Base-catalyzed reactions. XXXVII. Relative rates of side-chain alkenylation of 4-substituted pyridines with isoprene. Effects of the side-chain double bond on reaction rates

1970 ◽  
Vol 35 (2) ◽  
pp. 422-426 ◽  
Author(s):  
Wayne M. Stalick ◽  
Herman. Pines
Keyword(s):  
Double Bond ◽  
Reaction Rates ◽  
Side Chain ◽  
Substituted Pyridines ◽  
Catalyzed Reactions

A Novel Scheme for the Synthesis of 21-Acetoxypregna-1,4,9(11)-triene- 17α,21-diol-3,20-dione from 9α-Hydroxyandrostenedione

2020 ◽  
Vol 16 (5) ◽  
pp. 606-610
Author(s):  
Nguyen T. Diep ◽  
Luu D. Huy
Keyword(s):  
Double Bond ◽  
Chemical Synthesis ◽  
Economic Efficiency ◽  
Final Stage ◽  
Side Chain ◽  
Entire Process ◽  
Drug Synthesis ◽  
First Time

Background: Vietnam currently imports up to 90% of the pharmaceuticals it consumes and 100% of the steroid-based pharmaceuticals. The ability for efficient chemical synthesis of the steroids could create commercial opportunities to address this issue. Synthesis of 21-acetoxypregna-1,4,9(11)- triene-17α,21-diol-3,20-dione is considered a key intermediate in the scheme of steroidal drug synthesis. Previous synthesis attempts of such steroids (corticoids) introduce a double bond at C-1(2) in the final stage of synthesis, which delivers a poor yield and reduces the economic efficiency of the process. Objective: To study and develop a novel and effective method for the synthesis of 21-acetoxypregna- 1,4,9(11)-triene-17α,21-diol-3,20-dione. Methods: Using 9α-hydroxyandrostenedione as a substrate chemical synthesis was performed as follows: pregnane side chain construction at C-17 (acetylene method), introduction of C-1(2) double bond (using SeO2), epimerization of C-17 (via 17-ONO2 ester) and Stork’s iodination. Results: 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione was prepared from 9α- hydroxyandrostenedione with an improved yield compared to previous attempts. Conclusion: Here, 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione has been synthesized from 9α-hydroxyandrostenedione based on a novel, effective and commercially feasible scheme. The introduction of the C-1(2) double bond at an earlier stage of the synthesis has increased the economic efficiency of the entire process. For the first time, the indirect epimerization mechanism has been clarified along with the configuration of the C-17 stereo-center which has been confirmed using NOESY data.

Critical Review of Biotransformational Studies on Steroids by Using Culture of Cunninghamella blakesleeana

2021 ◽  
Vol 18 ◽  
Author(s):  
Azizuddin ◽  
Muhammad Iqbal ◽  
Syed Ghulam Musharraf
Keyword(s):  
Double Bond ◽  
Critical Review ◽  
Structural Modification ◽  
Bond Formation ◽  
Environmentally Friendly ◽  
Side Chain ◽  
Synthetic Compounds ◽  
Efficient Approach ◽  
Cunninghamella Blakesleeana ◽  
Different Strains

: For several decades, biotransformational studies on steroidal compounds have gained a lot of attention because it is an efficient approach for the structural modification of complicated natural or synthetic compounds with high regio-, chemo- and stereoselectivity at environmentally friendly conditions. This review summarizes the use of different strains of Cunninghamella blakesleeana for the biotransformation of sixteen steroids 1-16 into a variety of transformed products. The transformed products may be important as a drug or precursor for the production of important pharmaceuticals. The types of reactions performed by C. blakesleeana include hydroxylation, epoxidation, reduction, demethylation, oxidation, glycosidation, double bond formation, side-chain degradation, isomerisation and opening of an isoxazol ring, which would be difficult to produce by traditional synthesis.

Migration of the Double Bond in the Side Chain of Sterols with Iodine.

1970 ◽  
Vol 35 (12) ◽  
pp. 4145-4148 ◽  
Author(s):  
Nobuo Ikekawa ◽  
Yasushi Honma ◽  
Naoko Morisaki ◽  
Kiyoshi Sakai
Keyword(s):  
Double Bond ◽  
Side Chain

Reactions of N-tricyanovinylamines with thiols in aqueous solutions

1990 ◽  
Vol 55 (6) ◽  
pp. 1630-1634 ◽  
Author(s):  
Dušan Podhradský ◽  
Helena Paulíková ◽  
Ján Imrich
Keyword(s):  
Double Bond ◽  
Aqueous Solutions ◽  
Reaction Rates ◽  
Imino Group ◽  
Group A ◽  
Kinetics Of

Kinetics of reactions between N-substituted tricyanovinylamines and thiols, where primarily reduction of the C=C double bond takes place, was investigated under conditions adequate to physiological ones. The reaction rates did not depend either on the type of the reacting thiol, or on the pH of the medium, but they decreased with the increasing pKa value of the imino group. A quantitative conversion of the thiol peptide glutathione to its oxidized form was evidenced.

