scholarly journals Enantioselective synthesis of Iboga alkaloids and vinblastine via rearrangements of quaternary ammoniums

2016 ◽  
Vol 7 (8) ◽  
pp. 5530-5536 ◽  
Author(s):  
Yun Zhang ◽  
Yibin Xue ◽  
Gang Li ◽  
Haosen Yuan ◽  
Tuoping Luo
Keyword(s):  
Enantioselective Synthesis ◽  
Stevens Rearrangement ◽  
Enantioselective Syntheses ◽  
Catalyzed Oxidation

We present an efficient and unified strategy for the enantioselective syntheses of various iboga alkaloids and vinblastine, involving gold-catalyzed oxidation and Stevens rearrangement. New vinblastine analogs were prepared by our 10-step synthesis.

Enantioselective Syntheses of Flavonoid Diels-Alder Natural Products: A Review

2018 ◽  
Vol 15 (2) ◽  
pp. 221-229 ◽  
Author(s):  
Shah Bakhtiar Nasir ◽  
Noorsaadah Abd Rahman ◽  
Chin Fei Chee
Keyword(s):  
Natural Products ◽  
Organic Synthesis ◽  
Lewis Acid ◽  
Alder Reaction ◽  
Diels Alder ◽  
Enantioselective Synthesis ◽  
Chiral Ligand ◽  
Asymmetric Syntheses ◽  
Diels Alder Reaction ◽  
Enantioselective Syntheses

Background: The Diels-Alder reaction has been widely utilised in the syntheses of biologically important natural products over the years and continues to greatly impact modern synthetic methodology. Recent discovery of chiral organocatalysts, auxiliaries and ligands in organic synthesis has paved the way for their application in Diels-Alder chemistry with the goal to improve efficiency as well as stereochemistry. Objective: The review focuses on asymmetric syntheses of flavonoid Diels-Alder natural products that utilize chiral ligand-Lewis acid complexes through various illustrative examples. Conclusion: It is clear from the review that a significant amount of research has been done investigating various types of catalysts and chiral ligand-Lewis acid complexes for the enantioselective synthesis of flavonoid Diels-Alder natural products. The results have demonstrated improved yield and enantioselectivity. Much emphasis has been placed on the synthesis but important mechanistic work aimed at understanding the enantioselectivity has also been discussed.

scholarly journals Chemoenzymatic enantioselective synthesis of baclofen

1994 ◽  
Vol 72 (11) ◽  
pp. 2312-2317 ◽  
Author(s):  
Robert Chênevert ◽  
Michel Desjardins
Keyword(s):  
Enzymatic Hydrolysis ◽  
Acetic Anhydride ◽  
Aqueous Medium ◽  
Organic Medium ◽  
Enantioselective Synthesis ◽  
Enantioselective Syntheses ◽  
Hydrolysis Of

We report two different chemoenzymatic enantioselective syntheses of baclofen based on the distinction between enantiotopic ester groups in compounds bearing a prochiral centre. In the first approach, the key step is the highly stereoselective enzymatic hydrolysis of dimethyl 3-(4-chlorophenyl)glutarate by chymotrypsin in an aqueous medium. In the second approach, the key step is the enzyme-catalyzed esterification of 2-(4-chloropheny 1)-1,3-propanediol by acetic anhydride in the presence of a lipase in an organic medium.

scholarly journals Enantioselective Synthesis of Natural Trinorsesquiterpene Tetralones by Chemo-enzymatic Approaches

2013 ◽  
Vol 8 (7) ◽  
pp. 1934578X1300800 ◽  
Author(s):  
Stefano Serra
Keyword(s):  
Absolute Configuration ◽  
Building Blocks ◽  
Enantioselective Synthesis ◽  
Ring Closure ◽  
Baker's Yeast ◽  
Key Steps ◽  
First Time ◽  
Enantioselective Syntheses ◽  
Mediated Reduction ◽  
Very High

