Natural products in the predatory defence of the filamentous fungal pathogen Aspergillus fumigatus

Jana M. Boysen,
Nauman Saeed and
Falk Hillmann

Review
Published 28 Jul 2021

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1. Graphical Abstract
2. Figure 1: Schematic overview of fungal interactions in the environment. Fungi can be found in essentially all...
  
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3. Figure 2: Fungal derived bioactive natural compounds with ecological and/or economic relevance.
  
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4. Figure 3: Gliotoxin biosynthetic gene cluster and it major biosynthetic transformations: Gliotoxin (5) is the...
  
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5. Figure 4: Amoebicidal secondary metabolites trypacidin and fumagillin of Aspergillus fumigatus.
  
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6. Figure 5: Intermediates of the DHN-melanin biosynthesis in Aspergillus fumigatus.
  
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7. Figure 6: Intermediates and products of the fumigaclavine C biosynthesis.
  
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8. Figure 7: Bioactive secondary metabolites of Aspergillus fumigatus.
  
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9. Figure 8: Helvolic acid gene cluster of A. fumigatus.
  
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Beilstein J. Org. Chem. 2021, 17, 1814–1827, doi:10.3762/bjoc.17.124

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Development of N-F fluorinating agents and their fluorinations: Historical perspective

Teruo Umemoto,
Yuhao Yang and
Gerald B. Hammond

Review
Published 27 Jul 2021

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1. Graphical Abstract
2. Scheme 1: Fluorination with N-F amine 1-1.
  
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3. Scheme 2: Preparation of N-F amine 1-1.
  
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4. Scheme 3: Reactions of N-F amine 1-1.
  
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5. Scheme 4: Synthesis of N-F perfluoroimides 2-1 and 2-2.
  
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6. Scheme 5: Synthesis of 1-fluoro-2-pyridone (3-1).
  
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7. Scheme 6: Fluorination with 1-fluoro-2-pyridone (3-1).
  
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8. Figure 1: Synthesis of N-F sulfonamides 4-1a–g.
  
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9. Scheme 7: Fluorination with N-F reagent 4-1b,c,f.
  
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10. Scheme 8: Fluorination of alkenyllithiums with N-F 4-1h.
  
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11. Scheme 9: Synthesis of N-fluoropyridinium triflate (5-4a).
  
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12. Scheme 10: Synthetic methods for N-F-pyridinium salts.
  
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13. Figure 2: Synthesis of various N-fluoropyridinium salts. Note: ^athis yield was the one by the improved method...
  
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14. Scheme 11: Fluorination power order of N-fluoropyridinium salts.
  
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15. Scheme 12: Fluorinations with N-F salts 5-4.
  
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16. Scheme 13: Fluorination of Corey lactone 5-7 with N-F-bis(methoxymethyl) salt 5-4l.
  
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17. Scheme 14: Fluorination with NFPy.
  
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18. Scheme 15: Synthesis of the N-F reagent, N-fluoroquinuclidinium fluoride (6-1).
  
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19. Scheme 16: Fluorinations achieved with N-F fluoride 6-1.
  
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20. Scheme 17: Synthesis of N-F imides 7-1a–g.
  
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21. Scheme 18: Fluorination with (CF₃SO₂)₂NF, 7-1a.
  
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22. Scheme 19: Fluorination reactions of various substrates with 7-1a.
  
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23. Scheme 20: Synthesis of N-F triflate 8-1.
  
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24. Scheme 21: Synthesis of chiral N-fluoro sultams 9-1 and 9-2.
  
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25. Scheme 22: Fluorination with chiral N-fluoro sultams 9-1 and 9-2.
  
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26. Scheme 23: Synthesis of saccharin-derived N-fluorosultam 10-2.
  
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27. Scheme 24: Fluorination with N-fluorosultam 10-2.
  
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28. Scheme 25: Synthesis of N-F reagent 11-2.
  
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29. Scheme 26: Fluorination with N-F reagent 11-2.
  
