Fluctuation-dissipation theorem and the dynamical renormalization group

The relation between a recently introduced dynamical real-space renormalization group and the fluctuation-dissipation theorem is discussed. An apparent incompatibility is pointed out and resolved.     

The lyconadins: enantioselective total syntheses of (+)-lyconadin A and (-)-lyconadin B

A full account of the enantioselective total syntheses of (+)-lyconadin A (1) and (-)-lyconadin B (2) is presented. Central to this venture was recognition and deployment of a key strategy-level intramolecular aldol/conjugate addition cascade that led, in a single operation, to two new carbon-carbon sigma-bonds, three new stereogenic centers, and two new rings, albeit with the incorrect stereogenicity at C(12) for the lyconadins. Correction of the C(12) stereogenicity was achieved via innovative use of a protonated intramolecular aminal. An aminoiodo olefin cyclization, in conjunction with alpha-pyridinone and 3,4-dihydropyridinone annulation protocols, permitted completion of the syntheses of (+)-lyconadin A (1) and (-)-lyconadin B (2), respectively.     

Total synthesis of (-)-aplaminal

The total synthesis and assignment of absolute configuration of (-)-aplaminal ( 1), a cytotoxic metabolite from a sea hare possessing a triazobicyclo[3.2.1]octane skeleton, has been achieved. The synthesis entailed condensation of a monoprotected diamine ( 3) with dimethyl 2-oxomalonate ( 4) to generate the imidazolidine core ( 2). Introduction of the third nitrogen via Mitsunobu activation and azide displacement, followed by reduction and lactam formation (AlMe 3), furnished (-)-aplaminal ( 1). Overall, the synthesis entailed 9 steps and proceeded in 19% overall yield.     

Copper-catalyzed synthesis of enantioenriched tetraarylethanes

Herein we report the asymmetric synthesis of 1,2-dipyridyl-1,2-diarylethanes via an unusual Cu(I)-catalyzed dimerization reaction. Subjection of a variety of enantioenriched substituted 2-pyridyl alcohols to a one-pot protocol generates the desired products in good yields and diastereoselectivities and with ee's up to >99%.     

A second-generation total synthesis of (+)-phorboxazole A.

A highly convergent second-generation synthesis of (+)-phorboxazole A has been achieved. Highlights of the synthetic approach include improved Petasis-Ferrier union/rearrangement conditions on a scale to assemble multigram quantities of the C(11-15) and C(22-26) cis-tetrahydropyrans inscribed with the phorboxazole architecture, a convenient method to prepare E- and Z-vinyl bromides from TMS-protected alkynes utilizing radical isomerization of Z-vinylsilanes, and a convergent late-stage Stille union to couple a fully elaborated C(1-28) macrocyclic iodide with a C(29-46) oxazole stannane side chain to establish the complete phorboxazole skeleton. The synthesis, achieved with a longest linear sequence of 24 steps, proceeded in 4.6% overall yield.     

Synthesis and biological evaluation of phorboxazole congeners leading to the discovery and preparative-scale synthesis of (+)-chlorophorboxazole a possessing picomolar human solid tumor cell growth inhibitory activity

Highly convergent syntheses of eight phorboxazole congeners and their evaluation against a diverse panel of human solid tumor cancer cell lines have been achieved. Specifically, the C(45-46) alkyne, alkene, and alkane phorboxazole A analogues [(+)-4-(+)-6] were constructed and found to display single digit nanomolar cell growth inhibitory activities in a series of human cancer cell lines. The structurally simplified C(11-15)-acetal congener (+)-20Z also proved potent albeit reduced (cf. 34.6 nM) when evaluated against the same cell line panel. Importantly, (+)-C(46)-chlorophorboxazole A (3) displayed picomolar (pM) inhibitory activity in several cell lines.     

Total synthesis of (+)-tedanolide

A convergent, stereocontrolled total synthesis of (+)-tedanolide (1), an architecturally complex marine antitumor macrolide, has been achieved in 31 steps (longest linear sequence). Highlights of the synthesis comprise a highly efficient dithiane union, followed by an Evans-Tishchenko "oxidation" to enable formation of the seco-ester in the presence of an oxidatively labile dithiane, a highly refined protecting group strategy, and a chemo- and stereoselective epoxidation at C(18,19).     

Analysis of the Electrochemical Oxidation of Multiwalled Carbon Nanotube Tower Electrodes in Sodium Hydroxide

Towers of aligned multiwalled carbon nanotubes (MWCNTs) were electrochemically oxidized in aqueous 1 M NaOH. An oxidation current that decayed with time was monitored using amperometry at a fixed potential. Cyclic voltammetry showed that the background current and electrode capacitance increased after oxidation without significantly affecting the faradaic current from the reduction of ferricyanide. Oxidation in NaOH caused morphological changes and increased hydrophilicity of the MWCNT tower electrodes. XPS spectra indicated increased oxygen on the surface after oxidation, while Raman spectra indicated that a large amount of amorphous carbon was present before and after oxidation.