1: 2,4-dioxo-5-[(p-hydroxyphenyl)-methyl]thiazolidine With sodium hydride in N,N-dimethyl-formamide T=20°C; Metallation; 2 h; 2: 2-(1,3-dioxa-2-cyclopentyl)-ethyl bromide in N,N-dimethyl-formamide T=50°C; Condensation; 5 h; Further stages.;