Remote hydroxylation of methyl groups by regioselective cyclopalladation. Partial synthesis of hyptatic acid-A.
Hyptatic acid-A (32), a 2alpha,3beta,24-trihydroxyolean-12-en-28-oic acid, previously isolated from Hyptis capitata, was obtained from maslinic acid (2). The regioselective cyclopalladation of the axial methyl group on C-4 of maslinic acid afforded the C-24 hydroxymethylene group due to the presence of a C-2-OR substituent. Nevertheless, hederagenin (7) (23-hydroxy derivative) was formed when this oxygenated group was not present.
García-Granados
Andrés
A
Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Granada, 18071, Granada, Spain.
López
Pilar E
PE
Melguizo
Enrique
E
Parra
Andrés
A
Simeó
Yolanda
Y