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Journal articles on the topic 'Synthesis of C1 to C21 region'

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Published: 4 June 2021

Last updated: 4 February 2022

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1

Paterson, Ian, Edward A. Anderson, Stephen M. Dalby, et al. "Progress toward a total synthesis of spirastrellolide A." Pure and Applied Chemistry 79, no. 4 (2007): 667–76. http://dx.doi.org/10.1351/pac200779040667.

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Progress toward a total synthesis of spirastrellolide A, a 38-membered marine macrolide, is reported. Syntheses of two diastereomers of the C1-C25 region, and an evolving Sharpless dihydroxylation strategy toward a C26-C40 fragment, are described. The syntheses exploit boron-mediated aldol chemistry to install key stereocenters, and feature late-stage thermodynamically controlled spiroacetalizations.

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2

Han, Bing Yuan, Nelson Y. S. Lam, Callum I. MacGregor, Jonathan M. Goodman, and Ian Paterson. "A synthesis-enabled relative stereochemical assignment of the C1–C28 region of hemicalide." Chemical Communications 54, no. 26 (2018): 3247–50. http://dx.doi.org/10.1039/c8cc00933c.

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3

Paterson, Ian, Nicola M. Gardner, and Guy J. Naylor. "Total synthesis of novel dictyostatin analogs and hybrids as microtubule-stabilizing anticancer agents." Pure and Applied Chemistry 81, no. 2 (2009): 169–80. http://dx.doi.org/10.1351/pac-con-08-09-17.

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Structural modification of the dictyostatin macrolide template through adaptation of our total synthesis has led to the identification of a number of potent analogs of this novel microtubule-stabilizing agent. A common synthetic strategy was exploited, employing a (Z)-selective Still-Gennari olefination between various advanced C11-C26 aldehyde and C4-C10 (or C1-C10) β-ketophosphonate intermediates. In vitro evaluation of the growth inhibitory activity of these analogs against both Taxol-sensitive and -resistant human cancer cell lines has provided a foundation for structure-activity relationship (SAR) studies to help define the pharmacophore region.

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4

Roulland, Emmanuel. "Tiacumicin B: An Antibiotic of Prime Importance and a Natural Product with an Inspiring Complex Structure." Synthesis 50, no. 21 (2018): 4189–200. http://dx.doi.org/10.1055/s-0037-1609933.

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This short review aims at decrypting and analyzing the various strategies used for the synthesis of tiacumicin B. Natural products synthesis is a way for organic chemists to express inventiveness, intellectual dexterity, and elegance in strategy of synthesis. Some molecular structures are more inspiring than others; and if like tiacumicin B, the architectural challenge meets high biological and medicinal interest, the molecule can then attract the attention of many groups of synthetic chemists.1 Introduction2 The Strategic Challenges of this Total Synthesis3 Construction of the C1–C5 Region4 Construction of the C14–C19 Region5 Construction of the C5–C12 Region6 Construction of the C12–C15 Diene Motif7 Macrocyclization8 Synthesis of the Rhamnosyl Donor9 Synthesis of the Noviosyl Donor and Glycosylation10 The Recurrent Problems Caused by Protective Groups11 Conclusion

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5

Bhattacharjee, Ashoke, Omid Soltani, and Jef K. De Brabander. "Synthesis of the C1−C21 (C1‘-C21‘) Fragment of the Dimeric Polyketide Natural Product SCH 351448." Organic Letters 4, no. 4 (2002): 481–84. http://dx.doi.org/10.1021/ol016938u.

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6

Swanson, M. S., T. Y. Nakagawa, K. LeVan, and G. Dreyfuss. "Primary structure of human nuclear ribonucleoprotein particle C proteins: conservation of sequence and domain structures in heterogeneous nuclear RNA, mRNA, and pre-rRNA-binding proteins." Molecular and Cellular Biology 7, no. 5 (1987): 1731–39. http://dx.doi.org/10.1128/mcb.7.5.1731.

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In the eucaryotic nucleus, heterogeneous nuclear RNAs exist in a complex with a specific set of proteins to form heterogeneous nuclear ribonucleoprotein particles (hnRNPs). The C proteins, C1 and C2, are major constituents of hnRNPs and appear to play a role in RNA splicing as suggested by antibody inhibition and immunodepletion experiments. With the use of a previously described partial cDNA clone as a hybridization probe, full-length cDNAs for the human C proteins were isolated. All of the cDNAs isolated hybridized to two poly(A)+ RNAs of 1.9 and 1.4 kilobases (kb). DNA sequencing of a cDNA clone for the 1.9-kb mRNA (pHC12) revealed a single open reading frame of 290 amino acids coding for a protein of 31,931 daltons and two polyadenylation signals, AAUAAA, approximately 400 base pairs apart in the 3' untranslated region of the mRNA. DNA sequencing of a clone corresponding to the 1.4-kb mRNA (pHC5) indicated that the sequence of this mRNA is identical to that of the 1.9-kb mRNA up to the first polyadenylation signal which it uses. Both mRNAs therefore have the same coding capacity and are probably transcribed from a single gene. Translation in vitro of the 1.9-kb mRNA selected by hybridization with a 3'-end subfragment of pHC12 demonstrated that it by itself can direct the synthesis of both C1 and C2. The difference between the C1 and C2 proteins which results in their electrophoretic separation is not known, but most likely one of them is generated from the other posttranslationally. Since several hnRNP proteins appeared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis as multiple antigenically related polypeptides, this raises the possibility that some of these other groups of hnRNP proteins are also each produced from a single mRNA. The predicted amino acid sequence of the protein indicates that it is composed of two distinct domains: an amino terminus that contains what we have recently described as a RNP consensus sequence, which is the putative RNA-binding site, and a carboxy terminus that is very negatively charged, contains no aromatic amino acids or prolines, and contains a putative nucleoside triphosphate-binding fold, as well as a phosphorylation site for casein kinase type II. The RNP consensus sequence was also found in the yeast poly(A)-binding protein (PABP), the heterogeneous nuclear RNA-binding proteins A1 and A2, and the pre-rRNA binding protein C23. All of these proteins are also composed of at least two distinct domains: an amino terminus, which possesses one or more RNP consensus sequences, and a carboxy terminus, which is unique to each protein, being very acidic in the C proteins and rich in glycine in A1, and C23 and rich in proline in the poly(A)-binding protein. These findings suggest that the amino terminus of these proteins possesses a highly conserved RNA-binding domain, whereas the carboxy terminus contains a region essential to the unique function and interactions of each of the RNA-binding proteins.

