Oxidation of emodin anthrone and stereochemistry of emodin bianthrone

1976 ◽  
Vol 29 (7) ◽  
pp. 1535 ◽  
Author(s):  
DW Cameron ◽  
JS Edmonds ◽  
WD Raverty
Keyword(s):  
Oxidative Coupling ◽  
Shift Reagent ◽  
Major Product ◽  
Dimethyl Sulphoxide ◽  
Controlled Synthesis ◽  
Mild Oxidation ◽  
Emodin Anthrone

Synthetic emodin bianthrone is separated into meso- and (�)-diastereomers which are identified by means of an asymmetric p.m.r. shift reagent. They behave differently on mild oxidation. Both give protohypericin accompanied by an anthraquinone fraction but, whereas the major anthraquinone from the meso is emodin, the (k) gives chiefly the bianthraquinonyl, skyrin. This difference is accounted for in terms of the geometry of oxidative coupling. Oxidation of emodin anthrone in alkaline dimethyl sulphoxide gives a l,4-anthraquinone as major product. The scope of this novel oxidation has been extended to other anthrones and it has been utilized in the controlled synthesis of purpurin derivatives. It may involve anthrslnol tautomers as intermediates.

Diels–Alder Cycloaddition: Fawcettimine (Zhai), Sculponeatin N (Zhai), Elansolid B1 (Kirschning), Frondosin A (Wright), Kingianin H (Parker), Rufescenolide (Snyder)

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Microwave Irradiation ◽  
Radical Cation ◽  
Oxidative Coupling ◽  
Major Product ◽  
Diels Alder ◽  
Intramolecular Cycloaddition ◽  
Ru Complex ◽  
Cyclic Enones ◽  
The University ◽  
University Of Connecticut

En route to fawcettimine 4, Hongbin Zhai of Lanzhou University found (Org. Lett. 2014, 16, 196) that microwave irradiation improved the efficiency of the cyclo­addition of the enone 1 with butadiene 2 to give 3. Takuya Kurahashi and Seijiro Matsubara of Kyoto University developed (Org. Lett. 2014, 16, 2594) a Ru complex that promoted the cycloaddition of butadiene with cyclic enones. In the course of a synthesis of sculponeatin N 7, Professor Zhai employed (Org. Lett. 2014, 16, 216) the silyl diene 5. After intramolecular cycloaddition, protonation of the resulting allyl silane with concomitant alkene migration led to the adduct 6. On the way to elansolid B1 10, Andreas Kirschning of Leibnitz Universität Hannover oxidized (Org. Lett. 2014, 16, 568) the alcohol 8 to the enone, that cyclized to 9. Under the influence of MgBr2, the cyclization proceeded with remarkable diastereocontrol. Dennis L. Wright of the University of Connecticut began (J. Am. Chem. Soc. 2014, 136, 4309) the synthesis of frondosin A 13 by preparing the secondary ether 11 in high ee. Diels–Alder cycloaddition of tetrabromocyclopropene gave, after exposure of the initial adduct to water, the dibromoenone 12. Kathlyn A. Parker of Stony Brook University explored (J. Org. Chem. 2014, 79, 919) the amine radical cation-promoted intermolecular Diels–Alder cycloaddition of the bicyclooctadiene 14. Three readily-separated diastereomeric dimers were observed. The diol 15, the precursor to kingianin H 16, was the major product. Scott A. Synder of Scripps/Florida described (J. Org. Chem. 2014, 79, 88) the interesting oxidative coupling of 17 with 18. The product 19 was readily carried on to rufescenolide 20.

