New Heterocyclic Analogues of Anthracycline Antibiotics
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ABSTRACT Synthetic approaches to anthracycline antibiotic analogues in which the nitrogen atom of the carbohydrate portion is incorporated into a 1, 2, 3-triazolyl moiety were investigated. By using methyl 6-azido-2, 6-dideoxy-β-D--arabino-hexopyranoside and methyl 6-azido-2, 3, 6-tricdeoxy--α-L-arabino-hexopyranoside, the corresponding glycosides (16 a, b - 18 a, b) of carminomycinone and daunomycinone were prepared. The desired heterocyclic system was developed directly with the C-3′ and C-6′ azido anthracyclines by means of a cycloaddition process to give 7-0-[6′-(4, 5--dicarboethoxy-l, 2, 3-triazolyl)-2′, 6′-dideoxy-β-D-arabino--hexopyranosyl]-carminomycinone (23) and -daunomycinone (22), and 3′-(4, 5-dicarboethoxy - l, 2, 3-triazolyl)-4′ -epi-daunomycin (24).Keywords:
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This chapter contains sections titled: 2 + 2-Cycloaddition 2 + 3-Cycloaddition 2 + 4-Cycloaddition Miscellaneous Cycloadditions References
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In the course of the development of new herbicide (MK-616: N-(p-chlorophenyl)-3, 4, 5, 6-tetrahydrophthalimide), the structure-activity relationship of cyclic imide herbicides was investigated. Sixty N-substituted phenyl-3, 4, 5, 6-tetrahydrophthalimides and related compounds were prepared and their herbicidal activity were examined. The results indicate that, for high inhibitory activity, lipophilic tetramethylene moiety, double bond or nitrogen atom (s) in bridgehead position and N-(p-substituted) phenyl moiety are essential in these cyclic imides. New 4-(p-chlorophenyl)-1, 2-tetramethyleneurazole and 3 (p-chlorophenyl)-1, 5-tetramethylenehydantoin were found to be herbicidally active.
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Imide
Nitrogen atom
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This chapter contains sections titled: (2 + 2)-Cycloaddition (2 + 3)-Cycloaddition (2 + 4)-Cycloaddition Miscellaneous References The recent developments of the enantioselective gold(I)-catalysed cycloaddition reactions (2+2, 3+3, 4+2, and 4+3) have been extensively reviewed. The mechanisms of transition-metal-catalysed (2+2)–cycloaddition reactions between bicyclic alkenes and alkynes have been thoroughly reviewed. The rutheniumcatalysed asymmetric (2+2)–cycloaddition reactions of chiral acyl camphorsultamsubstituted alkynes with bicyclic alkenes formed bicyclic cyclobutenes with good yields and enantioselectivity. The formal (2+2)– cycloaddition is thought to involve an initial (3+2)–cycloaddition. Chiral air-stable ferrocenylphosphines promote the asymmetric (3+2)–cycloaddition of Morita-Baylis-Hillman carbonates with maleimides to form multifunctional cyclopentenes in reasonable yield and enantioselectivity. A review of the use of organocatalysts in the (3+2)–cycloaddition reactions of azomethine ylides to produce pyrrolidine derivatives has been published. The Diels-Alder cycloaddition of allylidenecyclopropane with a variety of cyclic and acyclic dienophiles provides a pathway to the tricyclic ring system of the Illudin group of natural products.
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The reaction mechanism and regioselectivity of cycloaddition reactions of benzyne to armchair single-walled carbon nanotubes were investigated with quantum chemical methods. The [2 + 2] cycloaddition reaction follows the diradical mechanism, whereas the [4 + 2] cycloaddition reaction adopts the concerted mechanism. More importantly, the [2 + 2] product is always more stable thermodynamically than the [4 + 2] ones, regardless of the diameter, while the [4 + 2] cycloaddition becomes kinetically more favored as the diameter goes up.
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The enantioselective N-heterocyclic carbene-catalysed formal 2+2- and 2+2+2- cycloadditions of ketenes with isothiocyanates can be investigated. At room temperature, the reaction of N-arylthiocyanates favours the 2+2-cycloaddition. However, at −40°C, N-benzoylisothiocyanates undergo the 2+2+2-cycloaddition. This chapter discusses cycloaddition-type addition reactions. Specifically, it covers three types of cycloadditions: 2+2-cycloaddition, 2+3-cycloaddition and 2+4-cycloaddition. Miscellaneous cycloaddition reactions are separately described at the end of the chapter.
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We synthesized [2]rotaxanes with a pyrrole moiety from a [2]rotaxane with a 1,3-diynyl moiety. The conversion of the 1,3-diynyl moiety of the axle component to the pyrrole moiety was accomplished by a Cu-mediated cycloaddition of anilines. The cycloaddition reaction was accelerated when the [2]rotaxane was used as the substrate. The effect of the structure of the pyrrole moiety on the rate of the shuttling was studied.