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7

Swanson, M. S., T. Y. Nakagawa, K. LeVan, and G. Dreyfuss. "Primary structure of human nuclear ribonucleoprotein particle C proteins: conservation of sequence and domain structures in heterogeneous nuclear RNA, mRNA, and pre-rRNA-binding proteins." Molecular and Cellular Biology 7, no. 5 (1987): 1731–39. http://dx.doi.org/10.1128/mcb.7.5.1731-1739.1987.

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In the eucaryotic nucleus, heterogeneous nuclear RNAs exist in a complex with a specific set of proteins to form heterogeneous nuclear ribonucleoprotein particles (hnRNPs). The C proteins, C1 and C2, are major constituents of hnRNPs and appear to play a role in RNA splicing as suggested by antibody inhibition and immunodepletion experiments. With the use of a previously described partial cDNA clone as a hybridization probe, full-length cDNAs for the human C proteins were isolated. All of the cDNAs isolated hybridized to two poly(A)+ RNAs of 1.9 and 1.4 kilobases (kb). DNA sequencing of a cDNA clone for the 1.9-kb mRNA (pHC12) revealed a single open reading frame of 290 amino acids coding for a protein of 31,931 daltons and two polyadenylation signals, AAUAAA, approximately 400 base pairs apart in the 3' untranslated region of the mRNA. DNA sequencing of a clone corresponding to the 1.4-kb mRNA (pHC5) indicated that the sequence of this mRNA is identical to that of the 1.9-kb mRNA up to the first polyadenylation signal which it uses. Both mRNAs therefore have the same coding capacity and are probably transcribed from a single gene. Translation in vitro of the 1.9-kb mRNA selected by hybridization with a 3'-end subfragment of pHC12 demonstrated that it by itself can direct the synthesis of both C1 and C2. The difference between the C1 and C2 proteins which results in their electrophoretic separation is not known, but most likely one of them is generated from the other posttranslationally. Since several hnRNP proteins appeared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis as multiple antigenically related polypeptides, this raises the possibility that some of these other groups of hnRNP proteins are also each produced from a single mRNA. The predicted amino acid sequence of the protein indicates that it is composed of two distinct domains: an amino terminus that contains what we have recently described as a RNP consensus sequence, which is the putative RNA-binding site, and a carboxy terminus that is very negatively charged, contains no aromatic amino acids or prolines, and contains a putative nucleoside triphosphate-binding fold, as well as a phosphorylation site for casein kinase type II. The RNP consensus sequence was also found in the yeast poly(A)-binding protein (PABP), the heterogeneous nuclear RNA-binding proteins A1 and A2, and the pre-rRNA binding protein C23. All of these proteins are also composed of at least two distinct domains: an amino terminus, which possesses one or more RNP consensus sequences, and a carboxy terminus, which is unique to each protein, being very acidic in the C proteins and rich in glycine in A1, and C23 and rich in proline in the poly(A)-binding protein. These findings suggest that the amino terminus of these proteins possesses a highly conserved RNA-binding domain, whereas the carboxy terminus contains a region essential to the unique function and interactions of each of the RNA-binding proteins.

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8

Bhattacharjee, Ashoke, Omid Soltani, and Jef K. De Brabander. "ChemInform Abstract: Synthesis of the C1-C21 (C1′-C21′) Fragment of the Dimeric Polyketide Natural Product SCH 351448." ChemInform 33, no. 25 (2010): no. http://dx.doi.org/10.1002/chin.200225213.

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9

Nubbemeyer, Udo, Adile Duymaz, Jochen Körber, Carolin Hofmann, and Dorothea Gerlach. "Synthesis of Optically Active 15-epi-9,14-Methylene Lipoxin A4." Synthesis 50, no. 06 (2018): 1246–58. http://dx.doi.org/10.1055/s-0036-1591899.

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The synthesis of lipoxin A4 and B4 analogues (LXA4, LXB4) to gain access to stabilized inflammation resolving compounds is an important field of research. Starting from known structural requirements of the natural compounds displaying biological activity and a broad investigation of their rapid metabolism, various LXA4 derivatives have been developed and tested. Focusing on variation and stabilization of the conjugated E,E,Z,E C7–C14 tetraene moiety of natural LXA4, a methylene bridge introduced between C9 and C14 might suppress any Z/E isomerization of the C11–C12 olefin. Intending to enable at least known structure variations in connection with the C1–C7 and the C15–C20 fragments, a convergent total synthesis starting from a known cycloheptatriene is developed. The C1–C8 building blocks are generated via six-step ex-chiral pool sequences starting from 2-deoxy-d-ribose delivering two 5,6-dihydroxy carboxylic acid derivatives with C7 aldehyde functions. The synthesis of the C8–C21 building block starts from a known cycloheptatriene 1-carbonester (C8–C14, C21) and hexanoyl chloride (C15–C20). After Friedel–Crafts-type coupling, the defined configuration of the C15 OH group is introduced via enantioselective reduction of the ketone precursor. Following an additional four steps, an aryl sulfone C9–C21 building block is completed ready for a key Julia–Kocienski olefination with the C1–C7 compounds. Finally, removal of the protecting groups completes the synthesis of the target optically active 9,14-methylene LXA4 methyl ester.

