The first synthesis of substituted fluorenones directly from benzaldehydes and aryl iodides via a Pd(II)-catalyzed C(sp)-H functionalization cascade is reported. Featuring anthranilic acid as an inexpensive transient directing group, the process is compatible with a variety of benzaldehydes and aryl iodides. A three-step synthesis of the antiviral drug Tilorone was completed in an excellent overall yield (40%), demonstrating the utility of this method.
Integration by parts: advanced information processing at the molecular level requires integrated logic gates, which has to date been possible only virtually. Now, two independently working AND molecular logic gates are brought together by "click" chemistry to form integrated logic gates which respond exactly as predicted from such an integration scheme.
Oxalyl-tethered pyrroles can be doubly bridged with two difluoroboron chelating units to yield bright orange dyes. Interestingly, in polar organic solvents, the addition of fluoride and cyanide result in reversible detachment of the otherwise stable difluoroboron bridges, resulting in sharp changes in color. Thus, this novel compound behaves as a highly selective chromogenic sensor for fluoride and cyanide ions.
Studies on the biosynthesis of glycopeptide antibiotics have provided many insights into the strategies that Nature employs to build architecturally strained molecules. A key structural feature of vancomycin, the founding member of this class, is a set of three aromatic cross-links that are introduced via yet unknown mechanisms. Previous reports have identified three cytochrome P450 enzymes involved in this process and demonstrated enzymatic activity for OxyB, which installs the first aromatic cross-link. However, the activities of the remaining two P450 enzymes have not been recapitulated. Herein, we show that OxyA generates the second bis-aryl ether bond in vancomycin and that it exhibits strict substrate specificity toward the chlorinated, OxyB-cross-linked product. No OxyA product is detected with the unchlorinated substrate. Together with previous results, these data suggest that chlorination occurs after OxyB- but before OxyA-catalyzed cross-link formation. Our results have important implications for the chemo-enzymatic synthesis of vancomycin and its analogs.
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