Background: Immune checkpoint inhibitors (ICIs) have significantly improved outcomes in various cancers. ICI treatment is associated with the incidence of immune-related adverse events (irAEs) which can affect any organ. Data on irAEs occurrence in relation to sex- differentiation and their association with gender-specific factors are limited.
View Article and Find Full Text PDFThe current work explores the sodium hydride mediated polycondensation of aliphatic diols with diethyl carbonate to produce both aliphatic polycarbonates and cyclic carbonate monomers. The lengths of the diol dictate the outcome of the reaction; for ethylene glycol and seven other 1,3-diols with a wide array of substitution patterns, the corresponding 5-membered and 6-membered cyclic carbonates were synthesized in excellent yield (70-90%) on a 100 gram scale. Diols with longer alkyl chains, under the same conditions, yielded polycarbonates with an ranging from 5000 to 16 000.
View Article and Find Full Text PDFA highly efficient aldehyde-olefin metathesis catalysed by the carbocation, 4-phenylphenyl-diphenylmethylium ion, has been developed. This protocol is characterized by high yields, low catalyst loading (down to 2 mol%), good functional group compatibility and mild reaction conditions.
View Article and Find Full Text PDFAn array of branched poly(ɛ-caprolactone)s was successfully synthesized using an one-pot inimer promoted ring-opening multibranching copolymerization (ROCP) reaction. The biorenewable, commercially available yet unexploited comonomer and initiator 2-hydroxy-γ-butyrolactone was chosen as the inimer to extend the use of 5-membered lactones to branched structures and simultaneously avoiding the typical tedious work involved in the inimer preparation. Reactions were carried out both in bulk and in solution using stannous octoate (Sn(Oct)) as the catalyst.
View Article and Find Full Text PDFIn general, Lewis acid catalysts are metal-based compounds that owe their reactivity to a low-lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions.
View Article and Find Full Text PDFHere we present a general and common catalytic asymmetric strategy for the total and formal synthesis of a broad number of optically active natural products from the corynantheine and ipecac alkaloid families, for example, indolo[2,3-a]- and benzo[a]quinolizidines. Construction of the core alkaloid skeletons with the correct absolute and relative stereochemistry relies on an enantioselective and diastereodivergent one-pot cascade sequence followed by an additional diastereodivergent reaction step. This allows for enantio- and diastereoselective synthesis of three out of four possible epimers of the quinolizidine alkaloids that begin from common and easily accessible starting materials by using a common synthetic route.
View Article and Find Full Text PDFA screening of non-conventional yeast species and several Saccharomyces cerevisiae (baker's yeast) strains overexpressing known carbonyl reductases revealed the S. cerevisiae reductase encoded by YMR226c as highly efficient for the reduction of the diketones 1 and 2 to their corresponding hydroxyketones 3-6 (Scheme 1) in excellent enantiomeric excesses. Bioreduction of 1 using the genetically engineered yeast TMB4100, overexpressing YMR226c, resulted in >99% ee for hydroxyketone (+)-4 and 84-98% ee for (-)-3, depending on the degree of conversion.
View Article and Find Full Text PDFA mild, thermal Alder-ene reaction of enallenes has been developed. The allenic double bond acts as the "ene" and generates a carbon-carbon bond to an unactivated olefinic "enophile" in DMF at 120 degrees C to give [n.3.
View Article and Find Full Text PDFThe development of a general organocatalyst for the alpha-functionalization of aldehydes, via an enamine intermediate, is presented. Based on optically active alpha,alpha-diarylprolinol silyl ethers, the scope and applications of this catalyst for the stereogenic formation of C-C, C-N, C-F, C-Br, and C-S bonds are outlined. The reactions all proceed in good to high yields and with excellent enantioselectivities.
View Article and Find Full Text PDFAn organocatalytic asymmetric multicomponent domino and a conjugated addition reaction to alpha,beta-unsaturated aldehydes are presented. The development is based, first, on an organocatalyzed highly enantioselective nucleophilic thiol addition to the beta-carbon atom in the iminium ion intermediate, followed by an electrophilic amination of the alpha-carbon atom to the enamine intermediate. The multicomponent reactions proceed to give enantiopure amino-thiols in moderate to good yields.
View Article and Find Full Text PDFA novel palladium(0)-catalyzed cycloisomerization of enallenes has been developed. This reaction, catalyzed by [Pd(dba)2] (dba=dibenzylideneacetone) in acetic acid, results in the formation of cyclopentene derivatives and [n.3.
View Article and Find Full Text PDFThe first asymmetric organocatalytic epoxidation of alpha,beta-unsaturated aldehydes is presented. A chiral bisaryl-silyl-protected pyrrolidine acts as a very selective epoxidation organocatalyst using simple oxidation agents, such as hydrogen peroxide and tert-butyl hydroperoxide. The asymmetric epoxidation reactions proceed under environmental friendly reaction condition in, for example, water mixtures of alcohols, and the scope of the reaction is demonstrated by the formation of optically active alpha,beta-epoxy aldehydes in high yields and enantioselectivities >94% ee.
View Article and Find Full Text PDFPalladium(0)-catalyzed reaction of allene-substituted allylic carboxylates 3-8 employing 2-5 mol % of Pd(dba)(2) in refluxing toluene leads to the carbocyclization and elimination of carboxylic acid to give bicyclo[4.3.0]nonadiene and bicyclo[5.
View Article and Find Full Text PDFReaction of allene-substituted cyclohexa- and cyclohepta-1,3-dienes with [PdCl(2)(PhCN)(2)] gave eta(3)-(1,2,3)-cyclohexenyl- and eta(3)-(1,2,3)-cycloheptenylpalladium complexes, respectively, in which C-C bond formation between the allene and the 1,3-diene has occurred. Analysis of the (pi-allyl)palladium complexes by NMR spectroscopy, using reporter ligands, shows that the C-C bond formation has occurred by a trans carbopalladation involving nucleophilic attack by the middle carbon atom of the allene on a (pi-diene)palladium(II) complex. The stereochemistry of the (pi-allyl)palladium complexes was confirmed by benzoquinone-induced stereoselective transformations to allylic acetates.
View Article and Find Full Text PDFA new efficient palladium(II)-catalyzed oxidative carbocyclization has been developed. It was found that allene-substituted olefins 1 cyclized in the presence of 1 mol % Pd(O2CCF3)2 and p-benzoquinone (2 equiv) to give bicyclic ring systems 2 in good to excellent yields. The cyclization constitutes a new type of carbon-carbon bond forming reaction between an allene and an olefin under oxidative conditions.
View Article and Find Full Text PDFIn the palladium-catalyzed cyclization of allenic allylic esters using Pd(dba)2 as catalyst, it was shown that the allene acts as a carbon nucleophile. Intermediates were isolated and stereochemical studies established that the double bond of the allene has attacked the (pi-allyl)palladium intermediate on the face opposite to that of palladium.
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