Yes , you are not eligible for 80 C deduction since
Principal u/s 80C
Payment for the purposes of purchase or construction of a residential house property the income from which is chargeable to tax under the head "Income from house property" towards repayment of the amount borrowed by the assessee . In order to claim deduction the property should be taxable under Income from house property. An asset under construction is not chargeable under this head, therefore till construction is completed principal payment cannot be deducted u/s 80C
Interest - u/s 24
Where the property has been acquired or constructed with borrowed capital, the interest, if any, payable on such capital borrowed for the period prior to the previous year in which the property has been acquired or constructed, shall be deducted under this clause in equal instalments for the said previous year and for each of the four immediately succeeding previous years - Therefore for Interest there is a precondition that construction should be completed for claiming deduction of interest