A new synthesis of castasterone and brassinolide from stigmasterol. A concise and stereoselective elaboration of the side chain from a C-22 aldehyde

Brassinolide ( 1 ) and castasterone ( 2 ) were prepared from aldehyde 7 , in turn available from stigmasterol ( 3 ). The addition of (E)-1-propenyllithium to 7 , followed by diastereoselective Sharpless epoxidation of allylic alcohol 8 using ( L )-(+)-diethyl tartrate, and regioselective epoxide-ope...

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Bibliographic Details
Published in:Canadian journal of chemistry 1993-02, Vol.71 (2), p.156-163
Main Authors: Back, Thomas G, Blazecka, Peter G, Krishna, M. Vijaya
Format: Article
Language:English
Subjects:
Alicyclic compounds, terpenoids, prostaglandins, steroids
Chemistry
Exact sciences and technology
Organic chemistry
Preparations and properties
Steroids
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Summary:Brassinolide ( 1 ) and castasterone ( 2 ) were prepared from aldehyde 7 , in turn available from stigmasterol ( 3 ). The addition of (E)-1-propenyllithium to 7 , followed by diastereoselective Sharpless epoxidation of allylic alcohol 8 using ( L )-(+)-diethyl tartrate, and regioselective epoxide-opening of (threo) epoxy alcohol 15 with isopropylmagnesium chloride in the presence of a catalytic amount of cuprous cyanide afforded diol 17 . The epoxidation and cuprate addition steps were investigated in greater detail with the simpler model aldehyde 4 . Hydrolysis of 17 provided 2 , which was converted preferentially into 1 or its regioisomer 22 by Baeyer-Villiger oxidation with trifluoroperoxyacetic acid or peroxyseleninic acids, respectively.
ISSN:0008-4042
1480-3291
DOI:10.1139/v93-022