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10

Gudipati, Venugopal, and Dennis P. Curran. "Synthesis of C1–C20 and C21–C40 fragments of tetrafibricin." Tetrahedron Letters 52, no. 17 (2011): 2254–57. http://dx.doi.org/10.1016/j.tetlet.2011.01.086.

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11

Toshima, Kazunobu, Tsuyoshi Arita, Koji Kato, Daisuke Tanaka, and Shuichi Matsumura. "Synthetic studies on apoptolidin: synthesis of the C1–C21 macrolide fragment." Tetrahedron Letters 42, no. 50 (2001): 8873–76. http://dx.doi.org/10.1016/s0040-4039(01)01948-7.

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12

Harris, Laurence, Krzysztof Jarowicki, Philip Kocienski, and Richard Bell. "Synthetic Approaches to Rapamycin. 3. Synthesis of a C1-C21 Fragment." Synlett 1996, no. 09 (1996): 903–5. http://dx.doi.org/10.1055/s-1996-5604.

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13

Zhang, Zhigao, Yue Ding, Jianyan Xu, Yong Chen, and Craig J. Forsyth. "Synthesis of the C1–C21 Domain of Azaspiracids-1 and −3." Organic Letters 15, no. 10 (2013): 2338–41. http://dx.doi.org/10.1021/ol400487e.

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14

Toshima, Kazunobu, Tsuyoshi Arita, Koji Kato, Daisuke Tanaka, and Shuichi Matsumura. "ChemInform Abstract: Synthetic Studies on Apoptolidin: Synthesis of the C1-C21 Macrolide Fragment." ChemInform 33, no. 10 (2010): no. http://dx.doi.org/10.1002/chin.200210213.

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15

Maurer, Karl W., and Robert W. Armstrong. "Synthesis of the C1−C21 Fragment of the Serine/Threonine Phosphatase Inhibitor Tautomycin." Journal of Organic Chemistry 61, no. 9 (1996): 3106–16. http://dx.doi.org/10.1021/jo952083l.

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16

Marshall, James A., and Mathew M. Yanik. "Synthesis of a C1−C21 Subunit of the Protein Phosphatase Inhibitor Tautomycin: A Formal Total Synthesis." Journal of Organic Chemistry 66, no. 4 (2001): 1373–79. http://dx.doi.org/10.1021/jo0056951.

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17

HARRIS, L., K. JAROWICKI, P. KOCIENSKI, and R. BELL. "ChemInform Abstract: Synthetic Approaches to Rapamycin. Part 3. Synthesis of a C1-C21 Fragment." ChemInform 28, no. 7 (2010): no. http://dx.doi.org/10.1002/chin.199707273.

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18

MAURER, K. W., and R. W. ARMSTRONG. "ChemInform Abstract: Synthesis of the C1-C21 Fragment of the Serine/Threonine Phosphatase Inhibitor Tautomycin." ChemInform 27, no. 36 (2010): no. http://dx.doi.org/10.1002/chin.199636248.

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19

Chakraborty, Tushar Kanti, and Bajjuri Krishna Mohan. "Studies directed towards the synthesis of antascomicin A: stereoselective synthesis of the C1–C21 fragment of the molecule." Tetrahedron Letters 47, no. 29 (2006): 4999–5002. http://dx.doi.org/10.1016/j.tetlet.2006.05.113.

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20

Kaliappan, Krishna, and Parthasarathy Gowrisankar. "Synthetic Studies on a Marine Natural Product, Palmerolide A: Synthesis of C1-C9 and C15-C21 Fragments." Synlett 2007, no. 10 (2007): 1537–40. http://dx.doi.org/10.1055/s-2007-982539.

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21

Carter, Rich G., and David J. Weldon. "Studies Directed toward the Total Synthesis of Azaspiracid: Stereoselective Construction of C1−C12, C13−C19, and C21−C25Fragments." Organic Letters 2, no. 24 (2000): 3913–16. http://dx.doi.org/10.1021/ol006674w.

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22

Soln, Josip. "Limiting Velocities of Primary, Obscure and Normal Particles: Self-Annihilating Obscure Particle as an Example of Dark Matter Particle." Applied Physics Research 8, no. 5 (2016): 1. http://dx.doi.org/10.5539/apr.v8n5p1.

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From recently established bicubic equation, three particle limiting velocities are derived, primary, c1,obscure, c2 and normal, c3,that in principle may belong to a single particle. The values of limiting velocities are governed by the congruent particle parameter, z = 3\sqrt3mv2=2E, with m; v and E being, respectively, particle mass, velocity and energy, generally satisfying 1 &lt;= z &lt;= 1, and here just 0 &lt;= z &lt;= 1.<br />While c3 is practically the same in value as v, c1 and c2 can depart from v as z changes from 1 to 0, since c1, c2 and c3; are, in forms, explicitly different from each other, which offers the chance to look at possible new forms of matter, such as dark matter. For instance, one finds that c3 could be slightly different from c, the velocity of light, for the 2010 Crab Nebula Flare PeV electron energy region and for the OPERA 17 GeV muon neutrino velocity experiments, while at the same time, although not measurable in these experiments, calculated c1 and jc2j, are numerically about 105 times larger than c3.<br />There is a belief that an exemplary particle of small velocity, v = 10-3c ,and small energy, E = 1eV , but as yet of not known mass, should belong to the dark matter class. Once knowing z the value of the mass is fixed with 3\sqrt3m(z)v2 = 2Ez ,and its maximum value m(1) is at z = 1, m(1) = 2E=(v23\sqrt3):This mass value defines the test particle, with which one calulates primary, obscure and normal particle rest energies at z = 1: Snce at z = 1 theory predicts c21(1) = (3=2) v2;c22<br />(1) = 3v2; c23 (1) = (3=2) v2, the rest energies are m(1) c21(1) = m(1) c23(1) = 0:58eV and m(1)(c22(1))= 1:15eV. The primary and normal particles, with positive kinetic energies self-creation process increase their energies from 0:58eV to desired1eV: The obscure particle, with negative kinetic energy self-annihilation process decreases its energy of 1:15eV to desired 1eV. This makes the obscure (imaginary c2) particle as a good candidate for a dark matter particle,since as it is believed that a trapped dark matter particle with self-annihilation properties helps keeping the equilibrium between capture and annihilation rates in the sun.