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30. Scheme 27: Synthesis and reaction of N-fluorolactams 12-1.
  
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31. Scheme 28: Synthesis of NFOBS 13-2.
  
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32. Scheme 29: Fluorination with NFOBS 13-2.
  
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33. Scheme 30: Synthesis of NFSI (14-2).
  
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34. Scheme 31: Fluorination with NFSI 14-2.
  
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35. Scheme 32: Synthesis of N-fluorosaccharin (15-1) and N-fluorophthalimide (15-2).
  
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36. Scheme 33: Synthesis of N-F salts 16-3.
  
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37. Scheme 34: Fluorination with N-F salts 16-3.
  
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38. Figure 3: Monofluorination with Selectfluor (16-3a).
  
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39. Figure 4: Difluorination with Selectfluor (16-3a).
  
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40. Scheme 35: Transfer fluorination of Selectfluor (16-3a).
  
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41. Scheme 36: Fluorination of substrates with Selectfluor (16-3a).
  
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42. Scheme 37: Synthesis of chiral N-fluoro-sultam 17-2.
  
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43. Scheme 38: Asymmetric fluorination with chiral 17-2.
  
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44. Figure 5: Synthesis of Zwitterionic N-fluoropyridinium salts 18-2a–h.
  
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45. Scheme 39: Fluorinating power order of zwitterionic N-fluoropyridinium salts.
  
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46. Scheme 40: Fluorination with zwitterionic 18-2.
  
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47. Scheme 41: Activation of salt 18-2h with TfOH.
  
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48. Scheme 42: Synthesis of NFTh, 19-2.
  
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49. Scheme 43: Fluorination with NFTh, 19-2.
  
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50. Scheme 44: Synthesis of 3-fluorobenzo-1,2,3-oxathiazin-4-one 2,2-dioxide (20-2).
  
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51. Scheme 45: Fluorination with 20-2.
  
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52. Scheme 46: Synthesis of N-F amide 21-3.
  
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53. Scheme 47: Fluorination with N-F amide 21-2.
  
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54. Scheme 48: Synthesis of N,N’-difluorodiazoniabicyclo[2.2.2]octane salts 22-1.
  
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55. Scheme 49: One-pot synthesis of N,N’-difluoro-1,4-diazoniabicyclo[2.2.2]octane bistetrafluoroborate salt (22-1d...
  
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56. Figure 6: Fluorination of anisole with 22-1a, d, e.
  
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57. Scheme 50: Fluorination with N,N’-diF bisBF₄ 22-1d.
  
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58. Scheme 51: Synthesis of bis-N-F reagents 23-1–5.
  
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59. Scheme 52: Fluorination with 23-2, 4, 5.
  
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60. Figure 7: Synthesis of N,N’-difluorobipyridinium salts 24-2.
  
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61. Figure 8: Controlled fluorination of N,N’-diF 24-2.
  
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62. Scheme 53: Fluorinating power of N,N’-diF salts 24-2 and N-F salt 5-4a.
  
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63. Scheme 54: Fluorination reactions with Synfluor^TM (24-2b).
  
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64. Scheme 55: Additional fluorination reactions with Synfluor^TM (24-2b).
  
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65. Scheme 56: Synthesis of N-F 25-1.
  
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66. Scheme 57: Fluorination of polycyclic aromatics with 25-1.
  
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67. Scheme 58: Synthesis of 26-1 and dimethyl analog 26-2.
  
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68. Scheme 59: Fluorination with reagents 26-1, 26-2, 1-1, and 26-3.
  
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69. Scheme 60: Synthesis of N-F reagent 27-2.
  
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70. Scheme 61: Synthesis of chiral N-F reagents 27-6.
  
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71. Scheme 62: Synthesis of chiral N-F 27-7–9.
  
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72. Scheme 63: Asymmetric fluorination with 27-6.
  
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73. Scheme 64: Synthesis of chiral N-F reagents 28-3.
  
