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 NH₄Cl

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>_s^Extract) 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>_s^Extract value (1.26 × 10^–2 M^–1 s^–1) of Nipponbare (extract 1) with the highest activity was 1.5 times larger than that (8.29 × 10^–3) 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>_s^Extract) (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>_s^{AOH‑<i>i</i>} [AOH-<i>i</i>]/10⁵} of the rate constant (<i>k</i>_s^{AOH‑<i>i</i>}) and the concentration ([AOH-<i>i</i>]/10⁵) 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>_s^Extract 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 (¹O₂) quenching rates (<i>k</i>_Q (<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>_Q (<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 ¹O₂-quenching activity.</p> <p>Measurements of the quenching rate (<i>k</i>_Q) of singlet oxygen were performed for seven rice bran extracts in ethanol to evaluate their singlet oxygen quenching activity.</p