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23

Frampton, Christopher S., James H. Gall, and David D. MacNicol. "Novel Ansa-Chain Conformation of a Semi-Synthetic Rifamycin Prepared Employing the Alder-Ene Reaction: Crystal Structure and Absolute Stereochemistry." Chemistry 3, no. 3 (2021): 734–43. http://dx.doi.org/10.3390/chemistry3030052.

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Rifamycins are an extremely important class of antibacterial agents whose action results from the inhibition of DNA-dependent RNA synthesis. A special arrangement of unsubstituted hydroxy groups at C21 and C23, with oxygen atoms at C1 and C8 is essential for activity. Moreover, it is known that the antibacterial action of rifamycin is lost if either of the two former hydroxy groups undergo substitution and are no longer free to act in enzyme inhibition. In the present work, we describe the successful use of an Alder-Ene reaction between Rifamycin O, 1 and diethyl azodicarboxylate, yielding 2, which was a targeted introduction of a relatively bulky group close to C21 to protect its hydroxy group. Many related azo diesters were found to react analogously, giving one predominant product in each case. To determine unambiguously the stereochemistry of the Alder-Ene addition process, a crystalline zwitterionic derivative 3 of the diethyl azodicarboxylate adduct 2 was prepared by reductive amination at its spirocyclic centre C4. The adduct, as a mono chloroform solvate, crystallized in the non-centrosymmetric Sohnke orthorhombic space group, P212121. The unique conformation and absolute stereochemistry of 3 revealed through X-ray crystal structure analysis is described.

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24

Chakraborty, Tushar Kanti, Rajib Kumar Goswami, and Midde Sreekanth. "Studies directed towards the total synthesis of lycoperdinosides: stereoselective construction of the C1–C9 and C10–C21 segments of the molecules." Tetrahedron Letters 48, no. 23 (2007): 4075–78. http://dx.doi.org/10.1016/j.tetlet.2007.04.016.

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25

Carter, Rich G., and David J. Weldon. "ChemInform Abstract: Studies Directed Toward the Total Synthesis of Azaspiracid: Stereoselective Construction of C1-C12, C13-C19, and C21-C25 Fragments." ChemInform 32, no. 15 (2001): no. http://dx.doi.org/10.1002/chin.200115238.

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26

Lee, Hyo Won, Yong Deog Hong, and Ihl-Young Choi Lee. "ChemInform Abstract: Synthesis Toward Epothilone A: Coupling Reaction Between the Sulfone of C1-C10 and the Allylic Bromide of C11-C21." ChemInform 30, no. 41 (2010): no. http://dx.doi.org/10.1002/chin.199941263.

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27

Prasad, Kavirayani, and Amit Pawar. "Stereoselective Synthesis of C1-C18 Region of Palmerolide A from Tartaric Acid." Synlett 2010, no. 07 (2010): 1093–95. http://dx.doi.org/10.1055/s-0029-1219797.

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28

Nicolaou, K. C., David Y. K. Chen, Yiwei Li, et al. "Total Synthesis of the Proposed Azaspiracid-1 Structure, Part 2: Coupling of the C1–C20, C21–C27, and C28–C40 Fragments and Completion of the Synthesis." Angewandte Chemie 115, no. 31 (2003): 3777–81. http://dx.doi.org/10.1002/ange.200351826.

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29

Nicolaou, K. C., David Y. K. Chen, Yiwei Li, et al. "Total Synthesis of the Proposed Azaspiracid-1 Structure, Part 2: Coupling of the C1–C20, C21–C27, and C28–C40 Fragments and Completion of the Synthesis." Angewandte Chemie International Edition 42, no. 31 (2003): 3649–53. http://dx.doi.org/10.1002/anie.200351826.

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30

Nicolaou, K. C., Yiwei Li, Noriaki Uesaka, et al. "Total Synthesis of the Proposed Azaspiracid-1 Structure, Part 1: Construction of the Enantiomerically Pure C1–C20, C21–C27, and C28–C40 Fragments." Angewandte Chemie 115, no. 31 (2003): 3771–76. http://dx.doi.org/10.1002/ange.200351825.

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31

Nicolaou, K. C., Yiwei Li, Noriaki Uesaka, et al. "Total Synthesis of the Proposed Azaspiracid-1 Structure, Part 1: Construction of the Enantiomerically Pure C1–C20, C21–C27, and C28–C40 Fragments." Angewandte Chemie International Edition 42, no. 31 (2003): 3643–48. http://dx.doi.org/10.1002/anie.200351825.

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32

Cooper, Arthur J., Wenxi Pan, and Robert G. Salomon. "Total synthesis of halichondrin b from common sugars: An F-ring intermediate from D-glucose and efficient construction of the C1 to C21 segment." Tetrahedron Letters 34, no. 51 (1993): 8193–96. http://dx.doi.org/10.1016/s0040-4039(00)61388-6.

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33

Babu, Srinivasarao Arulananda, and Arup Dalal. "Pd(II)-Catalyzed Directing-Group-Aided C–H Arylation and Alkylation of Pyrene Core: Synthesis of C1,C2- and C1,C10-Disubstituted Pyrene Motifs." Synthesis 53, no. 18 (2021): 3307–24. http://dx.doi.org/10.1055/a-1472-0881.

