Angelina M. de Almeida

Comparative Properties of Amazonian Oils Obtained by Different Extraction Methods

Pequi (Caryocar brasiliense Camb.), babaçu (Orbignya phalerata Mart.), buriti (Mauritia flexuosa), and passion fruit (Passiflora edulis) oils were studied to determine their antibacterial, antioxidant and cytotoxic activities, as well as their total phenol and carotenoid contents. The fatty acid contents were determined by GC-MS. The three types of passion fruit oils studied were refined, cold pressed or extracted from seeds in a Soxhlet apparatus. The oils thus obtained showed differences in antioxidant activity and carotenoid content, but were similar in regard to total phenols. Buriti and pequi had the highest carotenoid contents, while refined and cold pressed passion fruit oil displayed the highest antioxidant activity. Pequi oil was the only oil to display antibacterial and cytotoxic activity.

Synthesis of Acyl Carbamates via Four Component Pd-Catalyzed Carbonylative Coupling of Aryl Halides, Potassium Cyanate, and Alcohols

A simple and mild method is demonstrated for assembling acyl carbamates through a base-free four-component Pd-catalyzed carbonylation of aryl halides in the presence of potassium cyanate and alcohols in a two-chamber system. This approach produces a wide range of aryl acyl carbamates in good to excellent yields from the corresponding aryl bromides or iodides with near-stoichiometric carbon monoxide. In addition, the method can be extended to the synthesis of primary amides thereby expanding the usefulness of cyanate as an ammonia equivalent.

General method for the preparation of active esters by palladium-catalyzed alkoxycarbonylation of aryl bromides.

A useful method was developed for the synthesis of active esters by palladium-catalyzed alkoxycarbonylation of (hetero)aromatic bromides. The protocol was general for a range of oxygen nucleophiles including N-hydroxysuccinimide (NHS), pentafluorophenol (PFP), hexafluoroisopropyl alcohol (HFP), 4-nitrophenol, and N-hydroxyphthalimide. A high functional group tolerance was displayed, and several active esters were prepared with good to excellent isolated yields. The protocol was extended to access an important synthetic precursor to the HIV-protease inhibitor, saquinavir, by formation of an NHS ester followed by acyl substitution.

Synthesis and Antibacterial Activity of Aromatic and Heteroaromatic Amino Alcohols

Two series of aromatic and heteroaromatic amino alcohols were synthesized from alcohols and aldehydes and evaluated for their antibacterial activities. All the octylated compounds displayed a better activity against the four bacteria tested when evaluated by the agar diffusion method and were selected for the evaluation of minimal inhibitory concentration. The best results were obtained for p‐octyloxybenzyl derivatives against Staphylococcus epidermidis (minimal inhibitory concentrations = 32 μm).

Synthesis and biological evaluation of a new series of N-acyldiamines as potential antibacterial and antifungal agents

In continuation of our efforts to find new antimicrobial compounds, series of fatty N-acyldiamines were prepared from fatty methyl esters and 1,2-ethylenediamine, 1,3-propanediamine or 1,4-butanediamine. The synthesized compounds were screened for their antibacterial activity against Gram-positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and for their antifungal activity against four species of Candida (C. albicans, C. tropicalis, C. glabrata and C. parapsilosis). Compounds 5a (N-(2-aminoethyl)dodecanamide), 5b (N-(2-aminoethyl)tetracanamide) and 6d (N-(3-aminopropyl)oleamide) were the most active against Gram-positive bacteria, with MIC values ranging from 1 to 16μg/mL and were evaluated for their activity against 21 clinical isolates of methicillin-resistant S. aureus. All the compounds exhibited good to moderate antifungal activity. Compared to chloramphenicol, compound 6b displayed a similar activity (MIC50=16μg/mL). A positive correlation could be established between lipophilicity and biological activity.

