Indole Precursors Research Articles

The natural history of intraductal papillary mucinous neoplasm of the pancreas: Reappraisal of the indolent precursor of pancreatic cancer

Aim: Aim of the present study is to describe the natural history of IPMNs observed at a high-volume center for thirty years. Methods: Growth rates were analyzed through a linear-mixed model. The development of worrisome features (WF), high-risk stigmata (HRS), pancreatic cancer (PC), survival and risk for surgery were analyzed. Results: From a total of 2189 observed patients, 1529 were included. The overall growth rate was 1mm/year. For about half of cases no dimensional change was documented. The presence of high risk stigmata (HRS), age < 75 years, and cyst size >30mm at diagnosis were associated to a faster growth rate. During follow-up, IPMNs developed WF in 6.5% of cases and HRS in 0.6%. Overall, 3.5% of patients developed PC after a median time of 28 months. Of these PC patients, 72% previously developed HRS/WF. Of 1043 initially observed indolent branch duct (BD) IPMNs, 16 eventually developed PC with 10% occurring after 15 years of follow-up. HRS and growth rate were independent predictors of PC. Growth rate was the only difference between IPMNs developing PC and those remained stable after more than 5 years of follow-up (n=399). The mean estimated disease specific survival (DSS) for the overall population exceeded 19 years. Conclusions: IPMN of the pancreas is the indolent precursor of PDAC that will not show a detectable growth during follow-up in half of the cases. Those rapidly growing (>2.75 mm/year) will likely progress to pancreatic cancer through the development of WF and HRS during the first year of follow-up.

The natural history of intraductal papillary mucinous neoplasms of the pancreas: Reappraisal of the indolent precursor of pancreatic cancer

Pancreatic mucinous cystic neoplasms (MCN) are rare tumors that are usually diagnosed in females.In our department, only four of the 109 consecutive cases of pancreatic tumors (3.67%) were diagnosed as MCNs. In this report, we present the characteristics of these four specific cases which also showed unusual HER-2 positivity and neuroendocrine differentiation.The four MCNs were diagnosed in patients with ages between 46 and 75 years. Other clinical particularities were the following: one benign case, splenic rupture as result of a giant cystic tumor on the tail of the pancreas directly invading the spleen in the second one, metastases in the accessory spleen in the third one and invasion of the abdominal vessels in the fourth case. In all of these cases, the ovarian-like stroma tested positivity for calretinin, progesterone receptor (PR) and, in cases 2 and 3, for AE1/AE3 keratin. The malignant tumor cells were marked by carcinoembryonic antigen, HER-2, maspin, PR and the neuroendocrine markers synaptophysin, CD56, and neuron-specific enolase.These cases highlight the unusually aggressive behavior of pancreatic MCN with invasive carcinomas that share mixed exo- and endocrine components and show epithelial-mesenchymal transition.

Engineering 'Golden' Fluorescence by Selective Pressure Incorporation of Non-canonical Amino Acids and Protein Analysis by Mass Spectrometry and Fluorescence

Fluorescent proteins are fundamental tools for the life sciences, in particular for fluorescence microscopy of living cells. While wild-type and engineered variants of the green fluorescent protein from Aequorea victoria (avGFP) as well as homologs from other species already cover large parts of the optical spectrum, a spectral gap remains in the near-infrared region, for which avGFP-based fluorophores are not available. Red-shifted fluorescent protein (FP) variants would substantially expand the toolkit for spectral unmixing of multiple molecular species, but the naturally occurring red-shifted FPs derived from corals or sea anemones have lower fluorescence quantum yield and inferior photo-stability compared to the avGFP variants. Further manipulation and possible expansion of the chromophore's conjugated system towards the far-red spectral region is also limited by the repertoire of 20 canonical amino acids prescribed by the genetic code. To overcome these limitations, synthetic biology can achieve further spectral red-shifting via insertion of non-canonical amino acids into the chromophore triad. We describe the application of SPI to engineer avGFP variants with novel spectral properties. Protein expression is performed in a tryptophan-auxotrophic E. coli strain and by supplementing growth media with suitable indole precursors. Inside the cells, these precursors are converted to the corresponding tryptophan analogs and incorporated into proteins by the ribosomal machinery in response to UGG codons. The replacement of Trp-66 in the enhanced "cyan" variant of avGFP (ECFP) by an electron-donating 4-aminotryptophan results in GdFP featuring a 108 nm Stokes shift and a strongly red-shifted emission maximum (574 nm), while being thermodynamically more stable than its predecessor ECFP. Residue-specific incorporation of the non-canonical amino acid is analyzed by mass spectrometry. The spectroscopic properties of GdFP are characterized by time-resolved fluorescence spectroscopy as one of the valuable applications of genetically encoded FPs in life sciences.

