PURPOSE: To conduct the selective elimination of the protecting group from the title compound having hydroxyl groups protected with tetrahydropyranyl or silyl groups, by using a thermal condensate of a specific organotin compound with an alkyl phosphate as a catalyst.

CONSTITUTION: Using, as a catalyst, a thermal condensate from a compound selected from formulas IWIII (R is 1W12C alkyl, alkenyl, cycloalkyl, aryl, aralkyl which may be substituted; X is halogen, alkoxy, aryloxy, acyloxy, residue of partial phosphate ester; a is integer of 1W4; c=3/2 in b=1, c=1 in b=2; the compound of formula II may form a complex with the compound of formula III) and an alkyl phosphate, an organic compound containing a structural unit of the formula IV (Y is OH-protecting group such as tetrahydropyranyl or silyl), especially a compound sensitive to acid is deprotected selectively to liberate the subject hydroxyl compound in high efficiency.