Joined together, organocatalysts aldehydes and sulfones: A diaryl prolinol silyl ether was found to catalyse efficiently and enantioselectively the conjugate addition of aldehydes to vinyl sulfones (see scheme). The ample synthetic utility of the resulting adducts is illustrated.
Prolyl oligopeptidase (POP) is a cytosolic serine peptidase that hydrolyzes proline-containing peptides at the carboxy terminus of proline residues. This peptidase has gained importance as a target for the treatment of cognitive disturbances of patients with neuropsychiatric diseases. Our research addresses the identification of POP inhibitors from a small focused library of polar heterocyclic compounds arising from multicomponent reactions. Two selective POP-specific inhibitors were identified on the basis of their inhibition of dipeptidyl peptidase IV. The most active compounds were evaluated for their in vitro transport through the blood-brain barrier (BBB) using a parallel artificial membrane permeability assay. Our results show for the first time that benzimidazolium salts are new POP-inhibitory scaffolds with properties of solubility, specificity, and lipophilicity that may allow them to cross the BBB by passive diffusion. These findings constitute an excellent starting point to synthesize new POP inhibitors with enhanced properties.
The natural tendency of 1,4-dihydropyridines to undergo ªbiomimeticº oxidation to afford pyridinium salts can be switched off and, through the use of reagents that interact electrophilically with the enamine moiety present in the heterocyclic system, it is possible to promote alternative oxidations. In this way, efficient regio-and stereocontrolled synthetic methods have been developed that lead to diversely substituted di-and tetrahydropyridines. These include iodoazida-
Michael addition of ethyl nitroacetate on α,β-unsaturated ketones followed by Nef oxidation under hydrolytic conditions yields γ-oxoacids instead of the corresponding α,δ-dioxoesters. A concerted decarboxylation step is proposed on the basis of computational results. Finally, conversion of the γ-ketoacids thus prepared into 1H-pyrrol-2(5H)-ones by reaction with primary amines under Paal-Knorr conditions is also reported.
Heterocyclic nitrogen compounds, including fused 1,5-naphthyridines, have versatile applications in the fields of synthetic organic chemistry and play an important role in the field of medicinal chemistry, as many of them have a wide range of biological activities. In this review, a wide range of synthetic protocols for the construction of this scaffold are presented. For example, Friedländer, Skraup, Semmlere-Wolff, and hetero-Diels-Alder, among others, are well known classical synthetic protocols used for the construction of the main 1,5-naphthyridine scaffold. These syntheses are classified according to the nature of the cycle fused to the 1,5-naphthyridine ring: carbocycles, nitrogen heterocycles, oxygen heterocycles, and sulphur heterocycles. In addition, taking into account the aforementioned versatility of these heterocycles, their reactivity is presented as well as their use as a ligand for metal complexes formation. Finally, those fused 1,5-naphthyridines that present biological activity and optical applications, among others, are indicated.
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