Engineering 'Golden' Fluorescence by Selective Pressure Incorporation of Non-canonical Amino Acids and Protein Analysis by Mass Spectrometry and Fluorescence.

Fluorescent proteins are fundamental tools for the life sciences, in particular for fluorescence microscopy of living cells. While wild-type and engineered variants of the green fluorescent protein from Aequorea victoria (avGFP) as well as homologs from other species already cover large parts of the optical spectrum, a spectral gap remains in the near-infrared region, for which avGFP-based fluorophores are not available. Red-shifted fluorescent protein (FP) variants would substantially expand the toolkit for spectral unmixing of multiple molecular species, but the naturally occurring red-shifted FPs derived from corals or sea anemones have lower fluorescence quantum yield and inferior photo-stability compared to the avGFP variants. Further manipulation and possible expansion of the chromophore's conjugated system towards the far-red spectral region is also limited by the repertoire of 20 canonical amino acids prescribed by the genetic code. To overcome these limitations, synthetic biology can achieve further spectral red-shifting via insertion of non-canonical amino acids into the chromophore triad. We describe the application of SPI to engineer avGFP variants with novel spectral properties. Protein expression is performed in a tryptophan-auxotrophic E. coli strain and by supplementing growth media with suitable indole precursors. Inside the cells, these precursors are converted to the corresponding tryptophan analogs and incorporated into proteins by the ribosomal machinery in response to UGG codons. The replacement of Trp-66 in the enhanced "cyan" variant of avGFP (ECFP) by an electron-donating 4-aminotryptophan results in GdFP featuring a 108 nm Stokes shift and a strongly red-shifted emission maximum (574 nm), while being thermodynamically more stable than its predecessor ECFP. Residue-specific incorporation of the non-canonical amino acid is analyzed by mass spectrometry. The spectroscopic properties of GdFP are characterized by time-resolved fluorescence spectroscopy as one of the valuable applications of genetically encoded FPs in life sciences.

Biosynthesis of the Klebsiella oxytoca Pathogenicity Factor Tilivalline: Heterologous Expression, in Vitro Biosynthesis, and Inhibitor Development.

Tilvalline is a pyrrolo[4,2]benzodiazepine derivative produced by the pathobiont Klebsiella oxytoca and is the causative toxin in antibiotic associated hemorrhagic colitis (AAHC). Heterologous expression of the tilivalline biosynthetic gene cluster along with in vitro reconstitution of the respective NRPS (NpsA, ThdA, NpsB) was employed to reveal a nonenzymatic indole incorporation via a spontaneous Friedel-Crafts-like alkylation reaction. Furthermore, the heterologous system was used to generate novel tilivalline derivatives by supplementation of respective anthranilate and indole precursors. Finally, it could be shown that salicylic and acetylsalicylic acid inhibit the biosynthesis of tilivalline in K. oxytoca liquid culture, presumably by blocking the peptidyl carrier protein ThdA, pointing toward a potential application in combination therapy to prevent or alleviate the symptoms of AAHC.

Cascade Synthesis of 3-Functionalized Indoles from Nitrones and Their Conversion to Cycloheptanone-Fused Indoles.