In vitro antifungal activity of organic compounds derived from amino alcohols against onychomycosis

Onychomycosis is a fungal infection of the nail caused by high densities of filamentous fungi and yeasts. Treatment for this illness is long-term, and recurrences are frequently detected. This study evaluated in vitro antifungal activities of 12 organic compounds derived from amino alcohols against standard fungal strains, such as Trichophyton rubrum CCT 5507 URM 1666, Trichophyton mentagrophytes ATCC 11481, and Candida albicans ATCC 10231. The antifungal compounds were synthesized from p-hydroxybenzaldehyde (4a–4f) and p-hydroxybenzoic acid (9a–9f). Minimum inhibitory concentrations and minimum fungicidal concentrations were determined according to Clinical and Laboratory Standards Institute protocols M38-A2, M27-A3, and M27-S4. The amine series 4b–4e, mainly 4c and 4e compounds, were effective against filamentous fungi and yeast (MIC from 7.8 to 312 μg/mL). On the other hand, the amide series (9a–9f) did not present inhibitory effect against fungi, except amide 9c, which demonstrated activity only against C. albicans. This allowed us to infer that the presence of amine group and intermediate carbon number (8C–11C) in its aliphatic side chain seems to be important for antifungal activity. Although these compounds present cytotoxic activity on macrophages J774, our results suggest that these aromatic compounds might constitute potential as leader molecules in the development of more effective and less toxic analogs that could have considerable implications for future therapies of onychomycosis.

Brønsted Acid-Catalyzed Dipeptides Functionalization through Azlactones

Azlactones are useful building blocks in the synthesis of functional amino acid derivatives, heterocycles and bioactive molecules. In this work, a protocol for the organocatalytic functionalization of dipeptides has been presented. 2-Alkyl-substituted azlactone intermediates in the presence of different amines and alcohols were combined in a ring opening reaction approach. The products were synthesized in moderate to excellent isolated yields, providing new insights in peptide transformations involving carbodiimide activation.

Brønsted Acid-Catalyzed Epimerization-Free Preparation of Dual-Protected Amino Acid Derivatives

An organocatalytic protocol, employing the commercially available EDC as coupling agent, has been developed for the preparation of dual-protected amino acid derivatives without epimerization. This methodology was then applied to different Boc-amino acid and amine derivatives in moderate to excellent isolated yields. In addition, racemization-free Boc deprotection was also demonstrated. Mechanism investigation through electrospray ionization (+)-mass spectrometry/mass spectrometry revealed an acyclic intermediate (no azlactone formation) activated by the camphorsulfonic acid as an organocatalyst as a key step for the sequential attack of the nucleophile.

Diamine derivative anti-Trichomonas vaginalis and anti-Tritrichomonas foetus activities by effect on polyamine metabolism

Human and bovine trichomoniasis are sexually transmitted diseases (STD) caused by Trichomonas vaginalis and Tritrichomonas foetus, respectively. Human trichomoniasis is the most common non-viral STD in the world and bovine trichomoniasis causes significant economic losses to breeders. Considering the significant impact of the infections caused by these protozoa and the treatment failures, the search for new therapeutic alternatives becomes crucial. In this study the effect of diamines and amino alcohols in the in vitro viability of trichomonads was evaluated. Screening demonstrated the high activity of diamine 4 against these protozoa. Although cytotoxicity against HMVII cell line and slight hemolysis were observed in vitro, the compound showed no toxic effect on the Galleria mellonella in vivo model. Importantly, diamine 4 was active against both trichomonads species at 6h and 24h of incubation, and these effects was reverted by putrescine, a polyamine, suggesting competition for the same metabolic pathway. These findings indicate that the mechanism of action of diamine 4 is through the polyamine metabolism, a pathway distinct from that presented by metronidazole, the drug usually used to treat trichomoniasis and to which resistance is widely reported. These data demonstrate the importance of diamines as potential novel candidates as anti-T. vaginalis and anti-T. foetus agents.

RECENTES APLICAÇÕES EM SÍNTESE ORGÂNICA DE CATÁLISE FOTO REDOX MEDIADA POR LUZ VISÍVEL

In the past few years, photoredox catalysis has become a powerful tool in the field of organic synthesis. Using this efficient method, it is possible to excite organic compounds from visible light and attain alternative mechanistic pathways for the formation of chemical bonds, a result which is not obtainable by classical methods. The rapid growth of work in the area of photoredox catalysis is due to its low cost, broad chemical utility protocols, and, especially, its relevancy from the green and sustainable chemistry viewpoints. Thus, this study proposes a brief theoretical discussion of and highlights recent advances in visible-light-induced photoredox catalysis through the analysis of catalytic cycles and intermediates.