Divergent Total Synthesis of the Antimitotic Agent Leiodermatolide

Subtle but distinctive: The stereostructure of the biologically highly promising antimitotic agent leiodermatolide was uncertain. A short, efficient, and flexible total synthesis based on ring-closing alkyne metathesis as the key step has now solved the puzzle. Subtle differences in the 1H NMR spectra of the structure shown and the conceivable isomer proved invaluable for the assignment

Synthesis, Molecular Editing, and Biological Assessment of the Potent Cytotoxin Leiodermatolide

It was by way of total synthesis that the issues concerning the stereostructure of leiodermatolide (1) have recently been solved; with the target now being unambiguously defined, the mission of synthesis changes as to secure a meaningful supply of this exceedingly scarce natural product derived from a deep-sea sponge. To this end, a scalable route of 19 steps (longest linear sequence) has been developed, which features a catalytic asymmetric propargylation of a highly enolizable β-keto-lactone, a ring closing alkyne metathesis and a modified Stille coupling as the key transformations. Deliberate digression from this robust blueprint brought a first set of analogues into reach, which allowed the lead qualities of 1 to be assessed. The acquired biodata show that 1 is a potent cytotoxin in human tumor cell proliferation assays, distinguished by GI50 values in the ≤3 nM range even for cell lines expressing the Pgp efflux transporter. Studies with human U2OS cells revealed that 1 causes mitotic arrest, micronucleus induction, centrosome amplification and tubulin disruption, even though no evidence for direct tubulin binding has been found in cell-free assays; moreover, the compound does not seem to act through kinase inhibition. Indirect evidence points at centrosome declustering as a possible mechanism of action, which provides a potentially rewarding outlook in that centrosome declustering agents hold promise of being inherently selective for malignant over healthy human tissue

Ultrafast electron and hole dynamics in novel conjugated star-shaped molecules

Charge dynamics in organic photovoltaic blends based on novel star-shaped molecules are studied by ultrafast visible-IR spectroscopy. Pathways of intra- and intermolecular electron and hole transfer and their recombination are identified and discussed

Ultrafast electron and hole dynamics in novel conjugated star-shaped molecules

Charge dynamics in organic photovoltaic blends based on novel starshaped molecules are studied by ultrafast visible-IR spectroscopy. Pathways of intra-and intermolecular electron and hole transfer and their recombination are identified and discussed

Effects of oligothiophene π-bridge length on physical and photovoltaic properties of star-shaped molecules for bulk heterojunction solar cells

The preparation of four different star-shaped donor (D)–π–acceptor (A) small molecules (N(Ph-1T-DCN-Me)3, N(Ph-2T-DCN-Me)3, N(Ph-2T-DCN-Hex)3 and N(Ph-3T-DCN-Hex)3) possessing various oligothiophene π-bridge lengths and their use in solution-processed bulk heterojunction small molecule solar cells is reported. Optical and electrochemical data show that increasing oligothiophene π-bridge length leads to a decrease of the optical band gap due to a parallel increase of the highest occupied molecular orbital (HOMO) level. Furthermore, subtle modifications of a molecular π-bridge length strongly affect the thermal behavior, solubility, crystallization, film morphology and charge carrier mobility, which in turn significantly change the device performance. Although the moderately increasing oligothiophene π-bridge length uplifts the HOMO level, it nevertheless induces an increase of the efficiency of the resulting solar cells due to a simultaneous improvement of the short circuit current (Jsc) and fill factor (FF). The study demonstrates that such an approach can represent an interesting tool for the effective modulation of the photovoltaic properties of the organic solar cells (OSCs) at a moderate cost