A novel class of beta-cyclodextrins (beta-CDs) bearing alkyl chains on the secondary face and poly(ethylene oxide) chains on the primary face was synthesized. Their interactions with two water-soluble derivatives of triphenylphosphane were investigated by P-31{H-1} and H-1 NMR. Their behaviour in rhodium-catalysed biphasic hydroformylation of 1-decene was evaluated and the best result was obtained with a beta-CD bearing methyl groups on the secondary face and poly(ethylene oxide) chains on the primary face. This CD appeared to be more efficient than randomly methylated beta-CD which is Currently one of the best mass transfer additives for hydroformylation. (C) 2009 Elsevier B.V. All rights reserved.