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AbstractWe report the application of the Pd(II)-catalyzed, directing-group-aided C–H arylation/alkylation tactics to functionalize the pyrene core, especially, the relatively inaccessible C2 and K-region C10 positions of the pyrene core and augmentation of the library of pyrene derivatives with C1,C2- and C1,C10-disubstituted pyrene motifs. The Pd(II)-catalyzed β-C–H arylation/alkylation of the C2-position of pyrene-1-carboxamide possessing an 8-aminoquinoline directing group yielded various C1,C2-disubstituted pyrenes. Similarly, the Pd(II)-catalyzed selective γ-C–H arylation/alkylation of the C10-position of N-(pyren-1-yl)picolinamide, possessing a picolinamide directing group, yielded various C1,C10-disubstituted pyrenes. Examples of C(9)–H arylation of pyrene-1-carboxamide and the removal of the directing group after the C–H arylation/alkylation reactions were also shown. The structures of representative pyrene derivatives were confirmed by the X-ray structure analysis. Given the importance of the pyrene derivatives in various fields of chemical sciences, this report is a contribution towards augmentation of the library of pyrene derivatives with C1,C2- and C1,C10-disubstituted pyrene amide motifs.

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34

Garcin, Dominique, Jean-Baptiste Marq, Fréderic Iseni, Stephen Martin, and Daniel Kolakofsky. "A Short Peptide at the Amino Terminus of the Sendai Virus C Protein Acts as an Independent Element That Induces STAT1 Instability." Journal of Virology 78, no. 16 (2004): 8799–811. http://dx.doi.org/10.1128/jvi.78.16.8799-8811.2004.

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ABSTRACT The Sendai virus C protein acts to dismantle the interferon-induced cellular antiviral state in an MG132-sensitive manner, in part by inducing STAT1 instability. This activity of C maps to the first 23 amino acids (C1-23) of the 204-amino-acid (aa)-long protein (C1-204). C1-23 was found to act as an independent viral element that induces STAT1 instability, since this peptide fused to green fluorescent protein (C1-23/GFP) is at least as active as C1-204 in this respect. This peptide also induces the degradation of C1-23/GFP and other proteins to which it is fused. Most of C1-204, and particularly its amino-terminal half, is predicted to be structurally disordered. C1-23 as a peptide was found to be disordered by circular dichroism, and the first 11 aa have a strong potential to form an amphipathic α-helix in low concentrations of trifluoroethanol, which is thought to mimic protein-protein interaction. The critical degradation-determining sequence of C1-23 was mapped by mutation to eight residues near its N terminus: 4FLKKILKL11. All the large hydrophobic residues of 4FLKKILKL11, plus its ability to form an amphipathic α-helix, were found to be critical for STAT1 degradation. In contrast, C1-23/GFP self-degradation did not require 8ILKL11, nor the ability to form an α-helix throughout this region. Remarkably, C1-23/GFP also stimulated C1-204 degradation, and this degradation in trans required the same peptide determinants as for STAT1. Our results suggest that C1-204 coordinates its dual activities of regulating viral RNA synthesis and counteracting the host innate antiviral response by sensing both its own intracellular concentration and that of STAT1.

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35

Dudley, Gregory, and David Jones. "Synthesis of the C1-C15 Region of Palmerolide A Using Refined Claisen-Type Addition-Bond Cleavage Methodology." Synlett 2010, no. 02 (2009): 223–26. http://dx.doi.org/10.1055/s-0029-1218565.

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36

McDonald, Frank E., and Colleen C. Schultz. "Sequential application of stereoselective syn-oxidation methodologies to natural product synthesis: A potentially biomimetic approach to the C12–C21 bistetrahydrofuran region of monensin." Tetrahedron 53, no. 48 (1997): 16435–48. http://dx.doi.org/10.1016/s0040-4020(97)01026-0.

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37

Cordeiro, Suellem, Leticia Pereira, Marina de O. Simoes, and Maria de Fatima Marques. "Synthesis and Evaluation of New Bis(imino) Pyridine Based Catalysts for Ethylene Polymerization." Chemistry & Chemical Technology 10, no. 4 (2016): 413–21. http://dx.doi.org/10.23939/chcht10.04.413.

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Three-component catalytic systems based on 2,6-bis(imino) pyridine iron(II) chloride were synthesized from different ligands, which provided new alternative catalysts for polymerization of ethylene. The synthesized catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), and the lack of absorption bands was observed in the region related to the carbonyl, as well as the presence of bands in the region of imino groups corresponding to C=N bonds. Coordination with Fe was also carried out. The structure of the ligands and the new catalysts were confirmed by the elemental analysis (CHN), and 1H- and 13C-nuclear magnetic resonance spectroscopy. In ethylene polymerization with methylaluminoxane as a cocatalyst, the activity of catalyst C1 was high. Although this catalyst structure contains sterically bulky ligands, the metal center was not sufficiently protected allowing transfer reactions, producing polyethylene with a low molar mass and melting temperature.

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MCDONALD, F. E., and C. C. SCHULTZ. "ChemInform Abstract: Sequential Application of Stereoselective syn-Oxidation Methodologies to Natural Product Synthesis: A Potentially Biomimetic Approach to the C12-C21 Bistetrahydrofuran Region of Monensin." ChemInform 29, no. 11 (2010): no. http://dx.doi.org/10.1002/chin.199811265.

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L. Calandrino, Rosemarie, Katherine J. McAuliffe, Lauren E. Dolmage, and Evan R. Trivedi. "Synthesis of the C3 and C1 Constitutional Isomers of Trifluorosubphthalocyanine and Their Fluorescence within MDA-MB-231 Breast Tumor Cells." Molecules 24, no. 21 (2019): 3832. http://dx.doi.org/10.3390/molecules24213832.

