A total synthesis of a protected form of the secoxyloganin aglucone

1989 ◽  
Vol 67 (2) ◽  
pp. 261-267 ◽  
Author(s):  
Peter T. W. Cheng ◽  
Stewart McLean
Keyword(s):  
Total Synthesis ◽  
Functional Groups ◽  
Oxidation State ◽  
Oxidative Cleavage ◽  
Enol Ether ◽  
Silyl Enol Ether ◽  
Carbon Framework ◽  
High Yields

A synthesis is described that leads from cyclopentadiene through 5-norbornen-2-one to the monosubstituted cyclopentenone 5; a vinyl substituent is attached by the reaction of a cuprate, and the enolate intermediate is trapped as the silyl enol ether 4, which is converted to 19, a product with the 10-carbon framework and stereochemistry of the secoxyloganin aglucone, and with all functional groups differentially protected and in the correct oxidation state. Explorations of the cuprate reaction required to convert the cyclopentenone 5 to the siloxycyclopentene 4 and of the reactions required for the oxidative cleavage of 4 reveal problems with these reactions when they are applied to compounds that are cyclopentane derivatives. The resolution of these problems leads to reaction sequences that proceed with high yields and excellent diastereoselectivity. Keywords: synthesis, secoxyloganin, vinyl cuprate, oxidative cleavage.

A New Enantioselective Total Synthesis of Natural Vincamineviaan IntramolecularMannichReaction of an Silyl Enol Ether

1977 ◽  
Vol 60 (5) ◽  
pp. 1801-1810 ◽  
Author(s):  
Wolfgang Oppolzer ◽  
Hartmut Hauth ◽  
Paul Pfäffli ◽  
Roland Wenger
Keyword(s):  
Total Synthesis ◽  
Enol Ether ◽  
Enantioselective Total Synthesis ◽  
Silyl Enol Ether

Total synthesis of (−)-agelastatin A: an SH2′ radical azidation strategy

2018 ◽  
Vol 54 (71) ◽  
pp. 9893-9896 ◽  
Author(s):  
Izuru Tsuchimochi ◽  
Yuta Kitamura ◽  
Hiroshi Aoyama ◽  
Shuji Akai ◽  
Keiyo Nakai ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Synthetic Approach ◽  
Enol Ether ◽  
Agelastatin A ◽  
Silyl Enol Ether ◽  
Strategic Implementation ◽  
Allylic Bromide

A new synthetic approach to (−)-agelastatin A has been established through the strategic implementation of brominative olefin transposition of a silyl enol ether and subsequent SH2′ radical azidation of the resultant allylic bromide.

Total Synthesis of (±)-Cephalosol via Silyl Enol Ether Acylation

Synthesis ◽  
2010 ◽  
Vol 2010 (06) ◽  
pp. 917-922 ◽  
Author(s):  
Ulrich Koert ◽  
Alexander Arlt
Keyword(s):  
Total Synthesis ◽  
Enol Ether ◽  
Silyl Enol Ether

scholarly journals Total synthesis of ent-pavettamine

2021 ◽  
Vol 17 ◽  
pp. 1440-1446
Author(s):  
Memory Zimuwandeyi ◽  
Manuel A Fernandes ◽  
Amanda L Rousseau ◽  
Moira L Bode
Keyword(s):  
Total Synthesis ◽  
Functional Groups ◽  
Reductive Amination ◽  
Terminal Group ◽  
Chain Extension ◽  
Protecting Group ◽  
Plant Toxin ◽  
Carbon Backbone ◽  
Naturally Occurring ◽  
Carbon Framework

Pavettamine, a plant toxin first isolated from Pavetta harborii in 1995, was previously identified as a polyamine with C2 symmetry and a 1,3-syn-diol moiety on a C10 carbon backbone – one of very few substituted polyamines to be isolated from nature. Its absolute configuration was later established by our first reported total synthesis in 2010. Herein we report the first total synthesis of the enantiomer of pavettamine, ent-pavettamine. The symmetrical structure of the molecule allows for the synthesis of a common C5 fragment that can be divergently transformed into two synthons for later convergent coupling to furnish the target carbon framework. Based on the success of the protocol we employed for the synthesis of the naturally occurring pavettamine, (S)-malic acid was again the starting material of choice for the synthesis of the two individual C5 fragments, with strategic differences in terminal-group manipulation allowing for the synthesis of ent-pavettamine rather than pavettamine. Chain extension and stereoselective ketone reduction were achieved using the (R)-methyl p-tolyl sulfoxide chiral auxiliary to give the desired 1,3-syn-diol C5 unit. A protecting-group strategy was also developed for the orthogonal protection of the alcohol and amine functional groups as they were unveiled. The functionalized C5 fragments were coupled via reductive amination revealing the C10 carbon backbone. Deprotection of the alcohol and amine functional groups successfully provided ent-pavettamine as a TFA salt.

