Evolved,Selective Erasers of Distinct Lysine Acylations

Lysine acylations, a family of diverse protein modifications varying in acyl‐group length, charge, and saturation, are linked to many important physiological processes. Only a small set of substrate‐promiscuous lysine acetyltransferases and deacetylases (KDACs) install and remove this vast variety of modifications. Engineered KDACs that remove only one type of acylation would help to dissect the different contributions of distinct acylations. We developed a bacterial selection system for the directed evolution of KDACs and identified variants up to 400 times more selective for butyryl‐lysine compared to crotonyl‐lysine. Structural analyses revealed that the enzyme adopts different conformational states depending on the type of acylation of the bound peptide. We used the butyryl‐selective KDAC variant to shift the cellular acylation spectrum towards increased lysine crotonylation. These new enzymes will help in dissecting the roles of different lysine acylations in cell physiology.     

Concise Total Syntheses of Amphidinolides C and F

The marine natural products amphidinolide C ( 1 ) and F ( 4 ) differ in their side chains but share a common macrolide core with a signature 1,4‐diketone substructure. This particular motif inspired a synthesis plan predicating a late‐stage formation of this non‐consonant (“umpoled”) pattern by a platinum‐catalyzed transannular hydroalkoxylation of a cycloalkyne precursor. This key intermediate was assembled from three building blocks ( 29 , 41 and 47 (or 65 )) by Yamaguchi esterification, Stille cross‐coupling and a macrocyclization by ring‐closing alkyne metathesis (RCAM). This approach illustrates the exquisite alkynophilicity of the catalysts chosen for the RCAM and alkyne hydroalkoxylation steps, which activate triple bonds with remarkable ease but left up to five other π‐systems in the respective substrates intact. Interestingly, the inverse chemoselectivity pattern was exploited for the preparation of the tetrahydrofuran building blocks 47 and 65 carrying the different side chains of the two target macrolides. These fragments derive from a common aldehyde precursor 46 formed by an exquisitely alkene‐selective cobalt‐catalyzed oxidative cyclization of the diunsaturated alcohol 44 , which left an adjacent acetylene group untouched. The northern sector 29 was prepared by a two‐directional Marshall propargylation strategy, whereas the highly adorned acid subunit 41 derives from D ‐glutamic acid by an intramolecular oxa‐Michael addition and a proline‐mediated hydroxyacetone aldol reaction as the key steps; the necessary Me₃Sn‐group on the terminus of 41 for use in the Stille coupling was installed via enol triflate 39 , which was obtained by selective deprotonation/triflation of the ketone site of the precursor 38 without competing enolization of the ester also present in this particular substrate.     

Synthesis of 1,5-Dimethoxy-4-naphthol and 2-Allyl-5-methoxy-1,4-Naphthoquinone A New Approach

Convenient syntheses for 1,5-dimethoxy-4-naphthol and 2-allyl-5-methoxy-1,4-naphthoquinone have been developed. A key step in the formation of the title compounds involved methylation or allylation of an intermediate Diels-Alder adduct.