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.

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.

Thieme Chemistry Journals Awardees – Where Are They Now? ­Ribosylation of an Acid-Labile Glycosyl Acceptor as a Potential Key Step for the Synthesis of Nucleoside Antibiotics

Synlett ◽  
2017 ◽  
Vol 29 (04) ◽  
pp. 440-446 ◽  
Author(s):  
Christian Ducho ◽  
Daniel Wiegmann ◽  
Anatol Spork ◽  
Giuliana Niro
Keyword(s):  
Total Synthesis ◽  
Antibacterial Agents ◽  
Protecting Group ◽  
Nucleoside Antibiotics ◽  
Naturally Occurring ◽  
Efficient Construction ◽  
Pentenyl Glycosides ◽  
Acid Labile

Naturally occurring nucleoside antibiotics (e.g., muraymycins and caprazamycins) represent attractive lead structures for the development of urgently needed novel antibacterial agents. One major challenge in the total synthesis of muraymycins, caprazamycins, and their analogues is the efficient construction of the densely functionalized aminoribosylated uridine-derived core unit. In order to avoid tedious protecting-group manipulations, we have aimed to conduct the aminoribosylation step with an acid-labile glycosyl acceptor. Therefore, different glycosylation approaches have been studied, with pentenyl glycosides giving the best results.

Short Protecting Group-free Syntheses of CDE Synthon of Racemic Camptothecin

2020 ◽  
Vol 17 (7) ◽  
pp. 588-591
Author(s):  
Pingxuan Shao ◽  
Wei Lu ◽  
Lei Wang
Keyword(s):  
Total Synthesis ◽  
Future Development ◽  
Protecting Group ◽  
Short Route ◽  
The Future ◽  
Tricyclic Ketone

A practical and concise total synthesis of tricyclic ketone 7 (CDE ring), a valuable intermediate for the synthesis of racemic camptothecin and analogs, was described (8 chemical steps and 29% overall yield). The synthesis starts with two inexpensive, readily available materials and is operationally simple to perform. It is worth mentioning that the reported protecting group-free synthesis, with advantages of a short route, would be helpful for the future development of industry-scale syntheses of camptothecin-family alkaloids.

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.

scholarly journals Oxazolidinones as Chiral Auxiliaries in the Asymmetric 1,4-Conjugate Addition Reaction Applied to the Total Synthesis of Natural Products: A Supplemental Mini-Review

2018 ◽  
Vol 15 (1) ◽  
pp. 3-20 ◽  
Author(s):  
Vahideh Zadsirjan ◽  
Majid M. Heravi
Keyword(s):  
Total Synthesis ◽  
Biological Activities ◽  
Conjugate Addition ◽  
Chiral Auxiliary ◽  
Addition Reactions ◽  
Chiral Auxiliaries ◽  
Complex Molecules ◽  
Total Syntheses ◽  
Naturally Occurring ◽  
Wide Range

Background: The most frequently used chiral auxiliaries, oxazolidinones (Evans' oxazolidinones) have been employed in 1,4-congugate addition reactions to α,β-unsaturated carbonyl compounds. Supplementary to our previous reports in this mini-review, we attempted to underscore the applications of this strategy in a step (steps) in the total synthesis of some naturally occurring compounds exhibiting diverse biological activities. Objective: In this mini-review, we try to underscore the applications of oxazolidinones (Evans’ oxazolidinones) in 1,4-congugate addition reactions to α,β-unsaturated carbonyl in the total synthesis of some naturally occurring compounds exhibiting diverse biological activities. Conclusion: In spite of well-known superiority of asymmetric catalyzed reactions, the use of auxiliarycontrolled reactions are still considered as commanding, vital and sometimes as only tools in the generation of stereogenic centers during the construction of complex molecules and total synthesis of naturally occurring compounds. The commercial availability, or readily accessibility of a wide variety of chiral amino alcohols as starting materials to synthesize a wide range of oxazolidinones is the merits of them. In addition, the ease of removal and subjection to various and diverse stereoselective reactions make oxazolidinones as the ideal and superior chiral auxiliaries. In this regard, they were successfully used in asymmetric 1,4-conjugate addition reactions with high stereoselectivities. The high degree of asymmetric induction can be attributed to the rigid chelation of N-acyloxazolidinones with metal ions, as well as the covering of one face of the system by the bulkiness of 4-substituent. In summary, in this report, the importance of the applications of chiral oxazolidinones as suitable chiral auxiliaries in the stereoselective, 1,4-conjugate addition reactions in asymmetric synthesis and in particular, the total synthesis of naturally occurring compounds and some complex molecules were underscored. Noticeably, in these total syntheses, this chiral auxiliary is controlling the stereochemistry of a newly created stereogenic center as well as preserving the configuration of other chiral centers, which already have been presented in the precursor. General methods have been established for the attachment of the chiral auxiliary as a moiety to the substrate molecule in high to excellent yields. At the end of these reactions, this auxiliary can be easily removed leaving various desired reactive motifs for the next step in multi-step synthesis.

ChemInform Abstract: Total Synthesis and Determination of the Absolute Configuration of FD-838, a Naturally Occurring Azaspirobicyclic Product.

ChemInform ◽  
2009 ◽  
Vol 40 (47) ◽  
Author(s):  
Yujiro Hayashi ◽  
Kuppusamy Sankar ◽  
Hayato Ishikawa ◽  
Yuriko Nozawa ◽  
Kazutoshi Mizoue ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Absolute Configuration ◽  
Naturally Occurring ◽  
The Absolute
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