7 research outputs found
Concise Syntheses of Hyrtioreticulins C and D via a C‑4 Pictet–Spengler Reaction: Revised Signs of Specific Rotations
The first syntheses of hyrtioreticulins
C and D via a Pictet–Spengler reaction at the C-4 position
of the indole rings are described. The synthesis proceeds in only
two steps from commercially available starting materials. In this
Communication, the structures of the natural products were confirmed.
Furthermore, we revise the signs of the specific rotations of hyrtioreticulins
C and D
2‑Hydroxyindoline-3-triethylammonium Bromide: A Reagent for Formal C3-Electrophilic Reactions of Indoles
A novel indole-2,3-epoxide
equivalent, 2-hydroxyindoline-3-triethylammonium
bromide, was found to be a convenient reagent for formal C3-electrophilic
reactions of indoles with various nucleophiles. By taking advantage
of the nucleophilic character of the oxygen of the 2-hydroxyindoline,
the interrupted retro-Claisen and interrupted Feist–Bénary
reactions with 1,3-dicarbonyl compounds were efficiently achieved
2‑Hydroxyindoline-3-triethylammonium Bromide: A Reagent for Formal C3-Electrophilic Reactions of Indoles
A novel indole-2,3-epoxide
equivalent, 2-hydroxyindoline-3-triethylammonium
bromide, was found to be a convenient reagent for formal C3-electrophilic
reactions of indoles with various nucleophiles. By taking advantage
of the nucleophilic character of the oxygen of the 2-hydroxyindoline,
the interrupted retro-Claisen and interrupted Feist–Bénary
reactions with 1,3-dicarbonyl compounds were efficiently achieved
Double “Open and Shut” Transformation of γ‑Carbolines Triggered by Ammonium Salts: One-Pot Synthesis of Multiheterocyclic Compounds
A novel
cascade reaction of indole-2,3-epoxide equivalents with
γ-carbolines by utilizing a double “open and shut”
transformation to access multiheterocyclic compounds containing both
isotryptamines and pyrimido[1,6-<i>a</i>]indoles has been
developed. This strategy utilizes the in situ formation of a bulky
quaternary ammonium salt via ammonium exchange, which undergoes Hofmann
elimination/vinylogous Mannich/retro-Mannich/cyclization cascade sequences
One-Pot Construction of 3,3′-Bisindolylmethanes through Bartoli Indole Synthesis
A one-pot approach to 3,3′-bisindolylmethane derivatives from nitrobenzene derivatives through the Bartoli indole synthesis was developed, in which the acid used to quench the reaction markedly affected its outcome. Quenching the reaction with concd HCl produced 3,3′-bisindolylmethane in contrast to the formation of 7-substituted indole by quenching with NH<sub>4</sub>Cl
Kinetic Study of the Scavenging Reaction of the Aroxyl Radical by Seven Kinds of Rice Bran Extracts in Ethanol Solution. Development of an Aroxyl Radical Absorption Capacity (ARAC) Assay Method
Recently,
a new assay method that can quantify the aroxyl radical
(ArO•) absorption capacity (ARAC) of antioxidants (AOHs) was
proposed. In the present work, the second-order rate constants (<i>k</i><sub>s</sub><sup>Extract</sup>) and ARAC values for the
reaction of ArO• with seven kinds of rice bran extracts 1–7,
which contain different concentrations of α-, β-, γ-,
and δ-tocopherols and -tocotrienols (α-, β-, γ-,
and δ-Tocs and -Toc-3s) and γ-oryzanol, were measured
in ethanol at 25 °C using stopped-flow spectrophotometry. The <i>k</i><sub>s</sub><sup>Extract</sup> value (1.26 × 10<sup>–2</sup> M<sup>–1</sup> s<sup>–1</sup>) of Nipponbare
(extract 1) with the highest activity was 1.5 times larger than that
(8.29 × 10<sup>–3</sup>) of Milyang-23 (extract 7) with
the lowest activity. The concentrations (in mg/100 g) of α-,
β-, γ-, and δ-Tocs and -Toc-3s and γ-oryzanol
found in the seven extracts 1–7 were determined using HPLC-MS/MS
and UV–vis absorption spectroscopy, respectively. From the
results, it has been clarified that the ArO•-scavenging rates
(<i>k</i><sub>s</sub><sup>Extract</sup>) (that is, the relative
ARAC value) obtained for the seven extracts 1–7 may be approximately
explained as the sum of the product {Σ <i>k</i><sub>s</sub><sup>AOH‑<i>i</i></sup> [AOH-<i>i</i>]/10<sup>5</sup>} of the rate constant (<i>k</i><sub>s</sub><sup>AOH‑<i>i</i></sup>) and the concentration ([AOH-<i>i</i>]/10<sup>5</sup>) of AOH-<i>i</i> (Tocs, Toc-3s,
and γ-oryzanol) included in rice bran extracts. The contribution
of γ-oryzanol to the <i>k</i><sub>s</sub><sup>Extract</sup> value was estimated to be between 3.0–4.7% for each extract.
Taken together, these results suggest that the ARAC assay method is
applicable to general food extracts
Kinetic study of the quenching reaction of singlet oxygen by seven rice bran extracts in ethanol solution. Development of a singlet oxygen absorption capacity (SOAC) assay method
<p>Measurements of singlet oxygen (<sup>1</sup>O<sub>2</sub>) quenching rates (<i>k</i><sub>Q</sub> (<i>S</i>)) and the relative singlet oxygen absorption capacity (SOAC) values were performed for seven rice bran extracts 1–7, which contained different concentrations of antioxidants (AOs) (such as α-, β-, γ-, and δ-tocopherols and -tocotrienols, three carotenoids (lutein, β-carotene, and zeaxanthin), and γ-oryzanol), in ethanol at 35 °C using UV–vis spectrophotometry. The concentrations of four tocopherols and four tocotrienols, three carotenoids, and γ-oryzanol contained in the extracts were determined using HPLC-MS/MS, UV-HPLC, and UV–vis absorption spectroscopy, respectively. Furthermore, comparisons of <i>k</i><sub>Q</sub> (<i>S</i>) (Obsd.) values observed for the above extracts 1–7 with the sum of the product { [AO-<i>i</i>]} of the values obtained for each AO-<i>i</i> and the concentration ([AO-<i>i</i>]) of AO-<i>i</i> contained in extracts 1–7 were performed. From the results, it has been ascertained that the SOAC method is applicable to general food extracts to evaluate their <sup>1</sup>O<sub>2</sub>-quenching activity.</p> <p>Measurements of the quenching rate (<i>k</i><sub>Q</sub>) of singlet oxygen were performed for seven rice bran extracts in ethanol to evaluate their singlet oxygen quenching activity.</p