The Gin Synthesis of Neofinaconitine

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Synthesis ◽  
Oxidative Cleavage ◽  
Diels Alder ◽  
Reductive Cyclization ◽  
Cancer Center ◽  
Enol Ether ◽  
Norditerpenoid Alkaloids ◽  
Silyl Enol Ether ◽  
Sterically Demanding ◽  
Hydrolysis Of

The hexacyclic norditerpenoid alkaloids, including neofinaconitine 4, isolated from traditional Chinese and Japanese antiarrhythmics and analgesics, have long offered a challenge to organic synthesis. The late David Y. Gin of the Memorial Sloan-Kettering Cancer Center envisioned (J. Am. Chem. Soc. 2013, 135, 14313) an approach to 4 by way of the Diels–Alder coupling of 1 and 2. This project was completed under the supervision of his colleague Derek S. Tan. The cyclopropene 6 was prepared from the ester 5. Addition of 6 to the diene derived from 7 proceeded with modest regioselectivity to give, after enol ether hydrol­ysis, the ketone 8. After two-carbon extension of the ketone with 9 to the ester 10, ionization with HBr led to 11, that was carried on the diene 1. Opening of caprolactam 12 with ethylamine followed by oxidation delivered the aldehyde 13. Acid-mediated cyclization to the enamide followed by bromination gave 14. Carbomethoxylation followed by selenylation and oxidation completed the prep­aration of the dienophile 2. With the sterically-demanding Br blocking one face of the diene, Diels–Alder cycloaddition of 2 to 1 proceeded with high diastereocontrol, leading after hydrolysis of the intermediate silyl enol ether to the ketone 15. Oxidative cleavage of the more accessible alkene followed by elimination led to the ketone 16, that on exposure to acid underwent Mannich cyclization. Oxidation followed by elimination completed the preparation of 17. Reductive cyclization to 18 established the sixth and last ring of 4, but the tertiary alcohol was lacking. This was installed by selenylation followed by oxidation, presumably by way of the transient anti-Bredt enone. There are two classes of the norditerpenoid alkaloids, having 18 and 19 carbons respectively. The ester 19 could be a versatile precursor to both classes. For 4, the carbon had to be removed. Reduction and protection followed by oxidative cleavage gave 20, that was carried on to neofinaconitine 4.

A Short Synthesis of (+)-Brefeldin C via Enantioselective Radical Hydroalkynylation

2019 ◽  
Author(s):  
Lars Gnägi ◽  
Severin Vital Martz ◽  
Daniel Meyer ◽  
Robin Marc Schärer ◽  
Philippe Renaud
Keyword(s):  
Total Synthesis ◽  
Natural Product ◽  
Oxidation State ◽  
Single Step ◽  
Radical Process ◽  
Target Molecule ◽  
Short Synthesis ◽  
The One

<div><div><div><div><p>A very concise total synthesis of (+)-brefeldin C starting from 2-furanylcyclopentene is described. This approach is based on an unprecedented enantioselective radical hydroalkynylation process to introduce the two cyclopentane stereocenters in a single step. The use of a furan substituent allows to achieve a high trans diastereoselectivity during the radical process and it contains the four carbon atoms C1–C4 of the natural product in an oxidation state closely related to the one of the target molecule. The eight-step synthesis require six product purifications and it provides (+)-brefeldin C in 18% overall yield.</p></div></div></div></div>

scholarly journals Non-Enzymatic Desymmetrization Reactions in Aqueous Media

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 720
Author(s):  
Satomi Niwayama
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Functional Groups ◽  
Organic Compounds ◽  
Recent Progress ◽  
Aqueous Media ◽  
Building Blocks ◽  
Organic Reactions ◽  
Environmentally Benign ◽  
Enzymatic Desymmetrization

Symmetric organic compounds are generally obtained inexpensively, and therefore they can be attractive building blocks for the total synthesis of various pharmaceuticals and natural products. The drawback is that discriminating the identical functional groups in the symmetric compounds is difficult. Water is the most environmentally benign and inexpensive solvent. However, successful organic reactions in water are rather limited due to the hydrophobicity of organic compounds in general. Therefore, desymmetrization reactions in aqueous media are expected to offer versatile strategies for the synthesis of a variety of significant organic compounds. This review focuses on the recent progress of desymmetrization reactions of symmetric organic compounds in aqueous media without utilizing enzymes.

Synthesis of α-Arylcarboxylic Acid Amides from Silyl Enol Ether via Migratory Amidation with 2-Azido-1,3-dimethylimidazolinium Hexafluorophosphate

2013 ◽  
Vol 42 (7) ◽  
pp. 691-693 ◽  
Author(s):  
Mitsuru Kitamura ◽  
Kento Murakami ◽  
Yuichiro Shiratake ◽  
Tatsuo Okauchi
Keyword(s):  
Enol Ether ◽  
Silyl Enol Ether
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