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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
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Stereocontrolled Total Synthesis of (-)-Stemaphylline
Ana Varela1, Lennart K B Garve1, Daniele Leonori2
1School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
Angewandte Chemie (International Ed. in English)
|January 19, 2017
Summary
Researchers developed a new method for synthesizing pyrrolidines using metal carbenoids and a solvent switch. This efficient process was applied to the total synthesis of (-)-stemaphylline, achieving high stereocontrol.
Area of Science:
- Organic Chemistry
- Synthetic Methodology
- Natural Product Synthesis
Background:
- Homologation of alpha-boryl pyrrolidines with metal carbenoids is synthetically challenging.
- Existing methods struggle with efficient C-C bond formation, especially with common leaving groups.
Purpose of the Study:
- To develop a novel and efficient method for the homologation of alpha-boryl pyrrolidines.
- To demonstrate the utility of this methodology in the total synthesis of a complex natural product.
Main Methods:
- A key solvent switch from diethyl ether (Et2O) to chloroform (CHCl3) was employed.
- This solvent switch facilitates an efficient 1,2-metalate rearrangement of the intermediate boronate.
- The methodology was applied to the total synthesis of the Stemona alkaloid (-)-stemaphylline.
Main Results:
- Efficient 1,2-metalate rearrangement was achieved with both halide and ester leaving groups.
- The total synthesis of (-)-stemaphylline was completed in 11 steps (longest linear sequence).
- High stereocontrol (>20:1 diastereomeric ratio) and an 11% overall yield were obtained.
Conclusions:
- The developed methodology offers an efficient route for alpha-boryl pyrrolidine homologation.
- This approach enables a streamlined total synthesis of complex molecules like (-)-stemaphylline.
- The study highlights the importance of reaction conditions, such as solvent choice, in synthetic transformations.
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