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Synthesis 2010(1): 67-72  
DOI: 10.1055/s-0029-1217094
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Expedient Access to A-Ring-γ-Dioxygenated Terpenoids: The First Synthesis of (13E)-ent-Labda-8(17),13-diene-3β,15,18-triol

Victoriano Domingoa, Horacio R. Diégueza, Carmen P. Moralesa, Jesús F. Arteagab, José F. Quílez del Moral*a, Alejandro F. Barrero*a
a Department of Organic Chemistry, Institute of Biotechnology, University of Granada, Avda. Fuentenueva, 18071 Granada, Spain
Fax: +34(958)243318; e-Mail: afbarre@ugr.es; e-Mail: jfquilez@ugr.es;
b Department of Chemical Engineering, Physical Chemistry and Organic Chemistry, University of Huelva, Campus el Carmen, 21071 Huelva, Spain
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Publikationsverlauf

Received 24 July 2009
Publikationsdatum:
03. November 2009 (online)

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Abstract

A simple approach to A-ring-γ-dioxygenated terpenoids is described which involves two key steps, namely, selenium-catalyzed selective allylic chlorination of polyprenoids and titanocene-mediated radical cyclization of epoxypolyprenes. We have applied this synthetic route to the first synthesis of the diterpene, (13E)-ent-labda-8(17),13-diene-3β,15,18-triol. A stereoselective approach to this synthesis is also described.

Key words

diterpene - radical cyclizations - oxiranes - stereoselective synthesis - titanocene

1

Although the method described herein allows access to dihydroxyterpenes functionalized at C-3 and at the axial methyl at C-4, we use the term γ-dioxygenated terpenoids throughout the text for the sake of simplicity.

18

Since our aim here was to confirm the feasibility of our methodology for asymmetric synthesis, the enantiomeric excess was not measured. Furthermore, epoxy-alcohol 15 was obtained as a mixture of diastereoisomers.

20

No differences were found between the spectroscopic data of 15 and those of 11.