RESUMO
The pharmaceutical industry is increasingly faced with challenging separations of complex crude reaction mixtures at the microscale that require the adoption of new platforms for rapid target isolation, impurity determination, and quantitation. In this study, we describe an online microscale one- or two-dimensional liquid chromatography (1D/2D-LC) system with heart-cutting and multi (triple) detector triggering in either dimension to address this need. The advantages of charged aerosol detection (CAD) are discussed for the direct quantitation of limited quantity samples, without utilizing a second analytical instrument or gradient compensation pump. In addition to the significant time and cost savings, there is no minimum recovery requirement that exists when compared to gravimetric methods for accurate microscale quantitation. This platform has been successfully used to purify 0.5-5.0 mg scale reactions in 96- or 384-well reaction plates with a gradient time of 4 min per sample. Separations performed in both dimensions are complete in less than 12 min, including trapping and column equilibration time. The isolated arrays of small-quantity investigational compounds at a high purity enable rapid exploration of chemical reaction parameters and synthetic route scouting for biological target validation.
Assuntos
Cromatografia Líquida de Alta Pressão , Aerossóis/química , Cromatografia Líquida de Alta Pressão/métodosRESUMO
Seven-membered-ring trans-alkenes undergo rapid, uncatalyzed carboboration reactions to form trialkylboranes as single diastereomers. In contrast with other trialkylboranes, which can ignite in the presence of oxygen, these trialkylboranes are stable in air. Hindered trialkylboranes can undergo reverse hydroboration reactions to form allylic silanes or can be oxidized to afford highly substituted triols. This reaction sequence permits the construction of compounds with up to five consecutive stereocenters. Control experiments and computational studies support a concerted mechanism for the migratory insertion of the alkene into the carbon-boron bond, similar to the mechanism for hydroboration.
Assuntos
Alcenos/química , Boranos/química , Ar , Alquilação , Catálise , Estrutura MolecularRESUMO
trans-Oxasilacycloheptenes are highly reactive strained alkenes. Competition reactions showed that these seven-membered ring trans-alkenes underwent [4+2] cycloaddition reactions faster than a trans-cyclooctene. They also reacted with quinones and dimethyl acetylenedicarboxylate to form adducts with high diastereoselectivity. Kinetic studies showed that ring strain increases nucleophilicity by approximately 10(9).
RESUMO
The hydrolysis of 4-alkoxy-substituted acetals was accelerated by about 20-fold compared to that of sterically comparable substrates that do not have an alkoxy group. Rate accelerations are largest when the two functional groups are linked by a flexible cyclic tether. When controlled for the inductive destabilization, an alkoxy group can accelerate acetal hydrolysis by up to 200-fold. The difference in rates of acetal hydrolysis between a substrate where the alkoxy group was tethered to the acetal group by a five-membered ring compared to one where it was tethered by an eight-membered ring was less than 100-fold, suggesting that fused-ring intermediates were not formed. By comparison, the difference in rates of solvolysis of structurally related tosylates were nearly 10(6)-fold between the five- and eight-membered ring series. This observation implicates neighboring-group participation in the solvolysis of tosylates but not in the hydrolysis of acetals. The acceleration of acetal hydrolysis by an alkoxy group is better explained by electrostatic stabilization of intermediates that accumulate positive charge at the acetal carbon atom.
Assuntos
Acetais/química , Álcoois/química , Compostos Bicíclicos Heterocíclicos com Pontes/síntese química , Oniocompostos/síntese química , Compostos de Tosil/química , Compostos Bicíclicos Heterocíclicos com Pontes/química , Hidrólise , Íons/síntese química , Íons/química , Estrutura Molecular , Oniocompostos/química , Solubilidade , Eletricidade EstáticaRESUMO
Nucleophilic substitution reactions of acetals having benzyloxy groups four carbon atoms away can be highly diastereoselective. The selectivity in several cases increased as the reactivity of the nucleophile increased, in violation of the reactivity/selectivity principle. The increase in selectivity with reactivity suggests that multiple conformational isomers of reactive intermediates can give rise to the products.
Assuntos
Acetais/química , Álcoois/química , Compostos Alílicos/química , Acetais/síntese química , Álcoois/síntese química , Compostos Alílicos/síntese química , Cinética , EstereoisomerismoRESUMO
In contrast to observations with carbohydrates, experiments with 4-alkoxy-substituted acetals indicate that an alkoxy group can accelerate acetal hydrolysis by up to 20-fold compared to substrates without an alkoxy group. The acceleration of ionization in more flexible acetals can be up to 200-fold when compensated for inductive effects.
Assuntos
Acetais/química , Ânions/química , Eletricidade Estática , HidróliseRESUMO
Toll-like receptors 7 and 8 are involved in modulating the adaptive and innate immune responses, and their activation has shown promise as a therapeutic strategy in the field of immuno-oncology. While systemic exposure to TLR7/8 agonists can result in poor tolerance, combination therapies and targeted delivery through antibody-drug conjugates (ADCs) can help mitigate adverse effects. Described herein is the identification of a novel and potent series of pyrazolopyrimidine-based TLR7/8 agonists with tunable receptor selectivity. Representative agonists from this series were successfully able to induce the production of various proinflammatory cytokines and chemokines from human peripheral blood mononuclear cells. Anti-HER2-25 and anti-HER2-26 ADCs made from this class of payloads demonstrated mechanism-based activation of TLR7/8 in a THP1/N87 coculture system.
Assuntos
Desenho de Fármacos , Imunoconjugados , Receptor 7 Toll-Like , Receptor 8 Toll-Like , Humanos , Receptor 7 Toll-Like/agonistas , Receptor 8 Toll-Like/agonistas , Receptor 8 Toll-Like/metabolismo , Imunoconjugados/farmacologia , Imunoconjugados/química , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/metabolismo , Leucócitos Mononucleares/imunologia , Relação Estrutura-Atividade , Pirimidinas/farmacologia , Pirimidinas/química , Pirimidinas/síntese química , Citocinas/metabolismo , Receptor ErbB-2/metabolismo , Receptor ErbB-2/antagonistas & inibidores , Pirazóis/farmacologia , Pirazóis/químicaRESUMO
Seven-membered-ring trans-alkenes undergo rapid hydro- and carboalumination reactions in the absence of a catalyst with complete regio- and diastereoselectivity. Control experiments, including deuterium labeling, adding radical inhibitors, and using a radical clock, suggest that these reactions proceed by a concerted mechanism. The products of the reaction possess a new carbon-aluminum bond that can then undergo subsequent transformations, particularly oxidation, providing functionalized products as single stereoisomers.