METABOLISM OF 17α-HYDROXYPROGESTERONE-4-14C-17α-CAPROATE BY HOMOGENATES OF RAT LIVER AND HUMAN PLACENTA

1961 ◽  
Vol 36 (4) ◽  
pp. 511-519 ◽  
Author(s):  
Margaret Wiener ◽  
Charles I. Lupa ◽  
E. Jürgen Plotz
Keyword(s):  
Rat Liver ◽  
Human Placenta ◽  
Steric Hindrance ◽  
Placental Tissue ◽  
Caproic Acid ◽  
Major Product ◽  
Side Chain ◽  
Anaerobic Conditions ◽  
Prolonged Action ◽  
Long Acting

ABSTRACT 17α-hydroxyprogesterone-4-14C-17α-caproate (HPC), a long-acting progestational agent, was incubated with homogenates of rat liver and human placenta. The rat liver was found to reduce Ring A of HPC under anaerobic conditions to form allopregnane-3β,17α-diol-20-one-17α-caproate and pregnane-3β,17α-diol-20-one-17α-caproate, the allopregnane isomer being the major product. The caproic acid ester was neither removed nor altered during the incubation. Placental tissue did not attack HPC under conditions where the 20-ketone of progesterone was reduced. It is postulated that this absence of attack on the side chain is due to steric hindrance from the caproate ester, and that this may account for the prolonged action of HPC.

Seeded Growth of Single-Crystal Two-Dimensional Covalent Organic Frameworks

2017 ◽  
Author(s):  
Austin M. Evans ◽  
Lucas R. Parent ◽  
Nathan C. Flanders ◽  
Ryan P. Bisbey ◽  
Edon Vitaku ◽  
...  
Keyword(s):  
Molecular Transport ◽  
Controlled Synthesis ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Seeded Growth ◽  
Covalent Bonds ◽  
Crystalline Materials ◽  
Step Procedure ◽  
Structures And Properties ◽  
2D Polymer

<div> <div> <div> <p>Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, atomically thin macromolecular sheets linked by robust, covalent bonds. These materials exhibit desirable mechanical, optoelectrotronic, and molecular transport properties derived from their designed structure and permanent porosity. 2D covalent organic frameworks (COFs) offer broad monomer scope, but are generally isolated as polycrystalline, insoluble powders with limited processability. Here we overcome this limitation by controlling 2D COF formation using a two- step procedure. In the first step, 2D COF nanoparticle seeds are prepared with approximate diameters of 30 nm. Next, monomers are slowly added to suppress new nucleation while promoting epitaxial growth on the existing seeds to sizes of several microns. The resulting COF nanoparticles are of exceptional and unprecedented quality, isolated as single crystalline materials with micron-scale domain sizes. These findings advance the controlled synthesis of 2D layered COFs and will enable a broad exploration of synthetic 2D polymer structures and properties. </p> </div> </div> </div>

Seeded Growth of Single-Crystal Two-Dimensional Covalent Organic Frameworks

2017 ◽  
Author(s):  
Austin M. Evans ◽  
Lucas R. Parent ◽  
Nathan C. Flanders ◽  
Ryan P. Bisbey ◽  
Edon Vitaku ◽  
...  
Keyword(s):  
Molecular Transport ◽  
Controlled Synthesis ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Seeded Growth ◽  
Covalent Bonds ◽  
Crystalline Materials ◽  
Step Procedure ◽  
Structures And Properties ◽  
2D Polymer

<div> <div> <div> <p>Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, atomically thin macromolecular sheets linked by robust, covalent bonds. These materials exhibit desirable mechanical, optoelectrotronic, and molecular transport properties derived from their designed structure and permanent porosity. 2D covalent organic frameworks (COFs) offer broad monomer scope, but are generally isolated as polycrystalline, insoluble powders with limited processability. Here we overcome this limitation by controlling 2D COF formation using a two- step procedure. In the first step, 2D COF nanoparticle seeds are prepared with approximate diameters of 30 nm. Next, monomers are slowly added to suppress new nucleation while promoting epitaxial growth on the existing seeds to sizes of several microns. The resulting COF nanoparticles are of exceptional and unprecedented quality, isolated as single crystalline materials with micron-scale domain sizes. These findings advance the controlled synthesis of 2D layered COFs and will enable a broad exploration of synthetic 2D polymer structures and properties. </p> </div> </div> </div>

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