1
|
Earl ADW, Li FF, Ma C, Furkert DP, Brimble MA. Stereoselective synthesis of the spirocyclic core of 13-desmethyl spirolide C using an aza-Claisen rearrangement and an exo-selective Diels-Alder cycloaddition. Org Biomol Chem 2023; 21:1222-1234. [PMID: 36633001 DOI: 10.1039/d2ob01992b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
13-Desmethyl spirolide C is a marine natural product of the cyclic imine class that demonstrates remarkable bioactivity against several biomarkers of Alzheimer's Disease, which renders its [7,6]-spirocyclic imine pharmacophore of significant synthetic interest. This work describes a facile and efficient synthesis of the [7,6]-spirocyclic core of 13-desmethyl spirolide C from inexpensive starting materials, featuring an aza-Claisen rearrangement to simultaneously set both stereocentres of the dimethyl moiety with complete atom economy, and a highly exo-selective Diels-Alder cycloaddition to construct the challenging contiguous tertiary and quaternary stereocentres of the spirocyclic core of 13-desmethyl spirolide C. A comprehensive study of the key Diels-Alder reaction was also performed to evaluate the stereoselectivity and reactivity of various functionalised dienes and protected lactam dienophiles, wherein the first successful exo-selective Diels-Alder cycloaddition to construct spirocyclic structures using a bromodiene and α-exo-methylene dienophiles is reported. This strategy not only establishes a more efficient stereoselective access to the spirocyclic core that can be used for the total synthesis of 13-desmethyl spirolide C, but also serves as a sound platform for convenient preparations of a range of spirocyclic analogues required for a comprehensive biological evaluation of this desirable pharmacophore.
Collapse
Affiliation(s)
- Andrew D W Earl
- School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1010, New Zealand.
| | - Freda F Li
- School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1010, New Zealand. .,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, 3A Symonds Street, Auckland 1010, New Zealand
| | - Chao Ma
- School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1010, New Zealand.
| | - Daniel P Furkert
- School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1010, New Zealand. .,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, 3A Symonds Street, Auckland 1010, New Zealand
| | - Margaret A Brimble
- School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland 1010, New Zealand. .,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, 3A Symonds Street, Auckland 1010, New Zealand
| |
Collapse
|
2
|
Li L, El Khoury A, Clement BO, Wu C, Harran PG. Asymmetric Organocatalysis Enables Rapid Assembly of Portimine Precursor Chains. Org Lett 2022; 24:2607-2612. [PMID: 35377667 DOI: 10.1021/acs.orglett.2c00556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sequential organocatalytic additions of 2-furanone and dihydroxyacetone derivatives to a crotonaldehyde lynchpin provide polyhydroxylated chains reminiscent of lactonized deoxo Kdn type sugars. Further homologation via Kulinkovich ring opening of the butyrolactone and acylation of the zinc homoenolate derived from the incipient cyclopropanol allows assembly of functionalized chain precursors to portimine. Our experiments probe the stability and reactivity of monosubstituted methylidene pyrrolines and generate advanced intermediates useful for exploring the biosynthesis and de novo synthesis of portimine.
Collapse
Affiliation(s)
- Liubo Li
- Department of Chemistry and Biochemistry, University of California-Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States
| | - Anton El Khoury
- Department of Chemistry and Biochemistry, University of California-Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States
| | - Brennan O'Neil Clement
- Department of Chemistry and Biochemistry, University of California-Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States
| | - Carolyn Wu
- Department of Chemistry and Biochemistry, University of California-Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States
| | - Patrick G Harran
- Department of Chemistry and Biochemistry, University of California-Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States
| |
Collapse
|