The synthesis of diesel or jet fuels intermediates from furfural or 5-hydroxymethylfurfural (HMF) via aqueous aldol-condensation with cyclopentanone was studied. Cyclopentanone is the product of furfural rearrangement in an aqueous system. Since the aldol-condensation reaction is conducted in an aqueous solution all these biomass-derived reactants can be applied as water solutions formed in the processes of their preparation. The aldol condensation of furfural with cyclopentanone is at low concentration of base and molar ratio of reactants 2:1 highly selective and after 40-80 mm of reaction at a temperature of 40-100 C more than 95 mol% yield of 2,5-bis (2-furylmethylidene) cyclopentan-1-one (F2C) was obtained. When instead of furfural as a reactant HMF was used higher than 98 mol% yield of 2,5-bis (5-hydroxymethy1-2-furylmethylidene) cyclopentan-1-one was achieved. The final products of aldol condensation of furfural and HMF are exclusively corresponding dimers, what enables to obtain after subsequent hydrogenation/hydrodeoxygenation step dialkylcyclopentane type of diesel or jet fuels having C-15 or C-17 molecules. (C) 2014 Elsevier Ltd. All rights reserved.