Condensation of aldoses and their aldehydo derivatives with compounds of the type 1,3-cyclohexanedione. Synthesis of 2,2-aldosylidene-bis-[5-(p-hydroxyphenyl)-4,6-dicarbethoxy-1,3-cyclohexanedione] and 2,2-aldosylidene-bis-[5,5-dimethyl-1,3-cyclohexanedione] and derivatives.