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Metal tetrapyrrole macrocycles such as porphyrins and chlorins are ubiquitous in nature. Synthetic analogs, including phthalocyanines, have found applications in medicine, particularly as photosensitizers for photodynamic therapy and as fluorescent imaging probes. Tripyrrolic macrocycles, called subphthalocyanines (SPcs) with a smaller boron atom at their core, have similar potential as optical agents. We have recently reported a series of mixed fluorinated SPcs with varying aromaticity, showing that electronic absorption and emission are synthetically tunable across the far visible region, and that the inclusion of 4–12 peripheral fluorine atoms results in strong fluorescence within MDA-MB-231 breast tumor cells. Further probing this system, we report herein the synthesis and characterization of boron trifluorosubphthalocyanine chloride (F3SPc). The constitutional isomers F3SPc(C3) and F3SPc(C1) are readily separable by chromatography, and their identity and purity have been confirmed by 1H NMR, 19F NMR, HR APCI-MS, and HPLC. Unsurprisingly, these structurally similar F3SPcs have identical electronic absorption (λmax = 557 nm; tetrahydrofuran (THF)) and emission (λem = 574 nm; Φf = 0.27–0.28; THF). Strong fluorescence from MDA-MB-231 breast tumor cells was observed following treatment with F3SPc(C3) and F3SPc(C1) (50 µM F3SPc, 15 min), further highlighting the importance of even a limited number of peripheral fluorine atoms for this type of application.

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Marin, Victor, Andres Iturra, Andres Opazo, et al. "Oxidation of Isodrimeninol with PCC Yields Drimane Derivatives with Activity against Candida Yeast by Inhibition of Lanosterol 14-Alpha Demethylase." Biomolecules 10, no. 8 (2020): 1101. http://dx.doi.org/10.3390/biom10081101.

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Candida species cause an opportunistic yeast infection called Candidiasis, which is responsible for more than 50,000 deaths every year around the world. Effective treatments against candidiasis caused by non-albicans Candida species such as C. glabrata, C. parapsilosis, C. aureus, and C. krusei are limited due to severe resistance to conventional antifungal drugs. Natural drimane sesquiterpenoids have shown promising antifungal properties against Candida yeast and have emerged as valuable candidates for developing new candidiasis therapies. In this work, we isolated isodrimeninol (C1) from barks of Drimys winteri and used it as starting material for the hemi-synthesis of four sesquiterpenoids by oxidation with pyridinium chlorochromate (PCC). The structure of the products (C2, C3, C4, and C5) was elucidated by 1D and 2D NMR spectroscopy resulting in C4 being a novel compound. Antifungal activity assays against C. albicans, C. glabrata, and C. krusei revealed that C4 exhibited an increased activity (IC50 of 75 μg/mL) compared to C1 (IC50 of 125 μg/mL) in all yeast strains. The antifungal activity of C1 and C4 was rationalized in terms of their capability to inhibit lanosterol 14-alpha demethylase using molecular docking, molecular dynamics simulations, and MM/GBSA binding free energy calculations. In silico analysis revealed that C1 and C4 bind to the outermost region of the catalytic site of 14-alpha demethylase and block the entrance of lanosterol (LAN) to the catalytic pocket. Binding free energy estimates suggested that C4 forms a more stable complex with the enzyme than C1, in agreement with the experimental evidence. Based on this new approach it is possible to design new drimane-type sesquiterpenoids for the control of Candida species as inhibitors of 14-alpha demethylase.

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Liao, Qiang Qiang, Yi Jiu Li, and Bo Xiang. "Synthesis and Characterization of an Aminated D-Glucose and its Stability of Cu²⁺Complex." Advanced Materials Research 197-198 (February 2011): 65–68. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.65.

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An aminated D-glucose [N,N'-di-b-D-glucopyranosyl ethylenediamine] was prepared and thoroughly characterized by FT-IR, ESI-MS, NMR spectra and elemental analysis. Compared with D-glucose, the FT-IR spectrum of the aminated glucose showed a moderate peak at 1629~1608 cm-1which was attributed to dNH vibration, suggesting glucose reacted to ethylenediamine (en). The ESI-MS spectrum exhibited a strong peak atm/z383.2, which was assigned to the species [C14H27O10N2]-. The1H-NMR spectrum of the aminated D-glucose demonstrated the signal of the C1proton and the amino proton at 4.82~4.79ppm, illustrating the amino of ethylenediamine was substituted for the hydroxy group of C1. As for UV spectra, the aminated glucose hadn’t absorbance in the ultraviolet region while its complex with Cu2+had obvious absorption peak at about 236nm. The complex ratio of the aminated glucose to Cu2+was close to 1:1 and the stability constant of its Cu2+complex was 6.8*107in 0.01mol×L-1borax buffer solution.

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Huamani-Palomino, Ronny G., Bryan M. Córdova, Elvis Renzo Pichilingue L., Tiago Venâncio, and Ana C. Valderrama. "Functionalization of an Alginate-Based Material by Oxidation and Reductive Amination." Polymers 13, no. 2 (2021): 255. http://dx.doi.org/10.3390/polym13020255.

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This research focused on the synthesis of a functional alginate-based material via chemical modification processes with two steps: oxidation and reductive amination. In previous alginate functionalization with a target molecule such as cysteine, the starting material was purified and characterized by UV-Vis, 1H-NMR and HSQC. Additionally, the application of FT-IR techniques during each step of alginate functionalization was very useful, since new bands and spiked signals around the pyranose ring (1200–1000 cm−1) and anomeric region (1000–750 cm−1) region were identified by a second derivative. Additionally, the presence of C1-H1 of β-D-mannuronic acid residue as well as C1-H1 of α-L-guluronic acid residue was observed in the FT-IR spectra, including a band at 858 cm−1 with characteristics of the N-H moiety from cysteine. The possibility of attaching cysteine molecules to an alginate backbone by oxidation and post-reductive amination processes was confirmed through 13C-NMR in solid state; a new peak at 99.2 ppm was observed, owing to a hemiacetal group formed in oxidation alginate. Further, the peak at 31.2 ppm demonstrates the presence of carbon -CH2-SH in functionalized alginate—clear evidence that cysteine was successfully attached to the alginate backbone, with 185 μmol of thiol groups per gram polymer estimated in alginate-based material by UV-Visible. Finally, it was observed that guluronic acid residue of alginate are preferentially more affected than mannuronic acid residue in the functionalization.

