PURPOSE: To provide a new compound useful as a raw material for polymers having excellent characteristics.

CONSTITUTION: A compound of formula I ((n) is 0-2; R1, R2 are H, saturated hydrocarbon; R3 is formyl, hydroxymethyl). For example, 5-hydroxymethylbicyclo [2,2,1]heptane-2,3-dicarboxylic acid. The compound of formula I is obtained by subjecting a compound of formula II, carbon monoxide and hydrogen to a hydroformylation reaction in the coexistence of a noble metal catalyst (e.g. rhodium oxide) and preferably a trisubstituted phosphine or trisubstituted phosphite in a solvent (e.g. methanol) at 60-160°C. Polymers obtained through the compound of formula I have reduced polymerization contraction and have good adhesivity to other raw materials. Good moisture absorbability and dyeability are given to the polymeric compound by the acetalation reaction of the polymeric compound.