The enantioselective syntheses of both the enantiomeric forms of the four natural tetralones 1a-d are here described. The aforementioned trinorsesquiterpenes were prepared starting either from substituted ( S)-3-arylbutanols 5a-c or from substituted ( S)-2-arylpropanols 7a-c. The latter chiral building blocks were in turn obtained through two different kinds of enzymatic transformations consisting of the baker's yeast mediated reduction of substituted ( E)-3-aryl-but-2-enals 4a-c and the lipase-mediated resolution of racemic 2-arylpropanols 7a-c, respectively. Further key steps of the presented syntheses were C1 and C2 homologation procedures as well as the ring closure of the substituted 4-aryl-pentanoic acids 3a-c. By these means the target compounds were obtained in good yields and with very high stereoisomeric purity. In addition, the trinorsesquiterpene schiffnerone-B was synthesized for the first time and its absolute configuration was unambiguously assigned.

Efficient stereoselective syntheses of piperidine, pyrrolidine, and indolizidine alkaloids

2001 ◽  
Vol 73 (3) ◽  
pp. 573-578 ◽  
Author(s):  
Dieter Enders ◽  
Christoph Thiebes
Keyword(s):  
Double Bond ◽  
Enantioselective Synthesis ◽  
Mexican Bean Beetle ◽  
Indolizidine Alkaloids ◽  
Recent Advances ◽  
Bean Beetle ◽  
Pyrrolidine Alkaloids ◽  
Stereoselective Syntheses ◽  
Enantioselective Syntheses

Recent advances in the diastereo- and enantioselective synthesis of piperidine, pyrrolidine, and indolizidine alkaloids, based on the highly stereoselective 1,2-addition to the CN double bond of chiral aldehyde-SAMP/RAMP hydrazones, are described. The enantioselective syntheses of the pyrrolidine alkaloids bgugaine and (2S,12¢R)-2-(12¢-aminotridecyl)-pyrrolidine, a defense alkaloid of the Mexican bean beetle are reported. Furthermore, the SAMP/RAMP-hydrazone method was applied to the syntheses of two 5,8-disubstituted indolizidine alkaloids that have been extracted from neotropical poison-dart frogs. The a-alkylation of aldehyde-SAMP/RAMP hydrazones has been used in the enantioselective synthesis of two epimers of stenusine, a 3-substituted piperidine alkaloid and spreading reagent of the beetle Stenus comma.

Renilla Bioluminescence: A Morphologic Approach to the Location of Photocytes

1974 ◽  
Vol 32 ◽  
pp. 208-209
Author(s):  
Ben O. Spurlock ◽  
Milton J. Cormier
Keyword(s):  
Excited State ◽  
Ground State ◽  
Molecular Basis ◽  
Light Emission ◽  
Chemical Basis ◽  
Electronic Excited State ◽  
Colonial Form ◽  
The Common ◽  
Eighteenth And Nineteenth Centuries ◽  
Catalyzed Oxidation

The phenomenon of bioluminescence has fascinated layman and scientist alike for many centuries. During the eighteenth and nineteenth centuries a number of observations were reported on the physiology of bioluminescence in Renilla, the common sea pansy. More recently biochemists have directed their attention to the molecular basis of luminosity in this colonial form. These studies have centered primarily on defining the chemical basis for bioluminescence and its control. It is now established that bioluminescence in Renilla arises due to the luciferase-catalyzed oxidation of luciferin. This results in the creation of a product (oxyluciferin) in an electronic excited state. The transition of oxyluciferin from its excited state to the ground state leads to light emission.

Catalytic enantioselective synthesis of indolizino[8,7-b]indole alkaloid derivatives based on the tandem reaction of tertiary enamides

2021 ◽  
Author(s):  
Xin-Ming Xu ◽  
Ming Xie ◽  
Jiazhu Li ◽  
Mei-Xiang Wang
Keyword(s):  
Indole Alkaloid ◽  
Enantioselective Synthesis ◽  
High Yield ◽  
Tandem Reaction ◽  
Indole Derivatives

An exquisite Pybox/Cu(OTf)2-catalyzed asymmetric tandem reaction of tertiary enamides was developed, which enabled the expeditious synthesis of indolizino[8,7-b]indole derivatives in high yield, excellent enantioselectivity and diastereoselectivity.

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