Caroline C. S. Gonçalves

6-Alkyl-3,4-dihydro-2H-pyrans: Chemical Secretion Compounds in Neotropical Harvestmen

The defensive secretions of five neotropical species of harvestmen (Opiliones: Gonyleptidae) from the Brazilian Atlantic Forest were analyzed and chemically characterized by GC-MS and NMR methods. Three of the species, Cobania picea, Roweria virescens, and Serracutisoma proximum, secrete a mixture of 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone. The secretions produced by the other two species, Iporangaia pustulosa and Neosadocus maximus, contain 1-hepten-3-one, 5-methyl-1-hexen-3-one, and 1-(6-butyl-3,4-dihydro-2H-pyran-2-yl)pentanone (1) as major components, as well as 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone as minor constituents. The dihydropyran 1-(6-butyl-3,4-dihydro-2H-pyran-2-yl)pentanone (1) is a new natural product, composed of two 1-hepten-3-one subunits formally linked in a hetero-Diels-Alder reaction. The natural product was proven to be racemic, and its biogenetic origin is discussed.

Additional Vinyl Ketones and Their Pyranyl Ketones in Gonyleptid Harvestmen (Arachnida: Opiliones) Suggest These Metabolites Are Widespread in This Family

Four species of gonyleptid harvestmen, Acanthogonyleptes pulcher, Gonyleptes saprophilus (Gonyleptinae), Sodreana barbiellini, and Sodreana leprevosti (Sodreaninae), were examined by GC-MS and ¹³H NMR. All of these species release vinyl ketones, and three of them produce the corresponding pyranyl ketones, which are presumed hetero-Diels-Alder (HDA) dimers. The vinyl ketones 5-methyl-1-hexen-3-one, rac-4-methyl-1-hexen-3-one, and (S)-4-methyl-1-hexen-3-one were synthesized. Natural 4-methyl-1-hexen-3-one is present as a single stereoisomer and has the R-configuration. Vinyl ketone dimers (HDA dimers) were also observed in the scent gland exudate and characterized by HRMS, ¹³C NMR, and ¹H NMR chemical shifts of the pyranyl moiety.

Synthesis of the C1-C9 fragment of the potent antitumor agent dictyostatin

We describe herein a short and efficient synthesis of the C1-C9 fragment of the potent antitumor agent dictyostatin. Notable features of this approach include a Sharpless asymmetric epoxidation followed by epoxide opening under Myashitas conditions to introduce the stereogenic centers at C6 and C7, and a Horner-Wadsworth-Emmons type reaction under Andos conditions to construct the Z-double bond of the 1,3-(Z,E)-diene system.

Total synthesis of (-)-basiliskamide A and NMR studies on the conversion of basiliskamide A to basiliskamide B

We describe herein our approach to the total synthesis of the antifungal polyketide (-)-basiliskamide A, as well as 1H NMR studies on the migration of the cinnamoyl side chain of basiliskamide A to form basiliskamide B in CDCl3 solution.

High Throughput Enzymatic Enantiomeric Excess: Quick-ee

High throughput techniques to evaluate enantiomeric excess (ee) and enantiomeric ratio (E) of enzymatic reactions are fast and efficient tools that can be applied large quantities of enzymes, microorganisms and clones. The Quick-ee technique proposed in this study produces the ee and conversion values separately.

Monitorando atividades enzimáticas com sondas fluorogênicas

Latent fluorogenic probes are essential tools for molecular and chemical biology, providing valuable information about enzymatic activity and occurrence. In this review, a brief outline of fluorophores and latent fluorogenic probes is given. Furthermore, advances and challenges in the development of fluorogenic chemical probes to visualize enzymatic activities (hydrolases and oxidoreductases) of biotechnological and biomedical interest are highlighted, including some methodologies for intracellular imaging.

Simultaneous Multienzymatic Screening with Fluorogenic Probes

The simultaneous screening of multiple enzyme activities in a single assay has numerous advantages over the traditional format, since it decreases sampling errors, allows savings in reagents and consumables and reduces the time and labor required to conduct the assays. In the present study, a direct and sensitive assay for the simultaneous detection of epoxide hydrolase and esterase (or lipase) activities was developed. Signal overlap is avoided by synthesizing fluorogenic probes with enzyme-specific alkyl linkers, connected to different fluorophores (resorfurin and umbelliferone), which exhibit emission spectra at different wavelengths. The simultaneous assays were conducted in microplate format with the fluorogenic probes monitored in the same well that uses microorganisms as enzyme source. Our results show that the fluorescent signal from each of the probes used here can be discriminated, allowing multiple enzyme activity detection and quantitation.