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74. Scheme 65: Asymmetric fluorination with 28-3.
  
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75. Scheme 66: Synthesis of chiral N-F reagents 28-7.
  
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76. Figure 9: Asymmetric fluorination with 28-7.
  
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77. Scheme 67: In situ formation of N-fluorinated cinchona alkaloids with Selectfluor^TM.
  
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78. Scheme 68: Asymmetric fluorination with N-F alkaloids formed in situ.
  
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79. Scheme 69: Synthesis of N-fluorocinchona alkaloids with Selectfluor.
  
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80. Scheme 70: Asymmetric fluorination with 30-1–4.
  
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81. Scheme 71: Transfer fluorination from various N-F reagents.
  
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82. Figure 10: Asymmetric fluorination of silyl enol ethers.
  
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83. Scheme 72: Synthesis of N-fluoro salt 32-2.
  
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84. Scheme 73: Reactivity of N-fluorotriazinium salt 32-2.
  
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85. Scheme 74: Synthesis of bulky N-fluorobenzenesulfonimide NFBSI 33-3.
  
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86. Scheme 75: Comparison of NFSI and NFBSI.
  
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87. Scheme 76: Synthesis of p-substituted N-fluorobenzenesulfonimides 34-3.
  
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88. Figure 11: Asymmetric fluorination with 34-3 and a chiral catalyst 34-4.
  
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89. Scheme 77: 1,4-Fluoroamination with Selecfluor and a chiral catalyst.
  
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90. Figure 12: Asymmetric fluoroamination with 35-5a, b.
  
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91. Scheme 78: Synthesis of Selectfluor analogs 35-5a, b.
  
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92. Scheme 79: Synthesis of chiral dicationic DABCO-based N-F reagents 36-5.
  
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93. Scheme 80: Asymmetric fluorocyclization with chiral 36-5b.
  
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94. Scheme 81: Synthesis of chiral 37-2a,b.
  
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95. Scheme 82: Asymmetric fluorination with chiral 37-2a,b.
  
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96. Scheme 83: Asymmetric fluorination with chiral 37-2b.
  
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97. Scheme 84: Reaction of indene with chiral 37-2a,b.
  
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98. Scheme 85: Synthesis of Me-NFSI, 38-2.
  
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99. Scheme 86: Fluorination of active methine compounds with Me-NFSI.
  
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100. Scheme 87: Fluorination of malonates with Me-NFSI.
  
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101. Scheme 88: Fluorination of keto esters with Me-NFSI.
  
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102. Scheme 89: Synthesis of N-F 39-3 derived from the ethylene-bridged Tröger’s base.
  
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103. Scheme 90: Fluorine transfer from N-F 39-3.
  
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104. Scheme 91: Fluorination with N-F 39-3.
  
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105. Scheme 92: Synthesis of Selectfluor^CN.
  
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106. Scheme 93: Bistrifluoromethoxylation of alkenes using Selectfluor^CN.
  
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107. Figure 13: Synthesis of NFAS 41-2.
  
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108. Scheme 94: Radical fluorination with different N-F reagents.
  
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109. Scheme 95: Radical fluorination of alkenes with NFAS 41-2.
  
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110. Scheme 96: Radical fluorination of alkenes with NFAS 41-2f.
  
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111. Scheme 97: Decarboxylative fluorination with NFAS 41-2a,f.
  
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112. Scheme 98: Fluorine plus detachment (FPD).
  
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113. Figure 14: FPD values of representative N-F reagents in CH₂Cl₂ and CH₃CN (in parentheses). Adapted with permis...
  
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114. Scheme 99: N-F homolytic bond dissociation energy (BDE).
  
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115. Figure 15: BDE values of representative N-F reagents in CH₃CN. Adapted with permission from ref. [127]. Copyright 2...
  
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116. Figure 16: Quantitative reactivity scale for popular N-F reagents. Adapted with permission from ref. [138], publish...
  
