Tax exemption on property sale - section 54

I purchased an apartment in Lucknow in the year 2000 - first purchase, direct from the builder. The property was purchased under an Unregistered Sale Agreement (with Letter of Allotment, etc.). I now propose to sell this property, and reinvest the proceeds in a new property in Lucknow. Will I be able to claim capital gains exemption under Section 54 of the Income Tax Act on the sale of the first property? Or will the exemption be denied because the property was not purchased under a registered sale deed?