Ikuo Ueda

Cycloaromatization of a non-conjugated polyenyne system: Synthesis of 5H-benzo[d]fluoreno[3,2-b]pyrans via diradicals generated from 1-[2-{4-(2-alkoxymethylphenyl)butan-1,3-diynyl}]phenylpentan-2,4-diyn-1-ols and trapping evidence for the 1,2-didehydrobenzene diradical

Non-conjugated tetraynes 1 undergo thermal intramolecular cyclization to non-benzenoid diradicals (23) followed by radical cycloaromatization at 25 °C to provide 7-dehydro-5H-benzo[d]fluoreno[3,2-b]pyran monoradical (24) and alkyl radicals (25). Hydrogen abstraction of 24 gives 5H-benzo[d]fluoreno[3,2-b]pyrans (3) which are converted to 4 by reaction with 25. On the other hand, 2 gives 5H-fluorenol (5), indicating the formation of 1,2-didehydrobenzene diradical intermediates (28 and 29). These radicals are trapped as the corresponding Diels-Alder-type products by reaction with an aromatic diene, anthracene.

Synthesis, structure and properties of 3,9,15-tri- and 3,6,9,12,15,18-hexasubstituted dodecadehydro[18]annulenes (C18H3R3 and C18R6) with D6h-symmetry

Abstract 3,9,15-Tris(p-tert-butylphenyl)dodecadehydro[18]annulene (6) and 3,6,9,12,15,18-hexa-substituted dodecadehydro[18]annulenes (7, 8, and 9) have been prepared. These compounds were shown to be heated up to 150 °C without decomposition. The molecular structure of 7 was determined by X-ray crystallography, which showed that 7 has a planar π-system with D6h-symmetry. The UV and NMR spectral data indicate that the four compounds have high thermal and conformational stability and a strong diamagnetic induced ring-current.

Synthesis of the first 3,6,9,15,18,18-hexa-substituted-1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydro[18]annulenes with D6h-symmetry

Abstract 3,6,9,12,15,18-Hexaphenyl-1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydro[18]annulene and related compounds have been synthesized. These compounds were found to be stable both in crystalline forms and chloroform solution at room temperature, to have aromatic character by the existance of a diamagnetic ring current on the basis of the nmr spectral data, and to conform to the D 6h -symmetry group.

Domino thermal radical cycloaromatization of non-conjugated aromatic hexa- and heptaynes: synthesis of fluoranthene and benzo[a]rubicene skeletons

Non-conjugated aromatic hexa- and heptaynes underwent domino thermal radical cycloaromatization at 25°C to yield indenol ring-fused fluoranthene and indenol ring-fused benzo[a]rubicene skeletons with helicity. This multi-cyclization reaction proceeded regioselectively to yield [6]helicene derivatives via annulation at the final step. The structure and thermal racemization of [6]helicene derivatives (6 and 7) is also described.

Multiple cycloaromatization of novel aromatic enediynes bearing a triggering device on the terminal acetylene carbon

Abstract Aromatic enediynes (1) bearing a triggering device on the terminal acetylene carbon undergo thermal cyclization at 25 °C to yield polyphenylene ring systems (6, 9, 13, and 15(16)) giving radical intermediates, dehydrobenzene monoradical (12) and didehydrobenzene biradicals (4 and 14) which may serve as a DNA-cleaving reagent.

An unprecedented arylcarbene formation in thermal reaction of non-conjugated aromatic enetetraynes and DNA strand cleavage

The thermal cyclization of non-conjugated aromatic enetetrayne (4) led to the final products (2 and 10) affording 5 H-12-hydroxybenzo[d]fluoreno[3,2-b]pyran radical (C) and arylcarbene (D) intermediates. DNA strand cleavage was observed.

Synthesis and reactivity of a new designed molecule, 6,7-benzobicyclo[8.3.0]trideca-1,6,10-triene-3,8-diyn-5-one as a pharmacophore of the enediyne antitumor agents

Abstract A new designed tetradehydro[10]annulene quinomethide analogue 1 , which is a simplified analogue having combined structural features of neocarzinostatin chromophore and golfomycin A, was prepared. Cycloaromatization of 1 and Micheal-type addition of thiol to 16 which is a precursor of 1 , were also demonstrated.

A Biological Molecular Motor, Proton-Translocating ATP Synthase: Multidisciplinary Approach for a Unique Membrane Enzyme

Proton-translocating ATP synthase (FoF1) synthesizes ATP from ADP and phosphate, coupled with an electrochemical proton gradient across the biological membrane. It has been established that the rotation of a subunit assembly is an essential feature of the enzyme mechanism and that FoF1 can be regarded as a molecular motor. Thus, experimentally, in the reverse direction (ATP hydrolysis), the chemical reaction drives the rotation of a γεc10-14 subunit assembly followed by proton translocation. We discuss our very recent results regarding subunit rotation in Escherichia coli FoF1 with a combined biophysical and mutational approach.

Synthesis and DNA cleaving activity of water-soluble non-conjugated thienyl tetraynes.

Water-soluble non-conjugated thienyl tetraynes (3-6) were synthesized and their DNA cleaving activity was evaluated using electrophoresis, atomic force microscopy (AFM) and Escherichia coli (E. coli) transformation techniques. The amino-functionalized compound 4 was shown to possess an activity to cleave plasmid DNA by both electrophoresis and E. coli transformation techniques. AFM also showed a cleavage of the circular DNA into a linear form with a formation of burst-star-shaped architectures, which were envisaged to be cross-linked DNA oligomers.

Cyclopentenones from 2-ethoxyallylidene(triphenyl)phosphorane and 1,2-diacylethylenes: Synthesis of (±)-methyl dehydrojasmonate

Abstract (3-(Alkoxycarbonyl)-2-ethoxy-2-propenylidene)triphenylphosphorane reacted with diacylethylenes to give 2-ethoxycyclopentadienes as a 1:1 mixture of the 1,3- and 1,4-dienes, which were converted upon mild acid treatment into cyclopentenones in a single form. Use of acylmethylenemalonate as an unsymmetrical substrate provides an excellent route to substituted cyclopentenones. An application of the annulation to synthesis of (±)-methyl dehydrojasmonate is also described.