Abstract Polyenyl derivatives of permethylated 6-amino-6-deoxy-β-cyclodextrin were obtained by polycondensation of acetaldehyde on permethylated 6-amino-6-deoxy-β-cyclodextrin. The acetaldehyde was provided by enzymatic hydrolysis of vinyl laurate or used directly. The mechanism of this polycondensation reaction between an acetaldehyde and modified cyclodextrins is discussed. The immobilised lipase of Mucor miehei appeared to increase the rate of this unexpected reaction, as well as permethylated 6-amino-6-deoxy-β-cyclodextrin for the water uptake to form the enamine. This polymerisation-type reaction was optimised to obtain a permethylated 6- N-decapentaenyl-6-deoxy-β-cyclodextrin as the main product.