scholarly journals A new synthetic method toward a key intermediate in the total synthesis of alkannin and shikonin

2021 ◽  
pp. 174751982110116
Author(s):  
Xiaogang Zheng ◽  
Hang Hu ◽  
Defeng Xu
Keyword(s):  
Carboxylic Acid ◽  
Total Synthesis ◽  
Sodium Cyanide ◽  
Synthetic Approach ◽  
Synthetic Method

In the present work, a new synthetic method toward a key intermediate in the total synthesis of alkannin and shikonin is developed. The key intermediate, 4-methyl-1-(naphtho[1,8- de:4,5- d’e’]bis([1,3]dioxine)-4-yl)pent-3-en-1-one (5), is synthesized via the reaction of 1,8:4,5-bis(methylenedioxy)naphthalene-2-carboxylic acid N-methoxy- N-methylamide with prenyllithium. This synthetic approach avoids the use of N-methoxy- N,4-dimethylpent-3-enamide, which is not easy to obtain, and the toxic reagent sodium cyanide.

General Cyclopropane Assembly via Enantioselective Redox-Active Carbene Transfer to Aliphatic Olefins

2018 ◽  
Author(s):  
Marc Montesinos-Magraner ◽  
Matteo Costantini ◽  
Rodrigo Ramirez-Contreras ◽  
Michael E. Muratore ◽  
Magnus J. Johansson ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Asymmetric Synthesis ◽  
Chemical Space ◽  
Synthetic Approach ◽  
Asymmetric Cyclopropanation ◽  
Redox Active ◽  
Wide Range ◽  
Leaving Group ◽  
Stereoelectronic Properties ◽  
Carbene Transfer

Asymmetric cyclopropane synthesis currently requires bespoke strategies, methods, substrates and reagents, even when targeting similar compounds. This limits the speed and chemical space available for discovery campaigns. Here we introduce a practical and versatile diazocompound, and we demonstrate its performance in the first unified asymmetric synthesis of functionalized cyclopropanes. We found that the redox-active leaving group in this reagent enhances the reactivity and selectivity of geminal carbene transfer. This effect enabled the asymmetric cyclopropanation of a wide range of olefins including unactivated aliphatic alkenes, enabling the 3-step total synthesis of (–)-dictyopterene A. This unified synthetic approach delivers high enantioselectivities that are independent of the stereoelectronic properties of the functional groups transferred. Our results demonstrate that orthogonally-differentiated diazocompounds are viable and advantageous equivalents of single-carbon chirons<i>.</i>

Total syntheses and antiproliferative activities of prenostodione and its analogues

2021 ◽  
Author(s):  
Aldahir Ramos Orea ◽  
María Teresa Ramírez-Apan ◽  
Rosa M. Chávez-Santos ◽  
Rodrigo Aguayo-Ortiz ◽  
Clara I Espitia ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Total Synthesis ◽  
Indole Alkaloid ◽  
Total Syntheses ◽  
Antiproliferative Activities

A high-yielding total synthesis of the indole alkaloid prenostodione was completed in 4 steps and 44% overall yield from 1H-indole-3-carboxylic acid. The expedient syntheses of prenostodiones containing distinct substituents at...

ChemInform Abstract: Total Synthesis of the Marine Toxin Polycavernoside A (I) via Selective Macrolactonization of a Trihydroxy Carboxylic Acid.

ChemInform ◽  
2010 ◽  
Vol 32 (52) ◽  
pp. no-no
Author(s):  
James D. White ◽  
Paul R. Blakemore ◽  
Cindy C. Browder ◽  
Jian Hong ◽  
Christopher M. Lincoln ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Total Synthesis ◽  
Marine Toxin ◽  
Polycavernoside A

Synthesis of Optically Active Hydroxyalkyl Cycloheptatrienes: A Key Step in the Total Synthesis of 6,11-Methylene-LXB4

Synlett ◽  
2020 ◽  
Vol 32 (01) ◽  
pp. 45-50
Author(s):  
Udo Nubbemeyer ◽  
Analuisa Nava ◽  
Lukas Trippe ◽  
Andrea Frank ◽  
Lars Andernach ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Total Synthesis ◽  
Structure Elucidation ◽  
Butyl Ester ◽  
Optically Active ◽  
Chiral Hplc ◽  
Reaction Conditions ◽  
Acid Product ◽  
Tert Butyl ◽  
Nabh4 Reduction

