Carmen Escolano

Synthesis of 2-azabicyclo[3.3.1]nonanes by means of (carbamoyl)dichloromethyl radical cyclization

Abstract A new procedure for the synthesis of 2-azabicyclo[3.3.1]nonanes by intramolecular carboradical cyclization of 4-(trichloroacetamido)cyclohexenes substituted with an electron withdrawing substituent (ester or nitrile) is described. The procedure allows the preparation of synthetically interesting azabicyclos 14 and 15 in nearly 70% yield.

Enantioselective Formal Synthesis of (+)-Dihydrocorynantheine and (-)-Dihydrocorynantheol †

The enantioselective construction of the 3-ethylindolo[2,3-a]quinolizidine moiety present in numerous indole alkaloids is reported, the key steps being a stereoselective cyclocondensation of (S)-tryptophanol with an appropriate racemic delta-oxoester and a regio- and stereoselective cyclization of the resulting oxazolopiperidones on the lactam carbonyl group. A new procedure for the removal of the hydroxymethyl auxiliary group, involving oxidation to an aldehyde, dehydration of the corresponding oxime, and reductive decyanation of the resulting alpha-aminonitrile, has been developed. The preparation of indoloquinolizidine 27 represents a formal total synthesis of (+)-dihydrocorynantheine, (-)-dihydrocorynantheol, and other indolo[2,3-a]quinolizidine and oxindole alkaloids bearing the same substitution pattern.

Triheptanoin Supplementation to Ketogenic Diet Curbs Cognitive Impairment in APP/PS1 Mice Used as a Model of Familial Alzheimer’s Disease

Diets containing a high proportion of fat with respect to protein plus carbohydrates are capable of inducing ketone body production in the liver, which provides an energetic alternative to glucose. Some ketogenic diets have been tested as therapeutic strategies for treating metabolic disorders related to a deficiency in glucose-driven ATP generation. However, ketone bodies are not capable of providing extra tricarboxylic acid cycle intermediates, limiting the anabolic capacity of the cell. Therefore, it is reasonable to hypothesize that supplementing a ketogenic diet with anaplerotic compounds such as triheptanoin may improve ketogenic diet effectiveness. The present study tests this hypothesis in APP/PS1 (APPswe/PS1dE9) transgenic mice, used as a model of familial Alzheimers disease because impaired energy supply to neurons has been linked to this neurodegenerative process. Triheptanoin supplementation to a ketogenic diet for three months and starting at the age of three months reduces the memory impairment of APP/PS1 mice at the age of 6 months. The Aβ production and deposition were not significantly altered by the ketogenic diet, supplemented or not by triheptanoin. However, mice fed with triheptanoin-rich ketogenic diet have shown decreased astroglial response in the vicinity of Aβ plaques and decreased expression of the pro-inflammatory cytokine interferon-γ in astrocytes. These findings correlate with transcriptional up-regulation of the ROS detoxifying mechanisms Sirt1 and Pparg, thus linking triheptanoin with improved mitochondrial status. Present findings support the concept that ketogenic diets supplemented with anaplerotic compounds can be considered potential therapeutic strategies at early stages of Alzheimers disease.

Stereoselective α-amidoalkylation reactions of phenylglycinol-derived bicyclic lactams

The stereochemical outcome of α-amidoalkylation reactions from the chiral non-racemic bicyclic lactams trans-1 and cis-1 using indole, allyltrimethylsilane, higher order organocuprates, TMSCN, and Grignard reagents is discussed.

First asymmetric cascade reaction catalysed by chiral primary aminoalcohols.

Readily available chiral primary 1,2-aminoalcohols and diamines have been explored as organocatalysts for a domino Michael-aldol reaction. Their application in this organocascade process afforded cyclohexanone A with high levels of reactivity (up to 91% yield) and stereoselectivity (>97 : 3 d.r., up to 93% ee). Depending on the acid cocatalyst different chiral species (cyclic secondary amines vs. acyclic primary amines) might catalyse the process. In order to shed light on the catalytic activation, several experiments were carried out and a detailed possible reaction mechanism is proposed. Theoretical studies support the stereochemical outcome of the process.

