REGIO- AND STEREOSELECTIVE HYDROXYLATION OF GRINDELIC ACID AND ITS 3α-HYDROXY DERIVATIVE

Abstract

A hydrocyl group was selectively introduced at the C-17 or C-6 position of grindelic acid (1a) and 3α-hydroxygrindelic acid (1b) via the 17- or 7β-bromo derivatives (6a, b or 9a, b) given respectively by bromination with Br₂ or NBA. The 7β-hydroxy derivatives (17a, b) were obtained via the 8β-methyl-7-one derivatives (14a, b) by reduction with NaBH₄. The 7α-hydroxy derivatives (18a, b) were obtained selectively from the 8, 9-en-7-one derivatives (15a, b) which contain a cleaved structure at the C-9 position.