Aryl sulfonyl chlorides (e.g. Ts-Cl) are beloved of organic chemists as the most commonly used S(VI) electrophiles, and the parent sulfuryl chloride, O2 S(VI) Cl2 , has also been relied on to create sulfates and sulfamides. However, the desired halide substitution event is often defeated by destruction of the sulfur electrophile because the S(VI) Cl bond is exceedingly sensitive to reductive collapse yielding S(IV) species and Cl(-) . Fortunately, the use of sulfur(VI) fluorides (e.g., R-SO2 -F and SO2 F2 ) leaves only the substitution pathway open. As with most of click chemistry, many essential features of sulfur(VI) fluoride reactivity were discovered long ago in Germany.6a Surprisingly, this extraordinary work faded from view rather abruptly in the mid-20th century. Here we seek to revive it, along with John Hyatt's unnoticed 1979 full paper exposition on CH2 CH-SO2 -F, the most perfect Michael acceptor ever found.98 To this history we add several new observations, including that the otherwise very stable gas SO2 F2 has excellent reactivity under the right circumstances. We also show that proton or silicon centers can activate the exchange of SF bonds for SO bonds to make functional products, and that the sulfate connector is surprisingly stable toward hydrolysis. Applications of this controllable ligation chemistry to small molecules, polymers, and biomolecules are discussed.

High fidelity: 1‐Iodoalkynes react rapidly and selectively with organic azides in the presence of copper(I) catalysts (see scheme; TTTA=tris((1‐tert‐butyl‐1H‐1,2,3‐triazolyl)methyl)amine). The reaction is compatible with many functional groups and solvents, and 5‐iodotriazole products were usually obtained in excellent yield. These products can be further functionalized to give fully substituted 1,2,3‐triazoles.

Molecules that bind selectively to a given protein and then undergo a rapid chemoselective reaction to form a covalent conjugate have utility in drug development. Herein a library of 1,3,4-oxadiazoles substituted at the 2 position with an aryl sulfonyl fluoride and at the 5 position with a substituted aryl known to have high affinity for the inner thyroxine binding subsite of transthyretin (TTR) were conceived of by structure-based design principles and were chemically synthesized. When bound in the thyroxine binding site, most of the aryl sulfonyl fluorides react rapidly and chemoselectively with the pKa-perturbed K15 residue, kinetically stabilizing TTR and thus preventing amyloid fibril formation, known to cause polyneuropathy. Conjugation t50s range from 1 to 4 min, ~ 1400 times faster than the hydrolysis reaction outside the thyroxine binding site. X-ray crystallography confirms the anticipated binding orientation and sheds light on the sulfonyl fluoride activation leading to the sulfonamide linkage to TTR. A few of the aryl sulfonyl fluorides efficiently form conjugates with TTR in plasma. A few of the TTR covalent kinetic stabilizers synthesized exhibit fluorescence upon conjugation and therefore could have imaging applications as a consequence of the environment sensitive fluorescence of the chromophore.

The translation of biological glycosylation in humans to the clinical applications involves systematic studies using homogeneous samples of oligosaccharides and glycoconjugates, which could be accessed by chemical, enzymatic or other biological methods. However, the structural complexity and wide-range variations of glycans and their conjugates represent a major challenge in the synthesis of this class of biomolecules. To help navigate within many methods of oligosaccharide synthesis, this Perspective offers a critical assessment of the most promising synthetic strategies with an eye on the therapeutically relevant targets.

Glycoscience research has been significantly impeded by the complex compositions of the glycans present in biological molecules and the lack of convenient tools suitable for studying the glycosylation process and its function. Polysaccharides and glycoconjugates are not encoded directly by genes; instead, their biosynthesis relies on the differential expression of carbohydrate enzymes, resulting in heterogeneous mixtures of glycoforms, each with a distinct physiological activity. Access to well-defined structures is required for functional study, and this has been provided by chemical and enzymatic synthesis and by the engineering of glycosylation pathways. This review covers general methods for preparing glycans commonly found in mammalian systems and applying them to the synthesis of therapeutically significant glycoconjugates (glycosaminoglycans, glycoproteins, glycolipids, glycosylphosphatidylinositol-anchored proteins) and the development of carbohydrate-based vaccines.

