A catalytic enantioselective synthesis of the antimelanoma marine natural product (-)-palmerolide A was accomplished using a longest sequence of 21 steps and without resorting to stoichiometric chiral auxiliaries or the chiral pool. The right half was constructed with a new variant of the Claisen-Ireland rearrangement exploiting an alkenylboronate as a masked hydroxyl. The left half featured the first application of a diol.SnCl(4)-catalyzed enantioselective crotylboration in the context of a complex target. This distinct strategy could pave the way to the design of simplified analogues of palmerolide.
In Every Direction
Chemical synthesis of proteins allowed the synthesis of ubiquitin chains modified in the vicinity of the isopeptide peptide to examine their behavior with deubiquitinases and ubiquitin binding domains. Our results set the ground for the generation of unique probes for studying the interactions of these chains with various ubiquitin-interacting proteins.
Aus allen Richtungen: Durch chemische Proteinsynthese wurden 14 Diubiquitin‐Analoga mit Modifikationen in der Umgebung der Isopeptidbindung hergestellt und auf ihr Verhalten gegenüber Deubiquitinasen und Ubiquitinbindedomänen untersucht. Die Ergebnisse schaffen die Grundlage für die Erzeugung von spezifischen Sonden zur Untersuchung der Wechselwirkungen dieser Ketten mit ubiquitinbindenden Proteinen.
a-D-Galacto-2-deoxy-oct-3-ulopyranosonic acids, a-Dgluco-2-deoxy-oct-3-ulopyranosonic acids and a-L-galacto-2,8-dideoxy-oct-3-ulopyranosonic acids can be converted into unnatural glycosyl amino acids via a one-pot intramolecular Ritter reaction. Initially, a ketopyranoside-based acid condenses under Lewis acid-promoted conditions with a nitrile (benzonitrile or acetonitrile) and a partially protected diamino ester (Boc-DAB-Ot-Bu, Boc-OrnOt-Bu) to form unnatural glycosyl amino esters. The resulting glycosyl amino esters are useful building blocks for solid-phase glycopeptide synthesis. For example, the glycosyl amino acid derived by condensation of a-D-galacto-2-deoxy-oct-3-ulopyranosonic acid with benzonitrile and DAB was used to replace serine in the potent opioid peptide sequence H 2 N-Tyr-D-Thr-Gly-Phe-Leu-Ser-CONH 2 .
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