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Studies toward the total synthesis of dihydrolycolucine. Preparation of AB and CEF ring fragments.

ABSTRACT: A strategy for the synthesis of the lycopodium alkaloid dihydrolycolucine (1) has been investigated. Synthetic routes were developed based on N-acylpyridinium salt chemistry to prepare target fragments 3 and 4 that could ultimately converge to the natural product. Key reactions include IMDA cycloadditions and retro-Mannich ring-openings to form both the AB and the EF ring fragments. The ring C precursor was prepared using pyridine substitution and directed lithiation chemistry. A Suzuki cross-coupling of rings C and EF led to the CEF ring fragment. Initial attempts at closure of the seven-membered D ring were unsuccessful.

SUBMITTER: Cash BM

PROVIDER: S-EPMC4066915 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Studies towards the total synthesis of drimentine C. Preparation of the AB and CDEF ring fragments.

Project description:The drimentine family is a class of hybrid isoprenoids derived from actinomycete bacteria. Members of this family display weak antitumor and antibacterial activity. Herein we report our efforts toward the total synthesis of drimentine C using three distinct approaches incorporating palladium-catalyzed cyanoamidation, reductive cross-coupling, and photoredox-catalyzed α-alkylation of an aldehyde as key steps. Our synthetic efforts use a convergent synthesis to assemble the terpenoid and alkaloid portions of drimentine C from readily available l-tryptophan, l-proline, and (+)-sclareolide.

| S-EPMC7567177 | biostudies-literature

Studies toward the AB ring system of the tetrapetalone natural products.

Project description:Synthetic efforts toward the rapid assembly of the AB ring system of the tetrapetalones is described. Key to this work was the use of [3+2] cycloaddition/oxidative extrusion methodology to furnish functionalized aryl enones. The Nazarov cyclization of these substrates was examined, and optimized to generate the AB ring carbon skeleton. Then, Pd-catalyzed cross-coupling were conducted, and conditions were identified that enabled installation of the requisite C14-N bond.

| S-EPMC4542023 | biostudies-literature

Studies toward the total synthesis of pluraflavin A.

Project description:A synthetic strategy towards the potent cytostatic agent pluraflavin A has been developed. Formation of the enantioenriched anthrapyran core bearing a halogen atom enabled the introduction of the ??C-aryl glycoside by Stille cross-coupling and subsequent hydrogenation of the aryl glycal. Chemo- and stereoselective O-glycosylations of ??oliose and ??3-epi vancosamine residues afforded a fully glycosylated aromatic core. Attempts to install the dimethylamino group of the C-disaccharide suggest that introduction of an azide group by displacement and subsequent reduction may pave the way to the total synthesis of pluraflavin A.

| S-EPMC4795151 | biostudies-literature

Toward the Total Synthesis of Alpkinidine: Michael Addition to Isoquinolinetrione CE Ring-System Synthons.

Project description:Strategies toward the total synthesis of the marine pyrroloacridine alkaloid alpkinidine have been explored, focusing on linking quinonoid CE ring-system synthons with the A ring, followed by condensation to form the B and D rings. The key Michael addition of the ester enolate derived from ethyl o-nitrophenylacetate to 2-methylisoquinoline-1,5,8(2H)-trione proceeded with the wrong regiochemistry. This issue was addressed by incorporating the D-ring nitrogen at an earlier stage, affording advanced intermediates possessing the complete carbon skeleton of alpkinidine. However, attempts to close the D and B rings were unsuccessful. The novel isoquinolinetriones reported here, and the general strategy of connecting CE- and A-ring synthons through Michael additions, may be useful in the synthesis of other pyrrolo- and pyridoacridines, in particular the anticancer lead neoamphimedine and analogues.

| S-EPMC9202020 | biostudies-literature

Toward the Total Synthesis of Alpkinidine: Synthesis of Haloquinone CE Ring System Synthons and Attempted Nucleophilic Bisannulation.

Project description:Model chemistry involving the bisannulation of 2,3-dichloro-1,4-naphthoquinone with the ester enolate derived from ethyl o-nitrophenylacetic acid, which rapid assembled the ABCD ring system of a pentacyclic pyrroloacridine, has been applied to the attempted synthesis of the marine natural product alpkinidine. The reaction of ethyl o-nitrophenylacetic acid with 6,7-dichloro-2-methylisoquinoline-1,5,8(2H)-trione, required to extend the model strategy to alpkinidine, was unfruitful, giving only complex mixtures. Efforts to direct the regiochemistry of the key Michael substitution step using 6-bromo-2-methylisoquinoline-1,5,8(2H)-trione afforded an adduct sharing the complete carbon skeleton of alpkinidine, but this could not be elaborated to the natural product.

| S-EPMC9202046 | biostudies-literature

Total Synthesis and Structural Studies of Zwitterionic <i>Bacteroides fragilis</i> Polysaccharide A1 Fragments.

