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Synthesis of Clionastatins A and B through Enhancement of Chlorination and Oxidation Levels of Testosterone.
- Source :
-
Chinese Journal of Chemistry . Dec2022, Vol. 40 Issue 23, p2747-2755. 9p. - Publication Year :
- 2022
-
Abstract
- Comprehensive Summary: A full account of semisyntheses of polychlorinated marine steroids clionastatins A and B is described. We have developed a unique two‐stage chlorination‐oxidation strategy that enabled concise and divergent semisyntheses of clionastatins A and B in 16 steps from inexpensive testosterone. Key transformations in chlorination stage include (a) conformationally controlled, stereospecific dichlorination through an unusual β‐chloronium intermediate to install the diequatorial C1,C2‐dichloride; (b) C4‐OH directed C19–H oxygenation followed by challenging neopentyl chlorination to install the C19–Cl. The high oxidation level was constructed through (a) the desaturation at C6–C7 through one‐pot photochemical dibromination–reductive debromination; (b) regioselective anti‐Markovnikov oxidation of the C6–C7 double bond by photoredox‐metal dual catalysis to forge the B ring enone; (c) late‐stage desaturation with SeO2 to introduce C8–C9 double bond. Wharton transposition was used to forge the D‐ring enone, and thermodynamically driven epimerization secured the cis‐fused C/D ring system. Furthermore, we also provided a 14‐step approach to clionastatin A by optimizing the construction of the D‐ring enone with a dehydration‐oxidation sequence. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 1001604X
- Volume :
- 40
- Issue :
- 23
- Database :
- Academic Search Index
- Journal :
- Chinese Journal of Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 160000880
- Full Text :
- https://doi.org/10.1002/cjoc.202200425