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Schoonen, W. G. E. J., J. G. D. Lambert, J. W. Resink, W. J. A. R. Viveen, and P. G. W. J. Van Oordt. "A quantitative study of steroid bioconversions in the testis of the African catfish, Clarias gariepinus (Burchell), under natural spawning and natural and cultivated non-spawning conditions." Journal of Endocrinology 112, no. 2 (1987): 323–32. http://dx.doi.org/10.1677/joe.0.1120323.

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ABSTRACT Quantitative aspects of bioconversions in the testes of the African catfish (Clarias gariepinus) were studied in vitro by incubation of tissue with [3H]pregnenolone or [3H]androstenedione. During the breeding period, spawning and non-spawning animals were collected from their natural habitat, the Hula nature reserve, in northern Israel. In the same period, non-spawning animals were collected from a fish pond in the same region. It was shown that spawning was accompanied by significant changes in steroid bioconversions, i.e. a reduction in androgen synthesis, especially of 11β-hydroxyandrostenedione and 11β-hydroxytestosterone and an increase in the production of C21-steroids, especially progesterone, 17α-hydroxyprogesterone and a pregnenolone ester. These changes resulted from a decreased contribution of the cytochrome P-450 enzymes 17α-hydroxylase, C17–20-lyase and 11β-hydroxylase. A rise in plasma gonadotrophin concentration was observed only in spawning catfish. In the absence of such an increase in plasma gonadotrophin, steroid synthesis in the testes of non-spawning feral and pond catfish was primarily directed towards the production of 11-oxygenated androgens and 5β-pregnane-3α,17α,20α-triol. It is suggested that spawning is induced by gonadotrophin and the ensuing change in steroidogenesis. It is possible that husbandry conditions inhibit the necessary increase in gonadotrophin release. J. Endocr. (1987) 112, 323–332

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Liu, Yanyong. "Hydrocracking of Polyethylene to Jet Fuel Range Hydrocarbons over Bifunctional Catalysts Containing Pt- and Al-Modified MCM-48." Reactions 1, no. 2 (2020): 195–209. http://dx.doi.org/10.3390/reactions1020014.

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A low-density polyethylene was hydrocracked to liquid hydrocarbons in autoclave reactors over catalysts containing Pt- and Al-modified MCM-48. Two kinds of Al-modified MCM-48 were synthesized for the reaction: Al-MCM-48 was synthesized using a sol–gel method by mixing Al(iso-OC3H7)3 with Si(OC2H5)4 and surfactant in a basic aqueous solution before hydrothermal synthesis, and Al/MCM-48 was synthesized using a post-modification method by grafting Al3+ ions on the surface of calcined Al/MCM-48. X-ray diffraction (XRD) patterns indicated that both Al-MCM-48 and Al/MCM-48 had a cubic mesoporous structure. The Brunauer–Emmett–Teller (BET) surface areas of Al-MCM-48 and Al/MCM-48 were larger than 1000 m2/g. 27Al Magic Angle Spinning-NMR (MAS NMR) indicated that Al3+ in Al-MCM-48 was located inside the framework of mesoporous silica, but Al3+ in Al/MCM-48 was located outside the framework of mesoporous silica. The results of ammonia temperature-programmed desorption (NH3-TPD) showed that the acidic strength of various samples was in the order of H-Y > Al/MCM-48 > Al-MCM-48 > MCM-48. After 4 MPa H2 was charged in the autoclave at room temperature, 1 wt % Pt/Al/MCM-48 catalyst showed a high yield of C9−C15 jet fuel range hydrocarbons of 85.9% in the hydrocracking of polyethylene at 573 K for 4 h. Compared with the reaction results of Pt/Al/MCM-48, the yield of light hydrocarbons (C1−C8) increased over Pt/H-Y, and the yield of heavy hydrocarbons (C16−C21) increased over Pt/Al-MCM-48 in the hydrocracking of polyethylene. The yield of C9−C15 jet fuel range hydrocarbons over the used catalyst did not decrease compared to the fresh catalyst in the hydrocracking of polyethylene to jet fuel range hydrocarbons over Pt/Al/MCM-48.

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Hu, Jiang, Bingang Shi, Jianpeng Xie, et al. "Tissue Expression and Variation of the DGAT2 Gene and Its Effect on Carcass and Meat Quality Traits in Yak." Animals 9, no. 2 (2019): 61. http://dx.doi.org/10.3390/ani9020061.

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Diacylglycerol acyltransferase-2 (DGAT2) plays a key role in the synthesis of animal triglycerides (TGs). This study investigated the relative expression of the DGAT2 gene in tissues, variation in the gene, and its association with carcass and meat quality traits in yaks (Bos grunniens). DGAT2 was found to be expressed in twelve tissues investigated, but the highest expression was detected in subcutaneous fat, and moderate levels were observed in the liver, heart, longissimus dorsi muscle, and abomasum. Three variants (A1 to C1) were found in intron 5 and another three variants (A2 to C2) were found in intron 6, with two single-nucleotide polymorphisms (SNPs) being identified in each region in 694 Gannan yaks. Variants B1 and C2 were associated with a decrease in Warner–Bratzler shear force (WBSF) (p = 0.0020 and p = 0.0441, respectively), and variant C1 was associated with an increase in WBSF (p = 0.0434) and a decrease in drip loss rate (p = 0.0271), whereas variant B2 was associated with a decrease in cooking loss rate (p = 0.0142). Haplotypes A1-A2 and B1-A2 were found to be, respectively, associated with an increase and a decrease in WBSF (p = 0.0191 and p = 0.0010, respectively). These results indicate that DGAT2 could be a useful gene marker for improving meat tenderness in yaks.

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Kobayashi, Shoko. "The Effect of Polyphenols on Hypercholesterolemia through Inhibiting the Transport and Expression of Niemann–Pick C1-Like 1." International Journal of Molecular Sciences 20, no. 19 (2019): 4939. http://dx.doi.org/10.3390/ijms20194939.

