(+/-)-Untenone A, one of the marine cyclopentanoids, has been conveniently synthesized via (+/-)-cis-1-hexadecylcyclopent-2- en-1,4 diol 9 which has been produced from 1-hexadecylcyclopenta-1,3-diene 6 via photo-oxidation and the following reduction. The key step of the present synthesis is the selective alkylation of cyclopenta-1,3-diene to form 6. Optically active (-)- and (+)-untenone A have been prepared from (-)- and (+)-9, respectively, after enzymatic kinetic resolution of (+/-)-9. (C) 2010 Elsevier Ltd. All rights reserved.