Copyright © 2019 American Chemical Society. A Rh-catalyzed asymmetric intramolecular Buchner ring expansion of α-alkyl-α-diazoesters has been developed. The present protocol generates a 5,7-fused ring system in an enantioselective manner while minimizing β-hydrogen migration, which has been a competing reaction when using α-alkyl-α-diazoesters. The ester functionality at the bridgehead position would be a useful synthetic handle for further derivatization to complex molecules including natural products.

© 2019 American Chemical Society. We report a general protocol for the light-driven isomerization of cyclic aliphatic alcohols to linear carbonyl compounds. These reactions proceed via proton-coupled electron-transfer activation of alcohol O-H bonds followed by subsequent C-C β-scission of the resulting alkoxy radical intermediates. In many cases, these redox-neutral isomerizations proceed in opposition to a significant energetic gradient, yielding products that are less thermodynamically stable than the starting materials. A mechanism is presented to rationalize this out-of-equilibrium behavior that may serve as a model for the design of other contrathermodynamic transformations driven by excited-state redox events.

© 2018 American Chemical Society. Photoaffinity labeling (PAL) is an important tool in chemical biology research, but application of α-ketoamides for PAL has been hampered by their photoinstability. Here, we show that 2-thienyl-substituted α-ketoamide is a superior photoreactive group for PAL. Studies with a series of synthetic mannose-conjugated α-ketoamides revealed that 2-thienyl substitution of α-ketoamide decreased the electrophilicity of the keto group and reduced the rate of photodegradation. Mannose-conjugated thienyl α-ketoamide showed greater concanavalin A labeling efficiency than other alkyl or phenyl-substituted α-ketoamides. In comparison with representative conventional photoreactive groups, 2-thienyl ketoamide showed reduced labeling of nontarget proteins, probably owing to its lower hydrophobicity.

© 2017 Elsevier Ltd We describe a total synthesis of a polyunsaturated fatty acid (PUFA)-containing glucuronosyldiacylglycerol (GlcADG), which is a surrogate glycolipid whose synthesis is remarkably upregulated in plant membranes under phosphorus-depleted conditions. Glycosylation between the glucuronide donor bearing 3,4-dimethoxybenzyl (DMPM) protecting groups and di-acylglycerol acceptor proceeded smoothly in the presence of gold(I) catalyst to provide the protected α-isomer of GlcADG as the major product.

© Georg Thieme Verlag. We developed a photo-chemical coupling reaction of α-keto esters with several simple alcohols, alkanes, ethers, and amides. Use of tertiary alkyl ester, α-cumyl ester, is the key for avoiding the known photo-degradation process. Intermolecular C-H bond activation and subsequent C-C bond formation were promoted by irradiation with an LED lamp (365 nm) without any additives. Among the coupling partners, reactions with sterically less demanding amides proceeded efficiently to provide unique N-acyl-β-amino-α-hydroxy acid derivatives. In benzene or acetone as a solvent, the reaction with a solid amino acid derivative provided a precursor of tetrahydro-1,4-diazepine-2,5-dione derivatives.

© 2015 Elsevier Ltd. A novel type of photocyclization of α-ketoamides was developed, affording unique cyclopropanols bearing amide functionality. N-tert-Butyl, N-trityl, or N-non-substituted α-ketoamides with a bulky substituent at the β-position of the amide functionality were efficiently converted to corresponding cyclopropanols through the activation of the γ-C-H bond followed by C-C bond formation between the α- and γ-positions of the amide. Hydrogen abstraction from the γ-position of the amide was considered to be the rate-determining step of cyclopropanol formation, based on the kinetic isotope effect. Cyclopropanols could be converted to two different types of functionalized α-ketoamides depending on the method of ring-opening.

© 2015 FCCA (Forum: Carbohydrates Coming of Age). This mini-review focuses on the synthesis and biological activities of sialic acid (SA) derivatives with a C-glycosidic linkage in place of the standard O-glycosidic bond at the C-2 position. We summarize reported synthetic methodologies for monoand di-saccharides in separate sections. Then, we introduce our strategy for the construction of C-sialoside linkages utilizing Ireland-Claisen rearrangement reaction and its application to the synthesis of a ganglioside GM4 analogue. Although C-sialosides are expected to be useful as sialidase-resistant analogues of sialoglycoconjugates (sialoGCs), their biological activities have not yet been investigated in detail. Herein we briefly discuss the potential applications of C-sialosides.

Molecular probes based on 3-[(dodecylthiocarbonyl)methyl]glutarimide (DTCM-glutarimide) were synthesized and assessed for inhibitory activity against LPS-induced NO production. Among the probes examined, several derivatives exhibited potential for use in determining the target proteins of DTCM-glutarimide. © 2011 Elsevier Ltd. All rights reserved.

We previously reported that 9-methylstreptimidone, a piperidine compound isolated from a culture filtrate of Streptomyces, induces apoptosis selectively in adult T-cell leukemia cells. It was screened for a compound that inhibits LPS-induced NF-κB and NO production in mouse macrophages. However, 9-methystreptimidone is poorly obtained from the producing microorganism and difficult to synthesize. Therefore, in the present research, we studied the structure-activity relationship to look for new selective inhibitors. We found that the structure of the unsaturated hydrophobic portion of 9-methylstreptimidone was essential for the inhibition of LPS-induced NO production. Among the 9-methylstreptimidone-related compounds tested, (±)-4,α-diepi-streptovitacin A inhibited NO production in macrophage-like cells as potently as 9-methylstreptimidone and without cellular toxicity. Moreover, this compound selectively induced apoptosis in adult T-cell leukemia MT-1 cells. Copyright © 2012 Cognizant Comm. Corp. All rights reserved.