Kinetic resolution of oxime esters with lipases — synthesis of enantiomerically enriched building blocks with quaternary carbon centers and formal total synthesis of perhydro histrionicotoxin

2002 ◽  
Vol 80 (6) ◽  
pp. 686-691 ◽  
Author(s):  
Nicole Diedrichs ◽  
Ralf Krelaus ◽  
Ina Gedrath ◽  
Bernhard Westermann
Keyword(s):  
Substrate Specificity ◽  
Total Synthesis ◽  
Solvent Effects ◽  
Kinetic Resolution ◽  
Building Blocks ◽  
Beckmann Rearrangement ◽  
Optically Active ◽  
Quaternary Carbon ◽  
Carbon Centers

Enantiomerically enriched oximes bearing stereogenic quaternary carbon centers can be obtained by lipase-catalyzed kinetic resolution of oxime esters. Substrate specificity, solvent effects, and the use of different lipases are discussed. Kinetic resolution of butyrylated oximes by lipase PS in the presence of n-butanol gave the best ee-values of both the saponified oxime and the residual oxime ester. Subsequent stereospecific Beckmann rearrangement of an enantiomerically enriched oxime provided lactams, which could be employed for the synthesis of optically active perhydro histrionicotoxin.Key words: oxime, lipase, kinetic resolution, Beckmann rearrangement, perhydro histrionicotoxin.

Synthesis of Optically Active 15-epi-9,14-Methylene Lipoxin A4

Synthesis ◽  
2018 ◽  
Vol 50 (06) ◽  
pp. 1246-1258
Author(s):  
Udo Nubbemeyer ◽  
Adile Duymaz ◽  
Jochen Körber ◽  
Carolin Hofmann ◽  
Dorothea Gerlach
Keyword(s):  
Total Synthesis ◽  
Building Block ◽  
Building Blocks ◽  
Optically Active ◽  
Protecting Groups ◽  
Lipoxin A4 ◽  
Methylene Bridge ◽  
Type Coupling ◽  
Important Field ◽  
Gain Access

The synthesis of lipoxin A4 and B4 analogues (LXA4, LXB4) to gain access to stabilized inflammation resolving compounds is an important field of research. Starting from known structural requirements of the natural compounds displaying biological activity and a broad investigation of their rapid metabolism, various LXA4 derivatives have been developed and tested. Focusing on variation and stabilization of the conjugated E,E,Z,E C7–C14 tetraene moiety of natural LXA4, a methylene bridge introduced between C9 and C14 might suppress any Z/E isomerization of the C11–C12 olefin. Intending to enable at least known structure variations in connection with the C1–C7 and the C15–C20 fragments, a convergent total synthesis starting from a known cycloheptatriene is developed. The C1–C8 building blocks are generated via six-step ex-chiral pool sequences starting from 2-deoxy-d-ribose delivering two 5,6-dihydroxy carboxylic acid derivatives with C7 aldehyde functions. The synthesis of the C8–C21 building block starts from a known cycloheptatriene 1-carbonester (C8–C14, C21) and hexanoyl chloride (C15–C20). After Friedel–Crafts-type coupling, the defined configuration of the C15 OH group is introduced via enantioselective reduction of the ketone precursor. Following an additional four steps, an aryl sulfone C9–C21 building block is completed ready for a key Julia–Kocienski olefination with the C1–C7 compounds. Finally, removal of the protecting groups completes the synthesis of the target optically active 9,14-methylene LXA4 methyl ester.

d- and l-Erythrose as sources of chiral quaternary carbon centers. Total synthesis of (−)-malyngolide and (+)-tanikolide

2003 ◽  
Vol 44 (12) ◽  
pp. 2513-2516 ◽  
Author(s):  
Alexandros E. Koumbis ◽  
Kyriaki M. Dieti ◽  
Myrofora G. Vikentiou ◽  
John K. Gallos
Keyword(s):  
Total Synthesis ◽  
Quaternary Carbon ◽  
Carbon Centers

An asymmetric synthesis of benzylic quaternary carbon centers. A formal total synthesis of (−)-mesembrine

1994 ◽  
Vol 35 (35) ◽  
pp. 6499-6502 ◽  
Author(s):  
Hideo Nemoto ◽  
Tetsuro Tanabe ◽  
Keiichiro Fukumoto
Keyword(s):  
Total Synthesis ◽  
Asymmetric Synthesis ◽  
Quaternary Carbon ◽  
Carbon Centers

scholarly journals Synthesis of Cyclohexane-Angularly-Fused Triquinanes

Synthesis ◽  
2020 ◽  
Author(s):  
Hongjun Jeon ◽  
Jeffrey D. Winkler
Keyword(s):  
Total Synthesis ◽  
Synthetic Approach ◽  
Quaternary Carbon ◽  
Carbon Centers ◽  
Naturally Occurring

AbstractCyclohexane-angularly-fused triquinanes, 6-5-5-5 tetra­cycles, have attracted the attention of synthetic chemists due to their highly congested core structures and multiple quaternary carbon centers. This review focuses on the six completed total synthesis of naturally occurring cyclohexane-angularly-fused triquinanes in addition to seven notable methodologies that have been developed for the synthesis of these structures.1 Introduction2 6-5-5-5 Tetracycles Containing a Linear Triquinane2.1 Total Synthesis of Cyclopiane Diterpenes2.2 Synthetic Approach toward Aberrarane Diterpenes2.3 Intermediates in the Total Synthesis of Magellanine-Type Alkaloids3 6-5-5-5 Tetracycles Containing an Angular Triquinane3.1 Total Synthesis of Waihoensene3.2 Miscellaneous Approaches4 Conclusion

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