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Chemo- and Regioselective Functionalization of Nortrilobolide: Application for Semisynthesis of the Natural Product 2‑Acetoxytrilobolide

The difference in reactivity of the hexaoxygenated natural product thapsigargin (<b>1</b>) and the pentaoxygenated nortrilobolide (<b>3</b>) was compared in order to develop a chemo- and regioselective method for the conversion of nortrilobolide (<b>3</b>) into the natural product 2-acetoxytrilobolide (<b>4</b>). For the first time, a stereoselective synthesis of 2-acetoxytrilobolide (<b>4</b>) is described, which involves two key reactions: the first chemical step was a one-pot substitution–oxidation reaction of an allylic ester into its corresponding α,β-unsaturated ketone. The second process consisted of a stereoselective α′-acyloxylation of the key intermediate α,β-unsaturated ketone to afford its corresponding acetoxyketone, which was converted into 2-acetoxytrilobolide (<b>4</b>) in a few steps. This innovative approach would allow the synthesis of a broad library of novel and valuable penta- and hexaoxygenated guaianolides as potential anticancer agents

Dataset for: Sex differences but no evidence of quantitative honesty in the warning signals of six-spot burnet moths (Zygaena filipendulae L.)

The distinctive black and red wing pattern of six-spot burnet moths (Zygaena filipendulae, L.) is a classic example of aposematism, advertising their potent cyanide-based defences. While such warning signals provide a qualitatively honest signal of unprofitability, the evidence for quantitative honesty, whereby variation in visual traits could provide accurate estimates of individual toxicity, is more equivocal. Combining sophisticated measures of cyanogenic glucoside content and wing colour from the perspective of avian predators, we investigate the relationship between coloration and defences in Z. filipendulae, to test signal honesty both within and across populations. Mean cyanogenic glucoside concentration was not correlated with wing coloration across populations in males, yet in females higher cyanogenic glucoside levels were associated with smaller and lighter red forewing markings. Trends within populations were similarly indicative of quantitative dishonesty, and consistent differences between the sexes were apparent: larger females, carrying a greater total cyanogenic glucoside load, displayed larger but less conspicuous markings than smaller males, according to several colour metrics. The overall high aversiveness of cyanogenic glucosides and fluctuations in colour and toxin levels during an individual’s lifetime may contribute to these results, highlighting generally important reasons why signal honesty should not always be expected in aposematic species

Anchoring a Plant Cytochrome P450 via PsaM to the Thylakoids in <i>Synechococcus</i> sp. PCC 7002: Evidence for Light-Driven Biosynthesis

<div><p>Plants produce an immense variety of specialized metabolites, many of which are of high value as their bioactive properties make them useful as for instance pharmaceuticals. The compounds are often produced at low levels in the plant, and due to their complex structures, chemical synthesis may not be feasible. Here, we take advantage of the reducing equivalents generated in photosynthesis in developing an approach for producing plant bioactive natural compounds in a photosynthetic microorganism by functionally coupling a biosynthetic enzyme to photosystem I. This enables driving of the enzymatic reactions with electrons extracted from the photosynthetic electron transport chain. As a proof of concept, we have genetically fused the soluble catalytic domain of the cytochrome P450 CYP79A1, originating from the endoplasmic reticulum membranes of <i>Sorghum bicolor</i>, to a photosystem I subunit in the cyanobacterium <i>Synechococcus</i> sp. PCC 7002, thereby targeting it to the thylakoids. The engineered enzyme showed light-driven activity both <i>in vivo</i> and <i>in vitro</i>, demonstrating the possibility to achieve light-driven biosynthesis of high-value plant specialized metabolites in cyanobacteria.</p></div

Verification of product formation in living cells.