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117. Scheme 100: SET and S_N2 mechanisms.
  
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118. Scheme 101: Radical clock reactions.
  
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119. Scheme 102: Reaction of potassium enolate of citronellic ester with N-F reagents, 10-1, NFSI, and 8-1.
  
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120. Scheme 103: Reaction of compound IV with Selectfluor (OTf) and NFSI.
  
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121. Scheme 104: Reaction of TEMPO with Selecfluor.
  
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Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

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Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

Jongwoo Son

Review
Published 26 Jul 2021

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1. Graphical Abstract
2. Scheme 1: Mn-catalyzed late-stage fluorination of sclareolide (1) and complex steroid 3.
  
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3. Figure 1: Proposed reaction mechanism of C–H fluorination by a manganese porphyrin catalyst.
  
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4. Scheme 2: Late-stage radiofluorination of biologically active complex molecules.
  
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5. Figure 2: Proposed mechanism of C–H radiofluorination.
  
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6. Scheme 3: Late-stage C–H azidation of bioactive molecules. ^a1.5 mol % of Mn(TMP)Cl (5) was used. ^bMethyl acet...
  
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7. Figure 3: Proposed reaction mechanism of manganese-catalyzed C–H azidation.
  
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8. Scheme 4: Mn-catalyzed late-stage C–H azidation of bioactive molecules via electrophotocatalysis. ^a2.5 mol % ...
  
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9. Figure 4: Proposed reaction mechanism of electrophotocatalytic azidation.
  
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10. Scheme 5: Manganaelectro-catalyzed late-stage azidation of bioactive molecules.
  
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11. Figure 5: Proposed reaction pathway of manganaelectro-catalyzed late-stage C–H azidation.
  
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12. Scheme 6: Mn-catalyzed late-stage amination of bioactive molecules. ^a3 Å MS were used. Protonation with HBF₄⋅...
  
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13. Figure 6: Proposed mechanism of manganese-catalyzed C–H amination.
  
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14. Scheme 7: Mn-catalyzed C–H methylation of heterocyclic scaffolds commonly found in small-molecule drugs. ^aDAS...
  
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15. Scheme 8: Examples of late-stage C–H methylation of bioactive molecules. ^aDAST activation. ^bFor insoluble sub...
  
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16. Scheme 9: A) Mn-catalyzed late-stage C–H alkynylation of peptides. B) Intramolecular late-stage alkynylative ...
  
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17. Figure 7: Proposed reaction mechanism of Mn(I)-catalyzed C–H alkynylation.
  
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18. Scheme 10: Late-stage Mn-catalyzed C–H allylation of peptides and bioactive motifs.
  
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19. Scheme 11: Intramolecular C–H allylative cyclic peptide formation.
  
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20. Scheme 12: Late-stage C–H glycosylation of tryptophan analogues.
  
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21. Scheme 13: Late-stage C–H glycosylation of tryptophan-containing peptides.
  
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22. Scheme 14: Late-stage C–H alkenylation of tryptophan-containing peptides.
  
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23. Scheme 15: A) Late-stage C–H macrocyclization of tryptophan-containing peptides and B) traceless removal of py...
  
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Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

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Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

Girish Suresh Yedase,
Sumit Kumar,
Jessica Stahl,
Burkhard König and
Veera Reddy Yatham

Letter
Published 23 Jul 2021

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1. Graphical Abstract
2. Scheme 1: Photocatalyzed aerobic oxidation of aromatic alcohols.
  
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3. Scheme 2: Substrate scope. Reaction conditions as given in Table 1 (entry 1). Yields are isolated yields, average of...
  
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4. Scheme 3: Selective oxidation of 3-bromobenzyl alcohol in the presence of 3-phenylpropanol. Compound 1af was ...
  
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5. Figure 1: Mechanistic studies. (A): UV–vis spectra of the Ce^IV(OBn)Cl_n complex in CH₃CN under blue light irra...
  
