Method for preparing cyclic compounds

A method for preparing a cyclic compound of Formula (3-1),

• wherein X represents CH2, O or S, n represents 0 or 1, R3 represents an alkyl group containing 1 to 6 carbon atoms, an alkenyl group containing 1 to 6 carbon atoms, a phenyl group, a heterocyclic group or a heteroylmethyl group, R4 represents an alkoxycarbonyl group containing 1 to 6 carbon atoms, a haloalkoxycarbonyl group containing 1 to 6 carbon atoms or an alkenyloxycarbonyl group containing 1 to 6 carbon atoms, and R6 represents a hydroxyalkyl group whose hydroxy moiety is protected with a protecting group, which comprises the following steps:
• a step of reacting a compound of Formula (1-1),
• wherein X, n, R3, R4 and R6 are as defined above, with a triethyl phosphite in an amount of 2 to 5 moles per mole of the compound to obtain a reaction mixture containing a compound of Formula (2-1),
• wherein X, n, R3, R4 and R6 are as defined above;
• and R5 is ethyl;
• a step of removing unreacted triethyl phosphite from the reaction mixture including reducing the internal pressure of the vessel holding the reaction mixture to 0.7 kPa or below and heating the vessel at 75° C. to 80° C. to distill off the triethyl phosphite remaining in the reaction mixture;
• and
• a step of heating the resulting mixture in a diluent.