An easy and stereoselective rearrangement of an abietane diterpenoid into a bioactive microstegiol derivative

Parvifloron D was isolated from Plectranthus ecklonii together with sugiol and mixtures of beta-sitosterol and stigmasterol and ursolic and oleanolic acids. Treatment of parvifloron D [2 alpha-(4-hydroxy)benzoyloxy-11-hydroxy-5,7,9(11),13-abietatetraen-12-one] with acid-washed molecular sieves gave the microstegiol derivative 2 beta-(4-hydroxy)benzoyloxy-11 beta-hydroxy-4(5 -> 11), 20(10 -> 5)diabeo-5(10),6,8,13-abietatetraen-12-one in a moderate yield (26%). The new microstegiol derivative inhibited the growth of some Staphylococcus and Enterococcus species with significant MIC values ranging from 3.91 to 7.81 mu g/ml. (C) 2010 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.