Many essential biological processes are controlled by posttranslational protein modifications. The inability to synthetically attain the diversity enabled by these modifications limits functional studies of many proteins. We designed a three-step approach for installing authentic posttranslational modifications in recombinant proteins. We first use the established O-phosphoserine (Sep) orthogonal translation system to create a Sep-containing recombinant protein. The Sep residue is then dephosphorylated to dehydroalanine (Dha). Last, conjugate addition of alkyl iodides to Dha, promoted by zinc and copper, enables chemoselective carbon-carbon bond formation. To validate our approach, we produced histone H3, ubiquitin, and green fluorescent protein variants with site-specific modifications, including different methylations of H3K79. The methylated histones stimulate transcription through histone acetylation. This approach offers a powerful tool to engineer diverse designer proteins.

DJ‐1 family proteins have recently been characterized as novel glyoxalases, although their cofactor‐free catalytic mechanisms are not fully understood. Here, we obtained crystals of Arabidopsis thaliana DJ‐1d (atDJ‐1d) and Homo sapiens DJ‐1 (hDJ‐1) covalently bound to glyoxylate, an analog of methylglyoxal, forming a hemithioacetal that presumably mimics an intermediate structure in catalysis of methylglyoxal to lactate. The deuteration level of lactate supported the proton transfer mechanism in the enzyme reaction. Differences in the enantiomeric specificity of d/l‐lactacte formation observed for the DJ‐1 superfamily proteins are explained by the presence of a His residue in the active site with essential Cys and Glu residues. The model for the stereospecificity was further evaluated by a molecular modeling simulation with methylglyoxal hemithioacetal superimposed on the glyoxylate hemithioacetal. The mechanism of DJ‐1 glyoxalase provides a basis for understanding the His residue‐based stereospecificity. Database Structural data have been submitted to the Protein Data Bank under accession numbers http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4OFW (structure of atDJ‐1d), http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4OGF (structure of hDJ‐1 with glyoxylate) and http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4OGG (structure of atDJ‐1d with glyoxylate).

The carbonyl group occupies a position of central importance in organic synthesis as it allows ready functionalization, for example, in the a, b, and g positions. Direct transformations into other versatile functional groups, such as alkenes and epoxides, further increase the importance of carbonyl groups in synthesis. The ability to conduct such transformations enantioselectively would be extremely useful, and toward this goal we recently reported a practical, catalytic, and asymmetric conversion of aldehydes into epoxides by using the sulfide 1 (Scheme 1).[1] The sulfide 1, which is readily available in both enantiomeric forms, was obtained in four steps in 48 % overall yield from camphorsulfonyl chloride.However, attempts to apply our catalytic process to the synthesis of CDP-840, through an epoxidation reaction with 4-pyridinecarboxaldehyde, were unsuccessful. In mapping out the scope of the catalytic process we discovered that, as well as the reactions of heteroaromatic aldehydes that bear basic groups, those of n-alkyl aliphatic aldehydes, a,b-unsaturated aldehydes, acetylenic aldehydes, and ketones gave either low yields, low diastereomeric ratios, or low enantioselectivities. [2] A further limitation of the catalytic process emerged when we attempted to use a,b-unsaturated hydrazones with the chiral sulfide 1, as only low yields were observed. As unsaturated epoxides [3] and epoxides that contain a basic nitrogen functionality are difficult to prepare by oxidative methods, we were keen to find a solution to this problem. Indeed, a common limitation in catalytic asymmetric synthesis is substrate specificity and one solution to the problem is to devise a stoichiometric process with good recovery of the chirality-transfer agent. An outstanding example is the Evans auxiliary, which, even though it is used in stoichiometric amounts, is widely employed as a result of its broad applicability, reliability, and recyclability. Although enantioselective epoxidations with stoichiometric quantities of sulfide have been described, their scope is limited. SolladiØ-Cavallo et al. have only described the reaction of Eliel's oxathiane benzyl sulfonium salt with aromatic, [4] heteroaromatic, [5] and a,b-unsaturated aldehydes.[6] Metzner and coworkers have reported moderate to high enantioselectivities in reactions of trans-2,5-dimethylthiolane benzyl sulfonium salt with aromatic and heteroaromatic aldehydes [7] and moderate enantioselectivities in related allyl sulfonium salt reactions.[8] Furthermore, it is not possible to access both enantiomers of these sulfides easily, which further limits their practical applications.Herein we describe a process for the epoxidation of a very broad range of carbonyl compounds, including ketones, in high yields and with high selectivities. Although stoichiometric quantities of sulfide were required, the resulting high Scheme 1. Catalytic and asymmetric epoxidation of aldehydes; conditions: Rh 2 (OAc) 4 (1 mol %), BnEt 3 N + Cl À (10 mol %), CH 3 CN, 40 8C.[*] Prof.

Presented here is a concise synthesis of secu′amamine A, and fluvirosaones A and B from readily available allosecurinine and viroallosecurinine. The key C2‐enamine derivative of (viro)allosecurinine, the presumed biosynthetic precursors of these natural products, was accessed, for the first time, by a VO(acac)2‐mediated regioselective Polonovski reaction. Formal hydration and 1,2‐amine shift of this pluripotent enamine compound afforded secu′amamine A. Formal oxidative [3+2] cycloaddition reaction between this enamine and TMS‐substituted methallyl iodide reagent paved the way to the precursors of fluvirosaones A and B. The relative stereochemistry at the C2 position of these advanced intermediates governs the fate of 1,2‐amine shift leading to fluvirosaones A and B. The syntheses of potential biosynthetic precursors and investigations of their chemical reactivities have provided insights regarding the biogenesis of these natural products.

The first total synthesis of waihoensene, a tetracyclic diterpene containing an angular triquinane and a six-membered ring, with four contiguous quaternary carbon atoms, was achieved through the tandem cycloaddition reaction of an allenyl diazo substrate containing a six-membered ring via trimethylenemethane (TMM) diyl intermediate.