H3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an active and environmentally friendly catalyst for the liquid-phase conversion of beta-caryophyllene (1) to beta-caryolanyl acetate (2) in homogeneous and heterogeneous systems. An efficient and clean method for the synthesis of 2, providing a mixture containing two stereoisomeric beta-caryolanyl acetates 2a and 2b, 2a/2b = 80/20 mol/mol, with 100% GC yield, has been developed using PW as a homogeneous catalyst under mild reaction conditions. The reaction occurs at 25 degrees C with a catalyst turnover number of 2000. The catalyst can be recovered without neutralization and reused without loss of activity and selectivity. (c) 2009 Elsevier B.V. All rights reserved.