TY - JOUR
T1 - Rhodium catalyzed hydroformylation of kaurane derivatives: A route to new diterpenes with potential bioactivity
AU - Peixoto, Andreia F.
AU - de Melo, Daniela S.
AU - Fernandes, Tânia F.
AU - Fonseca, Yuraima
AU - Gusevskaya, Elena V.
AU - Silva, Artur M.S.
AU - Contreras, Ricardo R.
AU - Reyes, Marisela
AU - Usubillaga, Alfredo
AU - dos Santos, Eduardo N.
AU - Pereira, Mariette M.
AU - Bayón, J. Carles
PY - 2008/6/1
Y1 - 2008/6/1
N2 - Kaurenic and grandiflorenic acids are naturally occurring diterpenes whose biological activity has been described. Both acids contain an exocyclic methylenic double bond that allows further functionalization on their structure. In an attempt to expand the number of derivatives of these two natural products, we have undertaken a study on the hydroformylation of the methyl esters of the two acids and the trimethylsilyl ether of kaurenol. These substrates have been hydroformylated by using unmodified Rh catalysts, as well as Rh/PPh3 and Rh/tris-(o-t-butylphenyl)phosphite catalytic systems at 100 °C and 20 bar of CO/H2 (1:1). For the three substrates, the two Rh catalysts modified with P-donor ligands, produced high conversions and chemo- and regioselectivities in the diastereoisomeric pair of linear aldehydes. In all cases, the stereoselectivity observed is strongly dependent of the system used, being the most diastereoselective the least hindered unmodified Rh/CO catalyst. A correlation between the higher diastereoselectivity and the faster β-elimination of the metal-alkyl intermediate observed in the unmodified system is discussed. © 2008 Elsevier B.V. All rights reserved.
AB - Kaurenic and grandiflorenic acids are naturally occurring diterpenes whose biological activity has been described. Both acids contain an exocyclic methylenic double bond that allows further functionalization on their structure. In an attempt to expand the number of derivatives of these two natural products, we have undertaken a study on the hydroformylation of the methyl esters of the two acids and the trimethylsilyl ether of kaurenol. These substrates have been hydroformylated by using unmodified Rh catalysts, as well as Rh/PPh3 and Rh/tris-(o-t-butylphenyl)phosphite catalytic systems at 100 °C and 20 bar of CO/H2 (1:1). For the three substrates, the two Rh catalysts modified with P-donor ligands, produced high conversions and chemo- and regioselectivities in the diastereoisomeric pair of linear aldehydes. In all cases, the stereoselectivity observed is strongly dependent of the system used, being the most diastereoselective the least hindered unmodified Rh/CO catalyst. A correlation between the higher diastereoselectivity and the faster β-elimination of the metal-alkyl intermediate observed in the unmodified system is discussed. © 2008 Elsevier B.V. All rights reserved.
KW - Diterpenes
KW - Hydroformylation
KW - Kauranes
KW - Phosphine
KW - Phosphite
KW - Rhodium
U2 - 10.1016/j.apcata.2008.02.015
DO - 10.1016/j.apcata.2008.02.015
M3 - Article
SN - 0926-860X
VL - 340
SP - 212
EP - 219
JO - Applied Catalysis A: General
JF - Applied Catalysis A: General
IS - 2
ER -