scholarly journals Total Synthesis of Clavosolide A via Asymmetric Alcohol‐Mediated Carbonyl Allylation: Beyond Protecting Groups or Chiral Auxiliaries in Polyketide Construction

2019 ◽  
Vol 58 (31) ◽  
pp. 10718-10722 ◽  
Author(s):  
James M. Cabrera ◽  
Michael J. Krische
Keyword(s):  
Total Synthesis ◽  
Protecting Groups ◽  
Chiral Auxiliaries ◽  
Carbonyl Allylation

Chiral auxiliaries as docking/protecting groups: biohydroxylation of selected ketones with Beauveria bassiana ATCC 7159

Tetrahedron ◽  
2001 ◽  
Vol 57 (38) ◽  
pp. 8151-8157 ◽  
Author(s):  
Anna de Raadt ◽  
Barbara Fetz ◽  
Herfried Griengl ◽  
Markus Florian Klingler ◽  
Birgit Krenn ◽  
...  
Keyword(s):  
Beauveria Bassiana ◽  
Protecting Groups ◽  
Chiral Auxiliaries

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.

Zur Totalsynthese des Human-Big-Gastrins I und seines 32-Leucin-Analogons (Vorläufige Mitteilung) / Total Synthesis of Human Big Gastrin I and the 32-Leucine Analogue (Preliminary Communication)

1977 ◽  
Vol 32 (7-8) ◽  
pp. 495-506 ◽  
Author(s):  
E. Wünsch ◽  
G. Wendlberger ◽  
A. Hallett ◽  
E. Jaeger ◽  
S. Knof ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Building Blocks ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Protecting Groups ◽  
Side Chain ◽  
Tertiary Alcohols ◽  
Synthetic Product ◽  
Preliminary Communication ◽  
Final Purification

A new total synthesis of the tetratriacontapeptide amide corresponding to the proposed primary structure of human big gastrin I is described. The synthetic route was based on the preparation of six suitably protected fragments, related to sequence 28 - 34, 23 - 27, 21 - 22, 15-20, 9 - 14, and 1 - 8, to be used as building blocks for the total synthesis. The protecting groups were selected according to the Schwyzer-Wünsch strategy of maximum side chain protection based on tertiary alcohols, also for the imidazol function of histidine. Subsequent assembly of the six fragments by three different pathways using the highly efficient Wünsch-Weygand condensation procedure to ensure minimum racemization, followed by deprotection of the synthetic products via exposure to trifluoroacetic acid and final purification by ion-exchange chromatography on DEAE-Sephadex A-25 and partition chromatography on Sephadex G-25, led to human big gastrin I, homogeneous within the limits of the analytical methods used. The biological activity of the synthetic product proved to be 50 percent higher than that of human little gastrin I. The 32-leucine analogue of human big gastrin I was prepared in the same way.

scholarly journals Applications of oxazolidinones as chiral auxiliaries in the asymmetric alkylation reaction applied to total synthesis

RSC Advances ◽  
2016 ◽  
Vol 6 (36) ◽  
pp. 30498-30551 ◽  
Author(s):  
Majid M. Heravi ◽  
Vahideh Zadsirjan ◽  
Behnaz Farajpour
Keyword(s):  
Total Synthesis ◽  
Alkylation Reaction ◽  
Chiral Auxiliaries ◽  
Asymmetric Alkylation

In this review, a number of applications of chiral oxazolidinones in the asymmetric alkylation reaction applied to total synthesis are described.

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