Synthesis of enantiopure 2-azabicyclo[3.3.1]nonanes by a radical ring closure

Abstract The first synthesis of enantiomerically pure 2-azabicyclo[3.3.1]nonanes by an intramolecular radical reaction of the trichloroacetamido group bearing an ( S )- N -1-phenylethyl substituent with the silyl enol ether moiety in compounds 7 is described. The procedure allows the two enantiomers of the 2-azabicyclo[3.3.1]nonane-3,6-dione, 3 and ent - 3 , to be prepared separately. β-Lactam 8 and normorphan 9 are also formed from 7 through an initial radical translocation process in the cyclization step.

On the configuration of (3R, 8aS)-5-oxo-3-phenyl-2,3,6,7,8,8a-hexahydro-5H-oxazolo[3,2-a]pyridine

Abstract The configuration of (3R,8aS)-5-oxo-3-phenyl-2,3,6,7,8,8a-hexahydro-5H-oxazolo[3,2-a]pyridine 2 has been unambiguously confirmed by X-ray crystallographic analysis. A 1H NMR-based method for the stereochemical assignment of 3,8a-cis and trans phenylglycinol-derived bicyclic lactams is also proposed.

Cyclization of 1-(carbamoyl)dichloromethyl radicals upon activated alkenes. A new entry to 2-azabicyclo[3.3.1]nonanes

Abstract The synthesis of 2-azabicyclo[3.3.1]nonanes using a radical cyclization process as the piperidine ring-forming step is described. The reaction involves 1-(carbamoyl)-dichloromethyl radicals which react intramolecularly with simple or activated alkenes, such as enol acetates or silyl enol ethers.

Heme-Regulated eIF2α Kinase Modulates Hepatic FGF21 and Is Activated by PPARβ/δ Deficiency

Fibroblast growth factor 21 (FGF21), a peptide hormone with pleiotropic effects on carbohydrate and lipid metabolism, is considered a target for the treatment of diabetes. We investigated the role of peroxisome proliferator–activated receptor (PPAR) β/δ deficiency in hepatic FGF21 regulation. Increased Fgf21 expression was observed in the livers of PPARβ/δ-null mice and in mouse primary hepatocytes when this receptor was knocked down by small interfering RNA (siRNA). Increased Fgf21 was associated with enhanced protein levels in the heme-regulated eukaryotic translation initiation factor 2α (eIF2α) kinase (HRI). This increase caused enhanced levels of phosphorylated eIF2α and activating transcription factor (ATF) 4, which is essential for Fgf21-induced expression. siRNA analysis demonstrated that HRI regulates Fgf21 expression in primary hepatocytes. Enhanced Fgf21 expression attenuated tunicamycin-induced endoplasmic reticulum stress, as demonstrated by using a neutralizing antibody against FGF21. Of note, increased Fgf21 expression in mice fed a high-fat diet or hepatocytes exposed to palmitate was accompanied by reduced PPARβ/δ and activation of the HRI-eIF2α-ATF4 pathway. Moreover, pharmacological activation of HRI increased Fgf21 expression and reduced lipid-induced hepatic steatosis and glucose intolerance, but these effects were not observed in Fgf21-null mice. Overall, these findings suggest that HRI is a potential target for regulating hepatic FGF21 levels.

Structure-Directed Reversion in the π-Facial Stereoselective Alkylation of Chiral Bicyclic Lactams

The reversal of the pi-facial diastereoselectivity observed in the benzyl bromide alkylation of the enolate of phenylglycinol-derived oxazolopiperidone is examined by means of theoretical calculations and experimental assays. When the angular carbon adopts an R configuration, the endo addition is intrinsically favored due to the lower torsional strain induced in the TS, but for the reaction with benzyl bromide, which affords the exo product. This reversal is attributed to the formation of a C-H...pi hydrogen bond between the C-H unit of the C8a angular position and the benzene ring of the alkylating reagent. A similar secondary interaction explains the stereochemical reversion observed in the benzyl alkylation of the enolate of oxazolopyrrolidinone. These findings point out that the delicate balance between factors that dictate the diastereoselectivity in the alkylation of chiral byciclic lactams can be unexpectedly altered by weak secondary interactions. The results presented here provide valuable guidelines to tune the selective preparation of enantiopure bioorganic and pharmaceutical compounds.