Photoinduced functionalization of diterpenes: photochemical behaviour of grandiflorolic acid in methanol and acetonitrile

Irradiation of grandiflorolic acid ( 11) at λ=254 nm in acetonitrile gave the two epimers 13 and 14 through a photodecarboxylation reaction of the carboxylic group on C-4. Irradiation of compound 11 in methanol at λ=254 nm provided the transformation of the C-20 angular methyl into a carbomethoxymet...

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Bibliographic Details
Published in:Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2004-03, Vol.162 (2), p.381-386
Main Authors: Buscemi, Silvestre, Rosselli, Sergio, Bruno, Maurizio, Scaglioni, Leonardo, Vivona, Nicolò, Piozzi, Franco
Format: Article
Language:English
Subjects:
Diterpenes
Grandiflorolic acid
Natural compounds
Photochemistry
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Summary:Irradiation of grandiflorolic acid ( 11) at λ=254 nm in acetonitrile gave the two epimers 13 and 14 through a photodecarboxylation reaction of the carboxylic group on C-4. Irradiation of compound 11 in methanol at λ=254 nm provided the transformation of the C-20 angular methyl into a carbomethoxymethyl group. In this case, unlike compounds 13 and 14, only one of the two possible isomers ( 15) was obtained (equatorial methyl at C-4). A mechanistic approach of this reaction in discussed, and the role of mutual stereochemistry between C-20 methyl and C-19 carboxylic group in determining the course of the reaction is pointed out.
ISSN:1010-6030
1873-2666
DOI:10.1016/S1010-6030(03)00377-0