The present invention has an object to develop novel compounds which are effective for the therapy of syndrome X, cancer, myxedema, vascular chronic inflammation and the like, and furthermore prevent/treat the restenosis caused in an artery expansion by a balloon or a stent and have the activity facilitating regenerative medicine by inhibiting rejection of own cells or tissues to be transplanted and the method for preparing the same. Novel acetal derivatives obtained by acylating the hydroxyl group at the 2-position of the orcylaldehyde which ascochlorin and its analogs have and thereafter bonding an alcohol to the aldehyde group in the presence of a basic catalyst are found to achieve the object.