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The Niemann–Pick C1-like 1 (NPC1L1) protein is a cholesterol transporter that is expressed in the small intestine. This report describes the discovery of NPC1L1, its transport properties, and the inhibitory effects of polyphenols on NPC1L1. NPC1L1 was identified in 2004 while searching for ezetimibe molecular targets. Excessive synthesis of cholesterol results in hyperlipidemia, which increases the amount of bile cholesterol excreted into the duodenum. The inhibition of NPC1L1 decreases blood cholesterol because food and bile cholesterol are also absorbed from NPC1L1 in the intestine. Some polyphenols, particularly luteolin, have been reported as NPC1L1-mediated anti-dyslipidemia constituents. Luteolin affects NPC1L1 through two mechanisms. Luteolin directly inhibits NPC1L1 by binding to it, which occurs in a short timeframe similar to that for ezetimibe. The other mechanism is the inhibition of NPC1L1 expression. Luteolin reduced the binding of Sterol-regulatory element-binding protein 2 (SREBP2) in the promoter region of the NPC1L1 gene and decreased mRNA levels of SREBP2 and hepatocyte nuclear factor 4α. These data suggest that luteolin decreases the expression of NPC1L1 through regulation of transcription factors. This review also explores the effect of other polyphenols on NPC1L1 and hypercholesterolemia.

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Zhang, Jing, Xiaoma Tao, Gemei Cai, and Zhanpeng Jin. "Phase relation, structure, and properties of borate MgYB5O10 in MgO–Y2O3–B2O3 system." Powder Diffraction 32, no. 2 (2017): 97–106. http://dx.doi.org/10.1017/s0885715617000227.

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In the investigation of MgO–Y2O3–B2O3 system, six three-phase regions, five binary compounds, and one ternary compound MgYB5O10 were confirmed in the subsolidus phase relations. Single-phase powder sample of MgYB5O10 was successfully prepared through solution synthesis method. By using the Rietveld method from the step-scanning X-ray powder diffraction data, the crystal structure of MgYB5O10 was determined. It crystallizes in the monoclinic system with the space group P121/c1 and lattice parameters a = 8.5113(2) Å, b = 7.5892(2) Å, c = 12.2460(3) Å, β = 130.200(1)°, and Z = 4. The infrared spectrum of MgYB5O10 at room temperature demonstrates the existence of BO3 and BO4 groups. The UV–visible spectrum shows a wide absorption band within the range of 190–400 nm, while the absorption in the visible region is negligible. According to the electronic structure derived by first-principles calculations, MgYB5O10 is an insulator with a wide indirect energy band gap of about 5.95 eV. Layered structural characteristics, existence of one-dimensional YnO8n+2 chains, and the large band gap should be the immanent reason why MgYB5O10-based materials have exhibited outstanding performances in the luminescence field.

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Škvor Jernejčič, Brina. "The Earliest Cremation Burials in the South-Eastern Alpine Region from the Middle Bronze Age – Signs of Intercultural Connections with the Northern Carpathian Basin." Praehistorische Zeitschrift 95, no. 2 (2020): 447–90. http://dx.doi.org/10.1515/pz-2020-0024.

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AbstractThe article considers cremation graves from the site of Podsmreka near Višnja Gora (Slovenia). Based on the analysis of their pottery, it could be shown that the graves can be dated to the Middle Bronze Age period (Br B2/C1) and thus represent one of the oldest cremation burials of the Bronze Age in Slovenia. First, the ceramic finds from the radiocarbon dated settlement contexts are discussed in order to reach a more exact chronological framework for the vessel forms from graves. A synthesis of all Middle Bronze Age graves, both inhumations and cremations, from central and eastern Slovenia allows us to get a better understanding of when the change in burial practices occurred. Surprisingly, the best analogies for the vessels from graves at Podsmreka near Višnja Gora can be found in the northern Carpathian Basin, where we observe a long-standing tradition of cremation burials. The analysis of radiocarbon samples from two graves from Šafárikovo in Slovakia allowed us to verify the absolute chronology of urn amphorae vessels with particular form and decoration, which we can date between the second half of the 16th and the first half of the 15th century BC. Such astonishing correspondences in the pottery between the northern Carpathian Basin and the south-eastern Alpine region seem to indicate that the very area of the Upper Tisza river, and the territory of the Piliny Culture, played a crucial role in the transmission of new burial practices, not only to Slovenia, but also across wider areas along the Sava and Drava rivers on the distribution area of the Virovitica group.

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Trippe, Lukas, Analuisa Nava, Andrea Frank, Dieter Schollmeyer та Udo Nubbemeyer. "Synthesis of Enantiopure ω-(4-Fluorophenyl) 6,11-Methylene Lipoxin B4 Methyl Ester". Synthesis, 19 травня 2021. http://dx.doi.org/10.1055/a-1512-1763.

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The synthesis of Lipoxin B4 analogs (LXB4) to gain access to stabilized inflammation resolving compounds is an active field of research. Focusing on variation and stabilization of the conjugated E,Z,E,E C6–C13 tetraene moiety of natural LXB4, a methylene bridge introduced between C6 and C11 suppresses any Z/E isomerization of the C8–C9 olefin. Furthermore, rapid ω-oxidation (C20) should be avoided by replacing the C18-C20 segment by an aromatic moiety. Optically active C1–C12 building blocks were accessed from cycloheptatriene 1-carbonester (C6–C11, C21) and glutaryl chloride (C1–C5) as described earlier. The ω-segment had been generated via a five-step sequence starting from 4-arylbutanoic acid. Horner key olefination enabled assembly of the carbon backbone. A final five step sequence including a chelate Cram reduction of the unsaturated ketone moiety afforded the target ω-aryl 6,11-methylene-LXB4 methyl ester.

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Paterson, Ian, Edward A. Anderson, and Stephen M. Dalby. "Synthesis of the C1—C21 Southern Hemisphere of the Originally Proposed Structure of Spirastrellolide A." ChemInform 37, no. 18 (2006). http://dx.doi.org/10.1002/chin.200618217.

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