A cascade reaction of N-aryl-α,β-unsaturated nitrones and electron-deficient allenes has been discovered that allows single-step access to 3-functionalized indoles that usually require preformation and alkylation of an indole precursor. The heterocycles prepared through the hydrogen bond donor catalyzed cascade reaction are poised to undergo a McMurry coupling to form previously synthetically elusive cycloheptanone-fused indoles. The scope of these transformations is discussed as well as mechanistic experiments describing proposed intermediates of the cascade reaction and an initial catalytic asymmetric example that generates a carbon stereocenter during the cascade process.

AL Amyloidoma of the Skin/Subcutis: Cutaneous Amyloidosis, Plasma Cell Dyscrasia or a Manifestation of Primary Cutaneous Marginal Zone Lymphoma?

It is unclear whether AL amyloidoma of the skin/subcutis represents a distinct entity, an indolent precursor of systemic amyloidosis, or a manifestation of cutaneous marginal zone lymphoma (cMZL). We collected 10 cases of cutaneous AL amyloidoma in order to better characterize the clinicopathologic features of this elusive entity (M:F=4:6; median age: 62.5 y, range: 31 to 82 y). Nine patients had a solitary nodule or plaque on the lower extremity (n=7), upper extremity (n=1), or chin (n=1). One patient had an AL amyloidoma on the right thigh and a second lesion on the right arm showing histopathologic features of cMZL without amyloid deposits. Clinical investigations excluded relevant systemic disease in all cases. Microscopically, dermal/subcutaneous deposits of amyloid were associated with sparse to moderate perivascular infiltrates of lymphocytes and monotypic plasma cells (7 with kappa and 3 with lambda light chain restriction). The plasma cells expressed CD56 in one of 9 studied cases. One case was characterized by a t(14;18)(q32;q21)/IGH-MALT1 translocation. Follow-up was available in 8 cases. All remain systemically well after a median time of 86.5 months (range: 40 to 144 mo). Local recurrence of disease was observed in 3 patients. A fourth patient presented with a cMZL without amyloid deposits 8 years after excision of the cutaneous AL amyloidoma. Although our series is small, careful categorization and follow-up of the cases, together with updated information in the literature, show clinical and biological links between AL amyloidomas of the skin/subcutis and cMZL, suggesting that at least a subset of cutaneous AL amyloidoma may represent an unusual manifestation of cMZL (cutaneous mucosa-associated lymphoid tissue lymphomas).

Biosynthesis of indigo in Escherichia coli expressing self-sufficient CYP102A from Streptomyces cattleya

Cytochrome P450 monooxygenases (CYP) are a superfamily of heme-thiolate proteins which catalyze the incorporation of oxygen atoms into substrates. Here, a self-sufficient CYP102A from Streptomyces cattleya (CYP102A_scat) was cloned, produced recombinantly in Escherichia coli strain BL21 (DE3), and the characteristic features were investigated. However, unlike other self-sufficient CYP102A enzymes that have been reported, CYP102A_scat was found to be able to catalyze intracellular hydroxylation of indole molecules with 3-C specific regioselectivity. Consequently, E. coli strains producing CYP102A_scat could synthesize approximately 1.0 g/L of indigo in LB media. Optimization of indigo synthesis was investigated through additional feeding of indole precursors such as glucose, l-tryptophan, and indole. Indigo production reached up to 3.8 ± 0.1 g/L by adding 20 μM of extracellular indole and 0.2 mM of l-tryptophan to the LB media. To our knowledge, this is a record and the highest yield achieved so far.

Identification of azepinone fused tetracyclic heterocycles as new chemotypes with protein kinase inhibitory activities

The design and synthesis of small tetracyclic heterocycles which bear two new regioisomeric 2-carboxyethyl-1H-pyrrole-annulated indoloazepinone scaffolds is described. An azepinone motif, which is inherent in the structures of many well studied protein kinase inhibitors, serves as prominent structural feature of the new compounds. Concise access to the new regioisomeric tetracyclic derivatives was accomplished through amide coupling of appropriate pyrrole and indole precursors followed by an intramolecular Heck coupling reaction of the intermediate amide conjugates. Preliminary evaluation of newly synthesized tetracyclic molecules against a panel of protein kinases indicated their inhibitory activities and revealed promising selectivity profiles. The new compounds displayed no significant antiproliferative activity against MCF-7 cancer cells. Interestingly, derivative 19a exhibited selective TAK1 kinase inhibitory activity and figures as a promising chemotype for the discovery of new TAK1 inhibitors.

