When the secretary desires to take property comprising all or a part of the Adriaen’s Landing site and has entered into an agreement to purchase at a stipulated amount any real property with the owner or owners thereof and the amount agreed to be paid for such real property or interest is not paid within ninety days from the date when the owner or owners of such property file with the secretary a notice in writing of acceptance of such agreement, interest at four per cent per annum shall be paid on such amount by the state unless the property owner fails to furnish clear title within such ninety-day period. Such interest shall commence to accrue at the end of such ninety-day period, whether or not an assessment has been filed as provided in subsection (a) of section 32-658. Whenever the state enters into possession of real property being condemned prior to the date of execution of such an agreement, such interest shall commence to accrue from the date of actual taking of possession by the state.