Development of a generic activation mode: nucleophilic α-substitution of ketones via oxy-allyl cations

Oxy-allyl cations have been known as transient electrophilic species since they were first proposed as intermediates in the Favorskii rearrangement in 1894. Since that time, they also have been used as a mode of activation for [4 + 3] cycloadditions in a variety of natural product syntheses. In this manuscript, we describe a method for the interception of oxy-allyl cations with a diverse range of common nucleophiles, thereby demonstrating the value of this intermediate as a generic mode of activation. This simple, mild, room temperature protocol allows for the formation of a variety of high value carbon–carbon and carbon–heteroatom bonds that are readily incorporated within a series of cyclic and acyclic ketone systems. Initial efforts into the development of an enantioselective catalytic variant are also described

Erratum: Development of a generic activation mode: nucleophilic a-substitution of ketones via oxy-allyl cations

Erratum.Oxy-allyl cations have been known as transient electrophilic species since they were first proposed as intermediates in the Favorskii rearrangement in 1894. Since that time, they also have been used as a mode of activation for [4 + 3] cycloadditions in a variety of natural product syntheses. In this manuscript, we describe a method for the interception of oxy-allyl cations with a diverse range of common nucleophiles, thereby demonstrating the value of this intermediate as a generic mode of activation. This simple, mild, room temperature protocol allows for the formation of a variety of high value carbon–carbon and carbon–heteroatom bonds that are readily incorporated within a series of cyclic and acyclic ketone systems. Initial efforts into the development of an enantioselective catalytic variant are also described

Development of a generic activation mode: nucleophilic a-substitution of ketones via oxy-allyl cations †

Oxy-allyl cations have been known as transient electrophilic species since they were first proposed as intermediates in the Favorskii rearrangement in 1894. Since that time, they also have been used as a mode of activation for [4 + 3] cycloadditions in a variety of natural product syntheses. In this manuscript, we describe a method for the interception of oxy-allyl cations with a diverse range of common nucleophiles, thereby demonstrating the value of this intermediate as a generic mode of activation. This simple, mild, room temperature protocol allows for the formation of a variety of high value carbon-carbon and carbonheteroatom bonds that are readily incorporated within a series of cyclic and acyclic ketone systems. Initial efforts into the development of an enantioselective catalytic variant are also described

Oxy-Allyl Cation Catalysis: An Enantioselective Electrophilic Activation Mode

A generic activation mode for asymmetric LUMO-lowering catalysis has been developed using the long-established principles of oxy-allyl cation chemistry. Here, the enantioselective conversion of racemic α-tosyloxy ketones to optically enriched α-indolic carbonyls has been accomplished using a new amino alcohol catalyst in the presence of electron-rich indole nucleophiles. Kinetic studies reveal that the rate-determining step in this S_N1 pathway is the catalyst-mediated α-tosyloxy ketone deprotonation step to form an enantiodiscriminant oxy-allyl cation prior to the stereodefining nucleophilic addition event

Oxy-Allyl Cation Catalysis: An Enantioselective Electrophilic Activation Mode

A generic activation mode for asymmetric LUMO-lowering catalysis has been developed using the long-established principles of oxy-allyl cation chemistry. Here, the enantioselective conversion of racemic α-tosyloxy ketones to optically enriched α-indolic carbonyls has been accomplished using a new amino alcohol catalyst in the presence of electron-rich indole nucleophiles. Kinetic studies reveal that the rate-determining step in this S_N1 pathway is the catalyst-mediated α-tosyloxy ketone deprotonation step to form an enantiodiscriminant oxy-allyl cation prior to the stereodefining nucleophilic addition event

In vivo bioluminescence imaging of labile iron accumulation in a murine model of Acinetobacter baumannii infection.

