Maria J. Alves

GENERATION AND DIELS-ALDER REACTIONS OF T-BUTYL 2H-AZIRINE-3-CARBOXYLATE

Abstract The azirinyl ester 2 (R = Bu t ) has been generated by thermolysis of t-butyl 2-azidoacrylate. It is too unstable to allow its full characterisation but it has been intercepted by Diels-Alder cycloaddition to several dienes. Addition to a chiral diene 8 is highly diastereoselective.

Novel aziridine esters by the addition of aromatic nitrogen heterocycles to a 2H-azirine-3-carboxylic ester

Abstract Methyl 2-(2,6-dichlorophenyl)-2 H -azirine-3-carboxylate acts as an efficient alkylating agent for a variety of five-membered aromatic heterocycles. The aziridines derived from heterocycles that bear an α-carbonyl substituent react with TFA to give pyrroloimidazoles; 2,6-dichlorobenzaldehyde is also produced.

Novel pyridine-2,4,6-tricarbohydrazide derivatives: Design, synthesis, characterization and in vitro biological evaluation as α- and β-glucosidase inhibitors

A range of novel pyridine 2,4,6-tricarbohydrazide derivatives (4a-4h) were synthesized and its biological inhibition towards α- and β-glucosidases was studied. Most of the compounds demonstrate to be active against α-glucosidase, and quite inactive/completely inactive against β-glucosidase. A number of compounds were found to be more active against α-glucosidase than the reference compound acarbose (IC50 38.25±0.12μM); being compound 4d with the p-hydroxy phenyl motive the most active (IC50 20.24±0.72μM). Molecular modeling studies show the interactions of compound 4d with the active site of target α-glucosidase kinase.

Synthesis and evaluation of α-, β-glucosidase inhibition of 1-N-carboxamide-1-azafagomines and 5-epi-1-azafagomines

1-N-Carboxamide 1-azafagomines and 5-epi-1-azafagomines were obtained from 1-azafagomine and 5-epi-1-azafagomine. The hydroxyl groups and the N-2 pyridazine position were protected prior to reaction with different isocyanates to form ureas. Protective groups were removed leading to the target compounds in 18-23% global yields. Final compounds were tested towards α- and β-glucosidases.

Molecular docking and glucosidase inhibition studies of novel N-arylthiazole-2-amines and Ethyl 2-[aryl(thiazol-2-yl)amino]acetates

This study describes an efficient synthesis of a series of novel ethyl 2-[aryl(thiazol-2-yl)amino]acetates (4a–l) from N-arylthiazole-2-amines (3a–l). The reaction conditions were optimized and the best results were obtained when ethyl chloroacetate was used as alkylating agent and NaH as base in THF. α-glucosidase and β-glucosidase inhibition activities of N-arylthiazole-2-amines (3a–l) and ethyl 2-[aryl(thiazol-2-yl)amino]acetates (4a–l) were determined, which revealed that most of the compounds showed high percentage inhibition towards the enzymes. Among the synthesized compounds, 4e appeared to have the highest inhibition towards α-glucosidase having IC50 value of 150.4 ± 1.9 μM which was almost two folds as compared to acarbose (336.9 ± 9.0 μM) taken as standard. Molecular docking of the compounds 3g, 3f, 4a, and 4e was also performed which showed their bonding modes to the enzyme’s active sites via amino and acetate groups, respectively.

Total Facial Discrimination of 1,3-Dipolar Cycloadditions in a d-Erythrose 1,3-Dioxane Template: Computational Studies of a Concerted Mechanism

A new d-erythrose 1,3-dioxane derivative was synthesized from d-glucose and found to be a highly stereoselective template as a dipolarophile. Different 1,3-dipoles of allenyl-type were employed, giving different regioselectivities, depending on its nature; the regioselectivity is complete with alkyl azides and phenyldiazomethane, but is inexistence with nitrile oxides. Computational studies were performed to understand the mechanisms of cycloadditions. All the studied cycloadditions were found to be concerted involving small free activation energies and are all exoenergonic. The stereoselectivity is due to a combined result of the steric effect H-8a and the hyperconjugative effect of the *C-O to the incoming 1,3-dipole. The regioselectivity observed in alkyl azides and phenyldiazomethane is mostly dependent on the distortion effect during the cycloaddition process. This distortion effect is however higher in the alkyl azide compounds than in phenyldiazomethane.

STUDY BASED ON ELECTRONIC DESCRIPTORS OF THE DIASTEREOSELECTIVE AZA-DIELS-ALDER CYCLOADDITION OF [(1R)-10-(N,N-DIETHYLSULFAMOYL)ISOBORNYL] 2H-AZIRINE-3-CARBOXYLATE TO E,E-1,4-DIACETOXY-1,3-BUTADIENE

ABSTRACT Cycloaddition of chiral [(1 R )-10-( N , N -diethylsulfamoyl)isobornyl] 2 H -azirine-3-carboxylate to E , E -1,4-diacetoxy-1,3-butadiene shows complete diatereoselectivity giving a single cycloadduct (-)-(2 S ,5 R ,6 R )-6-[(1 R )-10-( N , N -diethylsulfamoyl)isobornyloxycarbonyl]-1-azabicyclo[4.1.0]hept-3-ene-2,5-diyldiacetate. Our main objective is to identify electronic/steric parameters capable of describing the observed tendencies of this reaction. The results of the calculations conclude that: even though the steric factors can play an important role at the initial steps of the reaction, at the transition states the behavior of several electronic parameters; like hardness, polarizability, aromaticity, charge transfer, etc is decisive enough to justify the obtained product. Finally, this work summarizes an exhaustive analysis of electronic descriptors and empirical reactivity principles, reaching a definitive and comprehensive explanation to the observed experimental result.

Total Stereoselective Michael Addition of N- and S- Nucleophiles to a d-Erythrosyl 1,5-Lactone Derivative. Experimental and Theoretical Studies Devoted to the Synthesis of 2,6-Dideoxy-4-functionalized-d-ribono-hexono-1,4-lactone

The synthesis of a 1,5-lactone 2,4- O-alkylidene-d-erythrose derivative was found to be a highly stereoselective template in Michael addition trough the reaction of a d-erythrosyl 1,5-lactone derivative with nitrogen and sulfur nucleophiles. The sulfur adducts formed are 1 (d-erythrose derivative):1 (nucleophile), and the nitrogen adducts are 1:2. Both were then treated under HCl to give 2,6-dideoxy-4-functionalized-d- ribono-hexono-1,4-lactone by a reaction cascade in high overall yield. Reactions scale up even improves the yield. The theoretical and computational results clearly explain the origin of the stereoselectivity, and the energetic course of reactions starting with nitrogen and sulfide nucleophiles. Considering that the 1,4-lactones obtained in this work offer a new molecular scaffold for organic synthesis, these new results provide a solid theoretical platform that can be used to speed up synthesis of other derivatives in a stereo- and regioselective way.