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Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

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Correction: Amine–borane complex-initiated SF₅Cl radical addition on alkenes and alkynes

Audrey Gilbert,
Pauline Langowski,
Marine Delgado,
Laurent Chabaud,
Mathieu Pucheault and
Jean-François Paquin

Correction
Published 23 Jul 2021

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1. Graphical Abstract
2. Scheme 1: Corrected Scheme 4 of the original article. Scope of the Et₃B and the DICAB-initiated SF₅Cl additio...
  
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3. Scheme 2: Corrected graphical abstract of the original publication.
  
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Article

Beilstein J. Org. Chem. 2021, 17, 1725–1726, doi:10.3762/bjoc.17.120

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A systems-based framework to computationally describe putative transcription factors and signaling pathways regulating glycan biosynthesis

Theodore Groth,
Rudiyanto Gunawan and
Sriram Neelamegham

Full Research Paper
Published 22 Jul 2021

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1. Graphical Abstract
2. Figure 1: A systems glycobiology framework to link multi-OMICs data. a) Cell signaling proceeds to trigger TF...
  
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3. Figure 2: Analysis workflow: ChiP-Seq provides evidence of TF binding to promoter regions with 0 ≤ RP ≤ 1, qu...
  
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4. Figure 3: Summary of TFs enriched to glycosylation pathways for luminal and basal breast cancer: The TFs foun...
  
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5. Figure 4: Luminal breast cancer signaling pathway enrichment and glycogene connections. a) TF-to-glycogene co...
  
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6. Figure 5: Basal breast cancer signaling pathway enrichments and glycogene connections. a) TF-to-glycogene com...
  
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7. Figure 6: Summary of TF–glycopathway enrichments across all cancer types: TF enrichments to glycopathways acr...
  
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Beilstein J. Org. Chem. 2021, 17, 1712–1724, doi:10.3762/bjoc.17.119

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Volatile emission and biosynthesis in endophytic fungi colonizing black poplar leaves

Christin Walther,
Pamela Baumann,
Katrin Luck,
Beate Rothe,
Peter H. W. Biedermann,
Jonathan Gershenzon,
Tobias G. Köllner and
Sybille B. Unsicker

Full Research Paper
Published 22 Jul 2021

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1. Graphical Abstract
2. Figure 1: Chemical structures of sesquiterpenes emitted from endophytic fungi (Table 2) isolated from black poplar l...
  
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3. Figure 2: Terpene synthase activity of CxTPS1 and CxTPS2. A) Genes were heterologously expressed in Escherich...
  
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4. Figure 3: Dendrogram analysis (rooted tree) of CxTPS1 and CxTPS2 (bold) from Cladosporium sp. and characteriz...
  
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Beilstein J. Org. Chem. 2021, 17, 1698–1711, doi:10.3762/bjoc.17.118

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Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

Susanne M. Fischer,
Simon Renner,
A. Daniel Boese and
Christian Slugovc

Full Research Paper
Published 21 Jul 2021

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1. Graphical Abstract
2. Scheme 1: Mechanism for the phosphine-initiated oxa-Michael addition.
  
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3. Figure 1: Above: Michael acceptors, Michael donors and catalysts used in this study; pK_a (respectively pK_a of...
  
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4. Figure 2: Left: double-bond conversion of the polymerization of 4 initiated by 5 mol % TPP, MMTPP or TMTPP af...
  
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5. Figure 3: Left: Oxidation stability of the phosphines. Phosphine oxide content in % as determined by ³¹P NMR ...
  
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Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

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Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

Nikita Brodyagin,
Martins Katkevics,
Venubabu Kotikam,
Christopher A. Ryan and
Eriks Rozners

Review
Published 19 Jul 2021

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1. Graphical Abstract
2. Figure 1: Structure of DNA and PNA.
  
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3. Figure 2: PNA binding modes: (A) PNA–dsDNA 1:1 triplex; (B) PNA–DNA–PNA strand-invasion triplex; (C) the Hoog...
  
