Irradiation of grandiflorolic acid (11) at 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 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.
|Titolo:||Photoinduced functionalization of diterpenes : photochemical behaviour of grandiflorolic acid in methanol and acetonitrile|
|Parole Chiave:||Diterpenes; Grandiflorolic acid; Natural compounds; Photochemistry|
|Settore Scientifico Disciplinare:||Settore CHIM/06 - Chimica Organica|
|Data di pubblicazione:||2004|
|Digital Object Identifier (DOI):||10.1016/s1010-6030(03)00377-0|
|Appare nelle tipologie:||01 - Articolo su periodico|