Iron is an essential metal for all organisms, yet disruption of its homeostasis, particularly in labile forms that can contribute to oxidative stress, is connected to diseases ranging from infection to cancer to neurodegeneration. Iron deficiency is also among the most common nutritional deficiencies worldwide. To advance studies of iron in healthy and disease states, we now report the synthesis and characterization of iron-caged luciferin-1 (ICL-1), a bioluminescent probe that enables longitudinal monitoring of labile iron pools (LIPs) in living animals. ICL-1 utilizes a bioinspired endoperoxide trigger to release d-aminoluciferin for selective reactivity-based detection of Fe2+ with metal and oxidation state specificity. The probe can detect physiological changes in labile Fe2+ levels in live cells and mice experiencing iron deficiency or overload. Application of ICL-1 in a model of systemic bacterial infection reveals increased iron accumulation in infected tissues that accompany transcriptional changes consistent with elevations in both iron acquisition and retention. The ability to assess iron status in living animals provides a powerful technology for studying the contributions of iron metabolism to physiology and pathology

The histone demethylase Phf2 acts as a molecular checkpoint to prevent NAFLD progression during obesity.

Aberrant histone methylation profile is reported to correlate with the development and progression of NAFLD during obesity. However, the identification of specific epigenetic modifiers involved in this process remains poorly understood. Here, we identify the histone demethylase Plant Homeodomain Finger 2 (Phf2) as a new transcriptional co-activator of the transcription factor Carbohydrate Responsive Element Binding Protein (ChREBP). By specifically erasing H3K9me2 methyl-marks on the promoter of ChREBP-regulated genes, Phf2 facilitates incorporation of metabolic precursors into mono-unsaturated fatty acids, leading to hepatosteatosis development in the absence of inflammation and insulin resistance. Moreover, the Phf2-mediated activation of the transcription factor NF-E2-related factor 2 (Nrf2) further reroutes glucose fluxes toward the pentose phosphate pathway and glutathione biosynthesis, protecting the liver from oxidative stress and fibrogenesis in response to diet-induced obesity. Overall, our findings establish a downstream epigenetic checkpoint, whereby Phf2, through facilitating H3K9me2 demethylation at specific gene promoters, protects liver from the pathogenesis progression of NAFLD

Copper regulates cyclic-AMP-dependent lipolysis.

Cell signaling relies extensively on dynamic pools of redox-inactive metal ions such as sodium, potassium, calcium and zinc, but their redox-active transition metal counterparts such as copper and iron have been studied primarily as static enzyme cofactors. Here we report that copper is an endogenous regulator of lipolysis, the breakdown of fat, which is an essential process in maintaining body weight and energy stores. Using a mouse model of genetic copper misregulation, in combination with pharmacological alterations in copper status and imaging studies in a 3T3-L1 white adipocyte model, we found that copper regulates lipolysis at the level of the second messenger, cyclic AMP (cAMP), by altering the activity of the cAMP-degrading phosphodiesterase PDE3B. Biochemical studies of the copper-PDE3B interaction establish copper-dependent inhibition of enzyme activity and identify a key conserved cysteine residue in a PDE3-specific loop that is essential for the observed copper-dependent lipolytic phenotype

Copper regulates cyclic-AMP-dependent lipolysis.

Cell signaling relies extensively on dynamic pools of redox-inactive metal ions such as sodium, potassium, calcium and zinc, but their redox-active transition metal counterparts such as copper and iron have been studied primarily as static enzyme cofactors. Here we report that copper is an endogenous regulator of lipolysis, the breakdown of fat, which is an essential process in maintaining body weight and energy stores. Using a mouse model of genetic copper misregulation, in combination with pharmacological alterations in copper status and imaging studies in a 3T3-L1 white adipocyte model, we found that copper regulates lipolysis at the level of the second messenger, cyclic AMP (cAMP), by altering the activity of the cAMP-degrading phosphodiesterase PDE3B. Biochemical studies of the copper-PDE3B interaction establish copper-dependent inhibition of enzyme activity and identify a key conserved cysteine residue in a PDE3-specific loop that is essential for the observed copper-dependent lipolytic phenotype