Optically active 1,1,2-trifluoro- or 1,2-difluoroallylic alcohols were prepared via a lipase-catalyzed reaction and their absolute configuration was determined by an X-ray crystallographic analysis of the corresponding ferrocene ester along with the refined Mosher method (the Kusumi-Ohtani method). (C) 2000 Elsevier Science Ltd. All rights reserved.