Arylsulfonylchloride (z. B. Ts‐Cl) sind die am häufigsten eingesetzten SVI‐Elektrophile in der organischen Synthesechemie, und auch die Stammverbindung, das Sulfurylchlorid (O2SVICl2), wurde zur Synthese von Sulfaten und Sulfamiden genutzt. Allerdings wird die gewünschte Halogenidsubstitution oftmals durch die Zersetzung des Schwefelelektrophils in SIV‐Spezies und Cl− verhindert, denn die SVI‐Cl‐Bindung ist äußerst reduktionsanfällig. Mit Schwefel(VI)‐fluoriden (z. B. R‐SO2‐F und SO2F2) verläuft die Umsetzung hingegen ausschließlich über den Substitutionsweg. Wie es bei der Click‐Chemie zumeist der Fall ist, wurden viele entscheidende Aspekte der Reaktivität von Schwefel(VI)‐fluoriden vor langer Zeit in Deutschland entdeckt.6a Überraschenderweise gerieten diese außerordentlichen Arbeiten in der Mitte des 20. Jahrhunderts ziemlich abrupt aus dem Blickfeld. In diesem Aufsatz versuchen wir, dieser Chemie neues Leben einzuhauchen. Insbesondere stützen wir uns dabei auch auf John Hyatts unbeachtet gebliebene Veröffentlichung über CH2CH‐SO2‐F aus dem Jahr 1979.98 Wir tragen mehrere neue Beobachtungen bei, einschließlich dem Befund, dass das ansonsten sehr stabile Gas SO2F2 eine exzellente Reaktivität unter den richtigen Umständen aufweist. Wir zeigen auch, dass Protonen oder Siliciumzentren den Austausch von S‐F‐Bindungen gegen S‐O‐Bindungen aktivieren können und dass der Sulfat‐Konnektor überraschend hydrolysestabil ist. Anwendungen dieser kontrollierbaren Ligationschemie auf kleine Moleküle, Polymere und Biomoleküle werden diskutiert.

Fluorinated glycosides are known to resist the glycosidase-catalyzed glycosidic bond cleavage; however, the synthesis of such glycans, especially 3-fluoro-sialic acid (3F-Neu5Ac) containing sialosides, has been a major challenge. Though the enzymatic synthesis of α-2,3-linked 3F-sialosides was reported, until recently there has not been any effective method available for the synthesis of 3F-sialosides in the α-2,6-linkage. In order to understand the biological effect of such modification, we report here a chemical synthesis of 3Fax-Neu5Ac-α2,6-Gal as a building block for the assembly of 3Fax-Neu5Ac-containing sialosides and a representative homogeneous antibody glycoform. Our results showed that the sialosides are stable under sialidase catalysis and the rituximab glycoform with a sialylated complex-type biantennary glycan terminated with 3Fax-Neu5Ac in the α-2,6-linkage (α2,6-F-SCT) has a similar binding avidity as its parent glycoform. These findings open up new opportunities for the development of therapeutic glycoproteins with improved pharmacokinetic parameters.

Sauber verklebt: 1‐Iodalkine reagieren schnell und selektiv mit organischen Aziden in Gegenwart von Kupfer(I)‐Katalysatoren [siehe Schema; TTTA=Tris((1‐tert‐butyl‐1H‐1,2,3‐triazolyl)methyl)amin]. Viele funktionelle Gruppen und Lösungsmittel können verwendet werden, und die 5‐Iodtriazole, die in sehr guten Ausbeuten entstehen, lassen sich gut zu vollständig substituierten 1,2,3‐Triazolen funktionalisieren.