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Rotaxane
Pyrrole
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Abstract Metal-catalyzed [2+2+2] cycloaddition is a powerful tool that allows rapid construction of functionalized 6-membered carbo- and heterocycles in a single step through an atom-economical process with high functional group tolerance. The reaction is usually regio- and chemoselective although selectivity issues can still be challenging for intermolecular reactions involving the cross-[2+2+2] cycloaddition of two or three different alkynes and various strategies have been developed to attain high selectivities. Furthermore, enantioselective [2+2+2] cycloaddition is an efficient means to create central, axial, and planar chirality and a variety of chiral organometallic complexes can be used for asymmetric transition-metal-catalyzed inter- and intramolecular reactions. This review summarizes the recent advances in the field of [2+2+2] cycloaddition. 1 Introduction 2 Formation of Carbocycles 2.1 Intermolecular Reactions 2.1.1 Cyclotrimerization of Alkynes 2.1.2 [2+2+2] Cycloaddition of Two Different Alkynes 2.1.3 [2+2+2] Cycloaddition of Alkynes/Alkenes with Alkenes/Enamides 2.2 Partially Intramolecular [2+2+2] Cycloaddition Reactions 2.2.1 Rhodium-Catalyzed [2+2+2] Cycloaddition 2.2.2 Molybdenum-Catalyzed [2+2+2] Cycloaddition 2.2.3 Cobalt-Catalyzed [2+2+2] Cycloaddition 2.2.4 Ruthenium-Catalyzed [2+2+2] Cycloaddition 2.2.5 Other Metal-Catalyzed [2+2+2] Cycloaddition 2.3 Totally Intramolecular [2+2+2] Cycloaddition Reactions 3 Formation of Heterocycles 3.1 Cycloaddition of Alkynes with Nitriles 3.2 Cycloaddition of 1,6-Diynes with Cyanamides 3.3 Cycloaddition of 1,6-Diynes with Selenocyanates 3.4 Cycloaddition of Imines with Allenes or Alkenes 3.5 Cycloaddition of (Thio)Cyanates and Isocyanates 3.6 Cycloaddition of 1,3,5-Triazines with Allenes 3.7 Cycloaddition of Aldehydes with Enynes or Allenes/Alkenes 3.8 Totally Intramolecular [2+2+2] Cycloaddition Reactions 4 Conclusion
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Abstract Acetylene and ethylene are the smallest molecules that contain an unsaturated carbon–carbon bond and can be efficiently utilized in a large variety of cycloaddition reactions. In this review, we summarize the application of these C2 molecular units in cycloaddition chemistry and highlight their amazing synthetic opportunities. 1 Introduction 2 Fundamental Features and Differences of Cycloaddition Reactions Involving Acetylene and Ethylene 3 (2+1) Cycloaddition 4 [2+2] Cycloaddition 5 (3+2) Cycloaddition 6 [4+2] Cycloaddition 7 (2+2+1) Cycloaddition 8 [2+2+2] Cycloaddition 9 The Use of Acetylene and Ethylene Cycloaddition for Deuterium and 13C Labeling 10 Conclusions
Acetylene
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This Chapter Contains Sections titled: 2 + 2-Cycloaddition 2 + 3-Cycloaddition 2 + 4-Cycloaddition Miscellaneous Cycloadditions References A review of advances in Nickel-catalysed cycloaddition reactions directed towards the synthesis of carbocycles and heterocycles has been presented. The discussion includes the development and mechanistic studies of the Ni/NHC catalysts that couple diynes and nitriles to form pyridines. The use of vinyl cyclopropanes, aldehydes, ketones, tropones, 3-azetidinones, and 3-oxetenones as substrates in new Ni-catalysed cycloaddition reactions is also discussed. A second extensive review concerning Ni-catalysed cycloaddition reactions that have been studied since 2004 has been published. 1,3-Dipolar cycloadditions, Diels-Alder cycloadditions, 2+2+2- cycloadditions, and 3+3-cycloadditions are discussed. NHC-stabilized silylene monohydride reacted with diphenylacetylene to yield a 2,3,4,5-tetraphenyl-1-(tri-t-butylsilyl)-1H-silole via a 2+2+1-cycloaddition. DFT calculations indicate that the reaction mechanism did not include a silirene, the typical 2+1-cycloaddition product. The Rhodium-catalysed enantioselective 2+2+2-cycloaddition of silicon-containing prochiral triynes and internal alkynes yielded silicon-stereogenic dibenzosiloles with high enantoselectivities and high yields.
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Diphenylacetylene
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Objective To develop a new series of hydroxyethylamine (HEA) BACE1 inhibitors with nitrogen heterocyclic moiety at N-terminal and find new N-terminal moiety for enhancing BACE1 inhibition activity. Methods New HEA compounds with nitrogen heterocyclic moiety at N-terminal were synthesized and evaluated as BACE1 inhibitors,with (-)-epigallocatechin-3gallate EGCG as a positive control. Results All new compounds were characterized by 1H NMR and ESI-MS. Evaluation of BACE1 inhibition activity showed that the compound Ⅰ6 with indole moiety at N-terminal had BACE1 inhibition activity. Conclusion The results suggested that the indole moiety at N-terminal interact with S2 pocket of BACE1 and be favorable for enhancing BACE1 inhibition activity, Thus, the indole moiety at N-terminal can be used as lead structure for further finding more effient BACE1 inhibitors.
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