ChemInform Abstract: Strychnine as Target, Samarium Diiodide as Tool: A Personal Story

AbstractReview: [36 refs.

Indoloquinolines: Possible Biogenesis from Common Indole Precursors and their Synthesis using Domino Strategies

Indoloquinolines: Possible Biogenesis from Common Indole Precursors and their Synthesis using Domino Strategies

Indole-Producing Bacteria from the Biosynthetic Organs of a Muricid Mollusc Could Contribute to Tyrian Purple Production

ABSTRACT The muricid mollusc Dicathais orbita produces Tyrian purple, which is a brominated derivative of the blue dye indigo. This study aimed to establish whether distinct bacterial communities occur in the organs of D. orbita associated with Tyrian purple production and to identify indole-producing bacteria using 16S rRNA sequencing. Biochemical profiles of microbial communities from different D. orbita tissues were investigated and the composition of aerobic heterotrophic bacterial populations from homogenates and swabs assessed. There were significant differences in biochemical activity profiles and bacterial communities cultured from different D. orbita tissues, but no significant differences between males and females. Bacterial communities derived from foot tissue and seawater samples were similar. The biochemical and molecular evidence from swabs and tissue homogenates suggest indole-producing isolates are Vibrio spp. This study suggests Tyrian purple indole precursors could be obtained from oppor...

Strychnine as Target, Samarium Diiodide as Tool: A Personal Story.

Strychnine stands out from the group of classical natural products as one of the first complex compounds to be isolated in pure form and an extreme challenge to be structurally characterized. It has played a central role in natural product total syntheses and the surge in the development of innovative synthetic methods for many decades. Recently, we have accomplished one of the shortest formal total syntheses of strychnine (in ten steps and 14% overall yield or even shorter in eight steps and 10% overall yield). The evolution of a productive synthetic strategy, as well as the synthetic challenges tackled, are described here in detail, including examples of related transformations. The successful synthetic strategy was inspired by the premise that the core structure could be derived from simple aromatic indole precursors by a reductive SmI2 -induced ketyl-aryl coupling. Other key reactions included a diastereoselective reduction and a regioselective elimination protocol. Altogether one of the shortest syntheses of iso-strychnine and hence of strychnine was established.

Glycerol-Based Contrast Agents: A Novel Series of Dendronized Pentamethine Dyes

The synthesis of water-soluble dyes, which absorb and emit in the range between 650 and 950 nm and display high extinction coefficients (ε) as well as high fluorescence quantum yields (Φf), is still a demand for optical imaging. We now present a synthetic route for the preparation of a new group of glycerol-substituted cyanine dyes from dendronized indole precursors that have been functionalized as N-hydroxysuccinimide (NHS) esters. High Φf values of up to 0.15 and extinction coefficients of up to 189 000 L mol(-1) cm(-1) were obtained for the pure dyes. Furthermore, conjugates of the new dendronized dyes with the antibody cetuximab (ctx) that were directed against the epidermal growth factor receptor (EGFR) of tumor cells could be prepared with dye to protein ratios between 0.3 and 2.2 to assess their potential as imaging probes. For the first time, ctx conjugates could be achieved without showing a decrease in Φf and with an increasing labeling degree that exceeded the value of the pure dye even at a labeling degree above 2. The incorporation of hydrophilically and sterically demanding dendrimers into cyanines prevented dimer formation after covalent conjugation to the antibody. The binding functionality of the resulting ctx conjugates to the EGFR was successfully demonstrated by cell microscopy studies using EGFR expressing cell lines. In summary, the combination of hydrophilic glycerol dendrons with reactive dye labels has been established for the first time and is a promising approach toward more powerful fluorescent labels with less dimerization.

Crystal structure of (4R,5S)-4-methyl-3-methyl-sulfinyl-5-phenyl-1,3-oxazolidin-2-one.

