Issue 38, 2014

Approaches to the total synthesis of chaetochalasin A

Abstract

Chaetochalasin A is a complex natural product whose biosynthesis may involve two domino Diels–Alder reactions. Approaches to the total synthesis of chaetochalasin A using this approach have been studied. Methyl (6R,8S,2Z,4E,10E,12E,14E)-6,8,10,14-tetramethylhexadeca-2,4,10,12,14-pentaenoate was identified as a key intermediate and was synthesized from (E)-1-bromo-4-tert-butyldimethylsilyloxy-2-methylbut-2-ene using diastereoselective alkylations of derivatives of (+)-pseudoephedrine to introduce the stereogenic centres, a modified Julia reaction to prepare the conjugated triene and a phosphonate condensation to provide the (2Z)-alkene. However, during the synthesis, facile geometrical isomerisation of the (14E)-trisubstituted and (2Z)-double-bonds was observed and attempts to incorporate this pentaene into a synthesis of chaetochalasin A led to the formation of mixtures of products. The analogous ethyl 6,8,10,14-tetramethylhexadeca-4,10,12,14-tetraenoate [that lacks the (2Z)-double-bond] was incorporated into a Diels–Alder precursor by acylation of a valine-derived N-acylpyrrolidinone followed by oxidative elimination of the corresponding 3-(phenylselanyl)pyrrolidinone. However, preliminary studies of the macrocycle-forming Diels–Alder reaction for a synthesis of chaetochalasin A were complicated by (E,Z)-isomerisation of the (10E)-double-bond of the conjugated triene and three Diels–Alder adducts were isolated and characterised. Further studies of this approach to chaetochalasin A will require an alternative procedure for the generation of the acylpyrrolinone in the presence of the acid sensitive conjugated triene.

Graphical abstract: Approaches to the total synthesis of chaetochalasin A

Supplementary files

Article information

Article type
Paper
Submitted
24 Jun 2014
Accepted
29 Jul 2014
First published
30 Jul 2014

Org. Biomol. Chem., 2014,12, 7537-7550

Author version available

Approaches to the total synthesis of chaetochalasin A

E. J. Thomas and M. Willis, Org. Biomol. Chem., 2014, 12, 7537 DOI: 10.1039/C4OB01308E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements