Ti(III)-catalyzed cyclizations of ketoepoxypolyprenes: control over the number of rings and unexpected stereoselectivities.
We describe a new strategy to control the number of cyclization steps in bioinspired radical (poly)cyclizations involving epoxypolyenes containing keto units positioned along the polyene chain. This approach provides an unprecedentedly straightforward access to natural terpenoids with pendant unsaturated side chains. Additionally, in the case of bi- and tricyclizations, decalins with cis stereochemistry have been obtained as a consequence of the presence of the ketone. The preferential formation of cis-fused adducts was rationalized using DFT calculations. This result is completely unprecedented in biomimetic cyclizations and permits the access to natural terpenoids with this stereochemistry, as well as to non-natural analogues.
Department of Organic Chemistry and ‡Department of Inorganic Chemistry, Faculty of Sciences, University of Granada , C. U. Fuentenueva s/n, 18071 Granada, Spain.
Sara P
SP
Morcillo
Delia
D
Miguel
Sandra
S
Resa
Ana
A
Martín-Lasanta
Alba
A
Millán
Duane
D
Choquesillo-Lazarte
Juan M
JM
García-Ruiz
Antonio J
AJ
Mota
José
J
Justicia
Juan M
JM
Cuerva
D002384:Catalysis; D003500:Cyclization; D004852:Epoxy Compounds / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry; D008958:Models, Molecular; D011090:Polyenes / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism; D014025:Titanium / Q000737:chemistry*
D004852:Epoxy Compounds; D007659:Ketones; D011090:Polyenes; D014025:Titanium