Stereoselective Synthesis of Indolyl‑<i>C</i>‑glycosides Enabled by Sequential Aminopalladation and Heck Glycosylation of 2‑Alkynylanilines with Glycals

An efficient and general approach for the synthesis of indolyl-C-glycosides via aminopalladation and subsequent Heck-type glycosylation of easily available 2-alkynylanilines and glycals has been developed. This protocol features excellent stereoselectivity, a broad substrate scope, and mild reaction conditions. In addition, 2,3-pseudoglycals also successfully participated in this cascade reaction, affording C2/C3-branched indolyl glycosides with high regio-/stereoselectivity. The utility of this protocol was also demonstrated by a large-scale reaction and diversified synthetic transformations of the desired products

Involvement of NADPH oxidase isoforms in the production of O_2⁻ manipulated by ABA in the senescing leaves of early-senescence-leaf (<i>esl</i>) mutant rice (<i>Oryza sativa</i>)

<div><p>In this study, the differences in reactive oxygen species (ROS) generation and abscisic acid (ABA) accumulation in senescing leaves were investigated by early-senescence-leaf (<i>esl</i>) mutant and its wild type, to clarify the relationship among ABA levels, ROS generation, and NADPH oxidase (Nox) in senescing leaves of rice (<i>Oryza sativa</i>). The temporal expression levels of <i>OsNox</i> isoforms in senescing leaves and their expression patterns in response to ABA treatment were determined through quantitative real-time reverse transcription PCR (qRT-PCR). Results showed that the flag leaf of the <i>esl</i> mutant generated more O_2^- concentrations and accumulated higher ABA levels than the wild-type cultivar did in the grain-filling stage. Exogenous ABA treatment induced O_2^- generation; however, it was depressed by diphenyleneiodonium chloride (DPI) pretreatment in the detached leaf segments. This finding suggested the involvement of NADPH oxidase in ABA-induced O_2^- generation. The <i>esl</i> mutant exhibited significantly higher expression of <i>OsNox2</i>, <i>OsNox5</i>, <i>OsNox6</i>, and <i>OsNox7</i> in the initial of grain-filling stage, followed by sharply decrease. The transcriptional levels of <i>OsNox1</i>, <i>OsNox3</i>, and <i>OsFR07</i> in the flag leaf of the <i>esl</i> mutant were significantly lower than those in the wild-type cultivar. The expression levels of <i>OsNox2</i>, <i>OsNox5</i>, <i>OsNox6</i>, and <i>OsNox7</i> were significantly enhanced by exogenous ABA treatments. The enhanced expression levels of <i>OsNox2</i> and <i>OsNox6</i> were dependent on the duration of ABA treatment. The inducible expression levels of <i>OsNox5</i> and <i>OsNox7</i> were dependent on ABA concentrations. By contrast, exogenous ABA treatment severely repressed the transcripts of <i>OsNox1</i>, <i>OsNox3</i>, and <i>OsFR07</i> in the detached leaf segments. Therefore, <i>OsNox2</i>, <i>OsNox5</i>, <i>OsNox6</i>, and <i>OsNox7</i> were probably involved in the ABA-induced O_2^- generation in the initial stage of leaf senescence. Subsequently, other oxidases activated in deteriorating cells were associated with ROS generation and accumulation in the senescing leaves of the <i>esl</i> mutant. Conversely, <i>OsNox1</i>, <i>OsNox3</i>, and <i>OsFR07</i> were not associated with ABA-induced O_2^- generation during leaf senescence.</p></div

Sequence of primers for <i>ACTIN</i> and <i>OsNox</i> isoform genes used for real-time quantitative polymerase chain reaction.

<p>Sequence of primers for <i>ACTIN</i> and <i>OsNox</i> isoform genes used for real-time quantitative polymerase chain reaction.</p

Temporal expression patterns of <i>OsNox1</i>, <i>OsNox3</i>, and <i>OsFR07</i> in the flag leaves of two rice cultivars in the grain-filling stage.

<p>Temporal expression patterns of <i>OsNox1</i>, <i>OsNox3</i>, and <i>OsFR07</i> in the flag leaves of two rice cultivars in the grain-filling stage.</p

Transcriptional analyses of <i>OsNox1</i>, <i>OsNox3</i>, and <i>OsFR07</i> in the detached leaf segments of two rice cultivars incubated at 10, 50, 100, and 500 μM ABA solutions for 6 h.

<p>Transcriptional analyses of <i>OsNox1</i>, <i>OsNox3</i>, and <i>OsFR07</i> in the detached leaf segments of two rice cultivars incubated at 10, 50, 100, and 500 μM ABA solutions for 6 h.</p

O_2^- production rate and ABA contents in the flag leaves of two rice cultivars in the grain-filling stage.

<p>Vertical bars represent standard errors (n = 3).</p

O_2^- production in detached leaf segments incubated by various concentrations of exogenous ABA solutions.

<p>Significant differences (p ≤ 0.05) between ABA doses are indicated by different letters.</p

Temporal expression patterns of <i>OsNox2</i>, <i>OsNox5</i>, <i>OsNox6</i>, and <i>OsNox7</i> in the flag leaves of two rice cultivars in the grain-filling stage.

<p>Temporal expression patterns of <i>OsNox2</i>, <i>OsNox5</i>, <i>OsNox6</i>, and <i>OsNox7</i> in the flag leaves of two rice cultivars in the grain-filling stage.</p

Sequence of primers for <i>ACTIN</i> and <i>OsNox</i> isoform genes used for real-time quantitative polymerase chain reaction.

<p>Sequence of primers for <i>ACTIN</i> and <i>OsNox</i> isoform genes used for real-time quantitative polymerase chain reaction.</p

Transcriptional analyses of <i>OsNox2</i>, <i>OsNox5</i>, <i>OsNox6</i>, and <i>OsNox7</i> in the detached leaf segments of two rice cultivars treated with exogenous ABA solutions.

<p>A, B, C, and D respectively indicate the comparison of the expression levels of <i>OsNox2</i>, <i>OsNox5</i>, <i>OsNox6</i>, and <i>OsNox7</i> treated with various concentrations of exogenous ABA solutions for 6 h; E, F, G, and H respectively illustrate the temporal expression patterns of <i>OsNox2</i>, <i>OsNox5</i>, <i>OsNox6</i>, and <i>OsNox7</i> treated with 100 μM exogenous ABA solution.</p