I am building new home through a builder who got 2.5% interested of the home. The home is building now. I wonder whether I can claim 2.5% interest the builder took.

Yes, you can deduct the interest on your construction loan if the loan was secured by the property you moved into. You can treat a home under construction as a qualified home for a period of up to 24 months, but only if it becomes your qualified home at the time it is ready for occupancy.