<p>A) Extracted ion chromatograms (<i>m/z</i> 152) from the LC-MS analysis of metabolites extracted from the growth medium of <i>Synechococcus</i> sp. PCC 7002 WT and PsaM-CYP79A1 cultures for detection of <i>in vivo</i> activity of the PsaM-CYP79A1 complex, compared to a <i>p</i>-hydroxyphenylacetaldoxime standard (C+). The two peaks are the E and Z isomers of the <i>p</i>-hydroxyphenylacetaldoxime. B) LC-MS extracted ion chromatograms as in A, from analysis of extracts of PsaM-CYP79A1 cyanobacteria or growth medium.</p

Sequences of oligonucleotide primers used in this study.

<p>Restriction sites inserted into the PCR product through the primers are underlined.</p

Iminolactones from <i>Schizophyllum commune</i>

Schizines A (<b>1</b>) and B (<b>2</b>), the first naturally occurring iminolactones (3,6-dihydro-2<i>H</i>-1,4-oxazin-2-one derivatives) to be reported, have been isolated from the fruiting bodies of <i>Schizophyllym commune</i>. In principle the 2-oxazinone moiety might have been formed by a reaction between the amino acid phenylalanine or tryptophan and an 2α-hydroxy-1-ketomarasmone. The alkaloids are unusual in that the carboxyl group of the amino acid precursor is preserved during the biosynthesis. The compounds showed some inhibition of the growth of cancer cells

Redirecting Photosynthetic Reducing Power toward Bioactive Natural Product Synthesis

In addition to the products of photosynthesis, the chloroplast provides the energy and carbon building blocks required for synthesis of a wealth of bioactive natural products of which many have potential uses as pharmaceuticals. In the course of plant evolution, energy generation and biosynthetic capacities have been compartmentalized. Chloroplast photosynthesis provides ATP and NADPH as well as carbon sources for primary metabolism. Cytochrome P450 monooxygenases (P450s) in the endoplasmic reticulum (ER) synthesize a wide spectrum of bioactive natural products, powered by single electron transfers from NADPH. P450s are present in low amounts, and the reactions proceed relatively slowly due to limiting concentrations of NADPH. Here we demonstrate that it is possible to break the evolutionary compartmentalization of energy generation and P450-catalyzed biosynthesis, by relocating an entire P450-dependent pathway to the chloroplast and driving the pathway by direct use of the reducing power generated by photosystem I in a light-dependent manner. The study demonstrates the potential of transferring pathways for structurally complex high-value natural products to the chloroplast and directly tapping into the reducing power generated by photosynthesis to drive the P450s using water as the primary electron donor

Localization of PsaM in PSI and schematic drawing of the thylakoid in the engineered strain.

<p>A) and B) The crystal structure of a monomer of photosystem I from the cyanobacterium <i>Thermosynechococcus elongatus</i> seen from the cytoplasmic side of the thylakoid membrane (A) and from the trimer-facing side of the monomer (B). RCSB Protein Data Bank ID: 1JB0. The PsaM subunit is shown in green in both panels and additionally indicated by an arrow in panel A. C) Schematic representation of the PsaM-CYP79A1 fusion protein in the thylakoid membrane.</p

Localization of the PsaM-CYP79A1 fusion protein in the thylakoids.

<p>A) Immunoblot of proteins from 80 µL of the 0.5 mL fractions collected from the PsaM-CYP79A1 sucrose gradient shown in panel B), concentrated through acetone precipitation. Antibodies against the PSI subunit PsaC (∼9 kDa), the PSII subunit PsbA (∼32 kDa) and the CYP79A1 (∼61 kDa) have been used. CYP79A1, d.e.: digitally enhanced representation of the chemiluminescence signal detected from the CYP79A1 bands (shown below). C+: CYP79A1 expressed in chloroplasts of tobacco. Fraction 1 is the bottommost and fraction 28 the topmost fraction in the gradient. B) Sucrose gradients separating the components of WT and PsaM-CYP79A1 thylakoids solubilized in 1% (w/v) β-DM. C) Separation of protein complexes of β-DM-solubilized WT and PsaM-CYP79A1 thylakoids by BN-PAGE.</p