Stereo- and regioselective hydroxylation of grindelic acid derivatives by Aspergillus niger

ALEJANDRO A. ORDEN; DIEGO A. CIFUENTE; EDUARDO BORKOWSKY; CARLOS E. TONN; MARCELA KURINA SANZ

Natural Product Research

Taylor & Francis

Año: 2005 vol. 19 p. 625 - 631

1478-6419

Stereo- and regioselective hydroxylation of grindelane derivatives on position 3b was catalyzed by cultures of Aspergillus niger. Grindelic acid (1), methyl grindelate (2), 15-hydroxy-7(8)-en-9a,13(S)-oxide-ent-labdane (3) and 7a,8a-epoxymethylgrindelate (4) were bioconverted in the corresponding 3b-hydroxy derivatives as the only biotransformation products. 13(S),15-dihydroxy-8(9)-en-ent-labdane (5) remained unreacted under the same conditions. Conformational and electronic studies of the substrates are discussed.