Temperature, Dynamics, and Enzyme-Catalyzed Reaction Rates

2020 ◽  
Vol 49 (1) ◽  
pp. 163-180 ◽  
Author(s):  
Vickery L. Arcus ◽  
Adrian J. Mulholland
Keyword(s):  
Molecular Mechanisms ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Rate Theory ◽  
Different Temperatures ◽  
State Ensemble ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Transition State Ensemble ◽  
Rate Limiting

We review the adaptations of enzyme activity to different temperatures. Psychrophilic (cold-adapted) enzymes show significantly different activation parameters (lower activation enthalpies and entropies) from their mesophilic counterparts. Furthermore, there is increasing evidence that the temperature dependence of many enzyme-catalyzed reactions is more complex than is widely believed. Many enzymes show curvature in plots of activity versus temperature that is not accounted for by denaturation or unfolding. This is explained by macromolecular rate theory: A negative activation heat capacity for the rate-limiting chemical step leads directly to predictions of temperature optima; both entropy and enthalpy are temperature dependent. Fluctuations in the transition state ensemble are reduced compared to the ground state. We show how investigations combining experiment with molecular simulation are revealing fundamental details of enzyme thermoadaptation that are relevant for understanding aspects of enzyme evolution. Simulations can calculate relevant thermodynamic properties (such as activation enthalpies, entropies, and heat capacities) and reveal the molecular mechanisms underlying experimentally observed behavior.

Enaminones as Building Blocks In Heterocyclic Synthesis: A New One Pot Synthesis of Polyfunctional Substituted Pyridines

2001 ◽  
Vol 56 (10) ◽  
pp. 1074-1078 ◽  
Author(s):  
Samia Michel Agamy ◽  
Mervat Mohammed Abdel-Khalik ◽  
Mona Hassan Mohamed ◽  
Mohammed Hilmy Elnagdi
Keyword(s):  
Acetic Acid ◽  
Double Bond ◽  
Aromatic Aldehyde ◽  
Michael Addition ◽  
Ammonium Acetate ◽  
Building Blocks ◽  
Heterocyclic Synthesis ◽  
One Pot ◽  
Active Methyl ◽  
Substituted Pyridines

Enaminones react with a variety of active methyl and methylene reagents in presence of ammonium acetate to yield functionally substituted pyridines in good yields. The reaction proceeded via initial Michael addition across the double bond followed by cyclization. The reaction of enaminone with aromatic aldehyde in acetic acid/ammonium acetate afforded the dihydropyridine that was oxidized to the corresponding pyridine.

Extractives of Australian timbers. X. Autoxidation and other reactions of the conjugated side-chain of eberlin lactone. Isolation of a new isomer of ebelin lactone

1970 ◽  
Vol 23 (10) ◽  
pp. 2085 ◽  
Author(s):  
RA Eade ◽  
J Ellis ◽  
JS Shannon ◽  
HV Simes ◽  
JJH Simes
Keyword(s):  
Double Bond ◽  
Solid State ◽  
Osmium Tetroxide ◽  
Side Chain ◽  
Methyl Groups ◽  
Stepwise Manner ◽  
Terminal Double Bond ◽  
Conjugated Triene

The conjugated triene side-chain of ebelin lactone has been degraded in a stepwise manner using osmium tetroxide. A new isomer of ebelin lactone has been isolated from the sapogenin mixture and has been assigned the structure (9) in which the 25(26) double bond has the cis configuration. Autoxidation of ebelin lactone in the solid state yields a mixture from which three compounds have been isolated and identified; all three arise from oxidation of the side-chain at the terminal double bond and methyl groups.

scholarly journals Triterpene Glycosides from the Sea Cucumber Eupentacta Fraudatrix. Structure and Biological Action of Cucumariosides I1, I3, I4, Three New Minor Disulfated Pentaosides

2013 ◽  
Vol 8 (8) ◽  
pp. 1934578X1300800 ◽  
Author(s):  
Alexandra S. Silchenko ◽  
Anatoly I. Kalinovsky ◽  
Sergey A. Avilov ◽  
Pelageya V. Andryjaschenko ◽  
Pavel S. Dmitrenok ◽  
...  
Keyword(s):  
Double Bond ◽  
Sea Cucumber ◽  
2D Nmr ◽  
Triterpene Glycosides ◽  
Side Chain ◽  
Ehrlich Carcinoma ◽  
Cytotoxic Activities ◽  
Moderate Activity ◽  
2D Nmr Spectroscopy ◽  
Eupentacta Fraudatrix

Three new minor triterpene glycosides, cucumariosides I1 (1), I3 (2) and I4 (3) have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. Structures of the glycosides were elucidated by 2D NMR spectroscopy and MS. Glycosides 1–3 belong to the group of cucumariosides I, having branched pentasaccharide carbohydrate moieties with two sulfate groups and possessing 3- O-methyl-D-xylose as a terminal monosaccharide unit that is a characteristic feature of all the glycosides isolated from E. fraudatrix. Glycosides 1 and 2 differ from each other by the side chain structures in the holostane aglycone moieties, while cucumarioside I4 (3) has a 23,24,25,26,27-pentanorlanostane aglycone with an 18(16)-lactone. Cytotoxic activities of glycosides 1–3 against mouse spleen lymphocytes and ascite form of mouse Ehrlich carcinoma cells, along with hemolytic activity against mouse erythrocytes and antifungal activity were studied. Glycoside 1, having an aglycone side chain with a 24(25)-double bond, possesses moderate activity in all the tests, while glycoside 2, having 23(24)-double bond and 25-hydroxy group in the side chain, and glycoside 3 with an aglycone with an 18(16)-lactone and shortened side chain have either low activity or are non-active.

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