AbstractStarting from methyl cycloheptatrienyl-1-carboxylate, 6-acylation was successfully achieved employing glutaryl chloride in the presence of AlCl3 under controlled reaction conditions to furnish keto carboxylic acid product. After protection of this keto carboxylic acid as tert-butyl ester, reagent-controlled enantioselective reductions delivered configuration-defined methyl-6-hydroxylalkyl cycloheptatriene-1-carboxylates with up to 80% ee. Whereas simple NaBH4 reduction of the keto carboxylic acid and subsequent lactonization afforded a methyl-6-tetrahydropyranonyl cycloheptatriene-1-carboxylate. Resolution using chiral HPLC delivered the product enantiomers with up to >99% ee Finally, ECD analyses enabled structure elucidation. The products are used as key intermediates in enantioselective 6,11-methylene-lipoxin B4 syntheses.

scholarly journals Total Syntheses of Pladienolide-Derived Spliceosome Modulators

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5938
Author(s):  
Jaehoon Sim ◽  
Eunbin Jang ◽  
Hyun Jin Kim ◽  
Hongjun Jeon
Keyword(s):  
Total Synthesis ◽  
Natural Product ◽  
Structural Features ◽  
Synthetic Approach ◽  
Synthetic Analog ◽  
Phase I Clinical Trials ◽  
Total Syntheses ◽  
Naturally Occurring ◽  
Anti Cancer ◽  
Synthetic Approaches

Pladienolides, an emerging class of naturally occurring spliceosome modulators, exhibit interesting structural features, such as highly substituted 12-membered macrocycles and epoxide-containing diene side chains. The potential of pladienolides as anti-cancer agents is confirmed by H3B-8800, a synthetic analog of this natural product class, which is currently under Phase I clinical trials. Since its isolation in 2004 and the first total synthesis in 2007, a dozen total syntheses and synthetic approaches toward the pladienolide class have been reported to date. This review focuses on the eight completed total syntheses of naturally occurring pladienolides or their synthetic analogs, in addition to a synthetic approach to the main framework of the natural product.

Analytic versus Synthetic Understanding

2019 ◽  
pp. 200-221
Author(s):  
Paul Humphreys
Keyword(s):  
Causal Factor ◽  
Synthetic Approach ◽  
Synthetic Method ◽  
Central Importance ◽  
Important Concept ◽  
Degree Of Isolation

It is argued that understanding is an epistemically more important concept than explanation. Two kinds of understanding are discussed, that based on analysis of the explanandum and a kind that is based on a synthetic method. The distinction between primary and secondary understanding shows that who is asking the why question is of central importance. A problem for causation is introduced that revolves around the degree of isolation that is needed to identify a causal factor and to distinguish causes from their carriers. It is shown that the analytic and synthetic approach can deal with partial understanding, that there can be an increase in understanding without an explanation, and that laws are not necessary for understanding.

scholarly journals Revision of the Structure and Total Synthesis of Topsentin C

Synthesis ◽  
2017 ◽  
Vol 49 (11) ◽  
pp. 2562-2574 ◽  
Author(s):  
Nikita Golantsov ◽  
Alexey Festa ◽  
Alexey Varlamov ◽  
Leonid Voskressensky
Keyword(s):  
Total Synthesis ◽  
Secondary Metabolite ◽  
Conjugate Addition ◽  
Solvent Free ◽  
Synthetic Approach ◽  
Protecting Group ◽  
Marine Alkaloids ◽  
Mild Reduction

An efficient synthetic approach to access (indol-3-yl)ethane-1,2-diamines with a protecting group at the indole N atom from readily available 3-(2-nitrovinyl)indoles is reported. This approach includes solvent-free conjugate addition of O-pivaloylhydroxylamines to 1-Boc-3-(2-nitrovinyl)indoles followed by mild reduction of the adducts. The obtained (indol-3-yl)ethane-1,2-diamines are convenient synthetic precursors for several classes of marine alkaloids. The first total synthesis of racemic topsentin C, a secondary metabolite from Hexadella sp., based on this approach is reported. The initially proposed structure for topsentin C has been revised.

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