yl)piperazine

The asymmetric unit of the title compound, C8H10N6O2, contains one-half molecule, which is completed by a crystallographic center of symmetry. The piperazine ring adopts a chair conformation. In the crystal, weak C—H⋯O interactions link the molecules into layers parallel to the bc plane. The crystal packing also exhibits short N⋯N contacts of 3.0467 (16) Å between the terminal diazo N atoms from neighbouring molecules.