organic solvent results in hydrolysis of the protecting group p and the acetonide spontaneous intramolecular ketalization yields the spiroketal derivatives iv suitable acid catalysts include hydrogen chloride hydrogen bromide methane sulfonic acid sulfuric acid fluoboric acid and the like preferred is fluoboric acid suitable organic solvents include toluene tetrahydrofuran ether glyme lower alcohols and the like water concentration may be from 0 1 to 20 preferably 0 5 to 10 based on volume acid concentrations may be from 0 05n to 3 0n preferably 0 1n to 1n based on total solution volume step 3 the sulfonate ester v is prepared by reaction of iv with a sulfonyl chloride for example p toluenesulfonyl chloride in pyridine at 30 u00b0 c to 30 u00b0 c preferably 15 u00b0 c to 10 u00b0 c step 4 the nitrile vi is obtained from the sulfonate ester v by reaction with an alkali metal cyanide salt e g potassium or sodium cyanide the reaction is conducted in a suitable solvent such as acetone acetonitrile dimethylformamide or dimethylsulfoxide at 0 u00b0 to 100 u00b0 preferably 25 u00b0 c to 90 u00b0 c step 5 reaction of vi with r 3 x when r 3 is other than hydrogen is achieved in a.