Project description:Zwitterionic polysaccharides (ZPSs) are exceptional carbohydrates, carrying both positively charged amine groups and negatively charged carboxylates, that can be loaded onto MHC-II molecules to activate T cells. It remains enigmatic, however, how these polysaccharides bind to these receptors, and to understand the structural features responsible for this "peptide-like" behavior, well-defined ZPS fragments are required in sufficient quantity and quality. We here present the first total synthesis of Bacteroides fragilis PS A1 fragments encompassing up to 12 monosaccharides, representing three repeating units. Key to our successful syntheses has been the incorporation of a C-3,C-6-silylidene-bridged "ring-inverted" galactosamine building block that was designed to act as an apt nucleophile as well as a stereoselective glycosyl donor. Our stereoselective synthesis route is further characterized by a unique protecting group strategy, built on base-labile protecting groups, which has allowed the incorporation of an orthogonal alkyne functionalization handle. Detailed structural studies have revealed that the assembled oligosaccharides take up a bent structure, which translates into a left-handed helix for larger PS A1 polysaccharides, presenting the key positively charged amino groups to the outside of the helix. The availability of the fragments and the insight into their secondary structure will enable detailed interaction studies with binding proteins to unravel the mode of action of these unique oligosaccharides at the atomic level.

| S-EPMC10311536 | biostudies-literature

Studies toward the synthesis of spirolides: assembly of the elaborated E-ring fragment.

Project description:A stereoselective synthesis of the spiroimine fragment of spirolide C is described. The congested C7 and C29 tertiary and quaternary centers are constructed by a diastereoselective Ireland-Claisen rearrangement. The E ring is completed by means of an aldol cyclocondensation. Additional studies were preformed on the advanced intermediate to probe a future coupling strategy.

| S-EPMC2756537 | biostudies-literature

A preparation of murine liver fragments for in vitro studies: liver preparation for toxicological studies.

Project description:BackgroundThe aim of this study was to develop liver tissue preparation suitable for investigating toxins. Hepatocyte respiration, ATP content, urea synthesis, caspase activity and morphology were measured as a function of in vitro incubation time. Mice were anesthetized by sevoflurane inhalation. Small liver fragments were then rapidly excised and incubated at 37°C in Krebs-Henseleit buffer (continuously gassed with 95% O2: 5% CO2) for up to 6 h. Phosphorescence O2 analyzer was used to determine the rate of cellular mitochondrial O2 consumption (kc, μM O2 min-1 mg-1). Cellular ATP was measured using the luciferin/luciferase system. The caspase-3 substrate N-acetyl-asp-glu-val-asp-7-amino-4-methylcoumarin (Ac-DEVD-AMC) was used to monitor intracellular caspase activity; cleaved AMC moieties (reflecting caspase activity) were separated on HPLC and detected by fluorescence.FindingsRespiration was inhibited by cyanide, confirming the oxidation occurred in the respiratory chain. The values of kc (mean ± SD) for 0≤ t ≤6 h were 0.15 ± 0.02 μM O2 min-1 mg-1 (n = 18, coefficient of variation, CV = 13%), ATP content 131 ± 69 pmol mg-1 (1≤ t ≤6 h, n = 16, CV = 53%), synthesized urea 0.134 ± 0.017 mg/dL mg-1 in 50 min (0≤ t ≤6 h, n = 14, CV = 13%), and AMC peak area 62,540 ± 26,227 arbitrary units mg-1 (1≤ t ≤6 h, n = 3, CV = 42%). Hepatocyte morphology and organelles were reasonably persevered.ConclusionsThe described liver tissue preparation demonstrates stable hepatocyte structure, ultrastructure and biomarkers for up to 6 h, permitting in vitro studies.

| S-EPMC3598918 | biostudies-literature

Toward the Total Synthesis of Scleritodermin A: Preparation of the C(1)-N(15) Fragment.

Project description:The synthesis of the C(1)-N(15) fragment of the marine natural product Scleritodermin A has been accomplished through a short and stereocontrolled sequence. Highlights of this route include the synthesis of the novel ACT fragment and the formation of the alpha-keto amide linkage by the use of a highly activated alpha, beta-ketonitrile.

| S-EPMC1832122 | biostudies-literature

Studies toward the first stereoselective total synthesis of (±)-quinolizidine 195C and other transformations.

Project description:Starting from a thio-substituted 4-quinolizidinone, a series of C-6 alkylated derivatives with a trans C-6, C-9a relationship was synthesized. Further transformations led to the first stereoselective total synthesis of the structure proposed for (±)-quinolizidine 195C, the major alkaloid isolated from the skin extracts of the Madagascan frog Mantella betsileo. Since the spectral data of the synthetic and natural products differed significantly, the true structure of (±)-quinolizidine 195C remains uncertain.

| S-EPMC6269906 | biostudies-literature

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