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4. Figure 3: Structure of P-form PNA–DNA–PNA triplex from reference [41]. (A) view in the major groove and (B) view ...
  
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5. Figure 4: Structures of backbone-modified PNA.
  
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6. Figure 5: Structures of PNA having α- and γ-substituted backbones.
  
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7. Figure 6: Structures of modified nucleobases in PNA to improve Hoogsteen hydrogen bonding to guanine and aden...
  
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8. Figure 7: Proposed hydrogen bonding schemes for modified PNA nucleobases designed to recognize pyrimidines or...
  
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9. Figure 8: Modified nucleobases to modulate Watson–Crick base pairing and chemically reactive crosslinking PNA...
  
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10. Figure 9: Examples of triplets formed by Janus-wedge PNA nucleobases (blue). R¹ denotes DNA, RNA, or PNA back...
  
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11. Figure 10: Examples of fluorescent PNA nucleobases. R¹ denotes DNA, RNA, or PNA backbones.
  
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12. Figure 11: Endosomal entrapment and escape pathways of PNA and PNA conjugates.
  
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13. Figure 12: (A) representative cell-penetrating peptides (CPPs), (B) conjugation designs and linker chemistries....
  
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14. Figure 13: Proposed delivery mode by pHLIP-PNA conjugates (A) the transmembrane section of pHLIP interacting w...
  
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15. Figure 14: Structures of modified penetratin CPP conjugates with PNA linked through either disulfide (for stud...
  
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16. Figure 15: Chemical structure of C₉–PNA, a stable amphipathic (cyclic-peptide)–PNA conjugate.
  
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17. Figure 16: Structures of PNA conjugates with a lipophilic triphenylphosphonium cation (TPP–PNA) through (A) th...
  
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18. Figure 17: Structures of (A) chloesteryl–PNA, (B) cholate–PNA and (C) cholate–PNA(cholate)₃.
  
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19. Figure 18: Structures of PNA–GalNAc conjugates (A) (GalNAc)₂K, (B) triantennary (GalNAc)₃, and (C) trivalent (...
  
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20. Figure 19: Vitamin B₁₂–PNA conjugates with different linkages.
  
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21. Figure 20: Structures of (A) neomycin B, (B) PNA–neamine conjugate, and (C) PNA–neosamine conjugate.
  
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22. Figure 21: PNA clamp (red) binding to target DNA containing a mixture of sequences (A) PNA binds with higher a...
  
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23. Figure 22: Rolling circle amplification using PNA openers (red) to invade a dsDNA target forming a P-loop. A p...
  
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24. Figure 23: Molecular beacons containing generic fluorophores (Fl) and quenchers (Q) recognizing a complementar...
  
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25. Figure 24: (A) Light-up fluorophores such as thiazole orange display fluorescence enhancement upon binding to ...
  
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26. Figure 25: Templated fluorogenic detection of oligonucleotides using two PNAs. (A) Templated FRET depends on h...
  
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27. Figure 26: Lateral flow devices use a streptavidin labeled strip on nitrocellulose paper to anchor a capture P...
  
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Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

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2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

Najeh Tka,
Mohamed Adnene Hadj Ayed,
Mourad Ben Braiek,
Mahjoub Jabli,
Noureddine Chaaben,
Kamel Alimi,
Stefan Jopp and
Peter Langer

Full Research Paper
Published 16 Jul 2021

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1. Graphical Abstract
2. Figure 1: Applications of acridines.
  
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3. Scheme 1: Synthesis of 2,4-dibromo-9-chloro-5,6,7,8-tetrahydroacridine (2).
  
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4. Scheme 2: Synthesis of 2,4-bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines 4a–g.
  
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5. Figure 2: UV–vis absorption spectra of 4a,b and 4e–g in diluted dichloromethane solutions at room temperature...
  
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6. Figure 3: Emission spectra of 4a,b and 4e–g in diluted dichloromethane solutions at room temperature (c = 1 ×...
  
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Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

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