Enantioenriched trisubstituted lactones were obtained in good yields and moderate to very good enantioselectivities in one-pot process, which implies a sequential organocatalyzed Michael addition of ketones to enals, followed by catalytic intramolecular diastereoselective Tishchenko reaction and lactonization. The final lactones were obtained as single diastereoisomers, demonstrating that the mixture of the anti and syn diastereomers epimerized to the syn hydroxy ester during the oxido-reduction step.
Background: Dopamine (DA) is an important neurotransmitter with a fundamental role in regulatory functions related to the central, peripheral, renal, and hormonal nervous systems. Dopaminergic neurotransmission dysfunctions are commonly associated with several diseases; thus, in situ quantification of DA is a major challenge. To achieve this goal, enzyme-based biosensors have been employed for substrate recognition in the past. However, owing to their sensitivity to changes in temperature and pH levels. Results: New peptide bioreceptors have been developed. Based on this, 45 in silico bioreceptors were designed to exhibit a higher affinity than that of the DA transporters (DATs). The design was based on the active sites of crystallized enzyme structures that are physiologically related to DA. These affinities were calculated using AutoDock Vina and by assessing the interaction energy between DA and the active DAT site. The controlled variables in the design were amino acids, bond type, steric volume, stereochemistry, affinity, and interaction distances. Conclusions: Three bioreceptor candidates presenting promising values in terms of DA affinity and distance were obtained.
α,β‐Unsaturated aldehydes with aliphatic, electron‐poor aromatic, or electron‐withdrawing substituents at the β position easily react with different ketones leading to enantioenriched hemiacetals, which were further oxidized to give 4,5,6‐trisubstituted‐3,4‐dihydropyranones in good yields and with excellent enantioselectivities. The behavior of the ketones is dependent on the α substituent of the carbonyl group, and a fine‐tuning of the pKa values is necessary to obtain good results.
Abstract.The reaction of enals with ´-diaryl-substituted acetones (pKa > 18) catalyzed by (S)-1-(2-pyrrolidinylmethyl) pyrrolidine provides a direct access to enantioenriched 2,5,6-trisubstituted-3-hydroxy cyclohexanones. The process constitutes a highly stereoselective organocatalytic tandem Michael-intramolecular aldol reaction. It has been demonstrated that the stereoselection is dependent on the reaction conditions because only syn diastereoisomers are able to cyclize, and that anti diastereoisomers participate in a retro-Michael process decreasing the enantioselection.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.