The absolute structure of the chiral asymmetric indole precursor title compound, C11H13NO3S, was confirmed by refinement of the Flack and Hooft parameters and is that expected based on the starting materials for the synthesis. The phenyl group subtends a dihedral angle of 56.40 (5)° with the mean plane of the oxazolidinone ring, which adopts an envelope conformation, with the C atom bearing the methyl group as the flap. In the crystal, no significant directional inter­actions beyond van der Waals contacts are observed.

Studies on the glyphosate-induced amino acid starvation and addition of precursors on caffeic acid accumulation and profiles in adventitious roots of Echinacea purpurea (L.) Moench

Shikimate pathway leads to the production of several secondary metabolites including caffeic acid derivatives (CADs), phenols and flavonoids and its regulation is assumed to respond to the requirements for both the synthesis of protein and secondary metabolites. We tested the response of growth, accumulation of phenols, flavonoids, caffeic acid, CADs profiles and activities of shikimate dehydrogenase (SKDH; EC. 1.1.1.25), chorismate mutase (CM; EC. 5.4.99.5), phenylalanine ammonia lyase (PAL; EC. 4.3.1.5) to glyphosate-induced starvation and feeding of aromatic amino acids (l-phenylalanine and l-tryptophan) in adventitious root cultures of Echinacea purpurea. Feeding of l-phenylalanine enhanced the growth but the accumulation of phenols, flavanoids and caffeic acid was lower in comparison to the l-tryptophan fed cultures. The addition of l-tryptophan (0.5, 1 and 5 mM) resulted in an increase up to 56, 61, 84 % in phenol, 24, 12, 3 % in flavonoids and 86, 63, 39 % in total caffeic acid. When glyphosate was added, the growth and accumulation of secondary metabolites were suppressed massively. The addition of l-tryptophan to the media not only countered the deleterious impact of glyphosate but enhanced the growth and accumulation of secondary metabolites in root cultures. The activity of SKDH, CM and PAL induced in presence of l-tryptophan. However, l-phenylalanine addition resulted in increase and decrease of PAL and CM activity, respectively. The presence of glyphosate maximally induced the PAL activity but that could not be translated into higher accumulation of secondary metabolites as it suppresses the accumulation of its substrates i.e. aromatic amino acids. Among CADs, highest cichoric acid and chlorogenic acid was found in l-tryptophan (0.5 mM) which was 2.0 and 1.62 times more than the control treatments. We concluded that addition of l-tryptophan (indolic pathway precursor) and not the l-phenylalanine (phenylpropanoid pathway precursor) stimulate the growth and accumulation of secondary metabolites in adventitious root cultures of E. purpurea (L.) Moench.

ChemInform Abstract: Synthesis of C‐2 Arylated Tryptophan Amino Acids and Related Compounds Through Palladium‐Catalyzed C—H Activation.

AbstractThis simple, mild, and versatile method allows the preparation of α‐arylated indoles including amino acid derivatives directly from the corresponding indole or amino acid precursors.

ChemInform Abstract: Straightforward Protocol for the Efficient Synthesis of Varied N1‐Acylated (Aza) Indole 2‐/3‐Alkanoic Acids and Esters: Optimization and Scale‐up.

AbstractThe indole precursors for the acylation reaction are synthesized by esterification of commercially available indole substrates or by Fischer indole synthesis.

Concise total syntheses of (±)-noruleine and (±)-uleine

The first total synthesis of (±)-noruleine and a concise synthesis of (±)-uleine have been accomplished via the DDQ mediated dehydrogenative cyclization of a tetrahydrocarbazole derivative bearing a non-substituted amide functionality to prepare the key azocino[4,3-b]indole precursor.

Study of N1-alkylation of indoles from the reaction of 2(or 3)-aminoindole-3-(or 2)carbonitriles with DMF-dialkylacetals

The condensation of 2-aminoindole-3-carbonitriles and their 3-aminoindole-2-carbonitrile isomers with various DMF-dialkoxyacetals was investigated under microwaves. The appearance of reactive and versatile alkoxyiminium species allowed convenient access to indole precursors of building blocks with potential biological activity. The experimental results have been rationalised using DFT calculations of theoretical descriptors based on the electrostatic potential.