There are two common causes why this happens to recently planted plants. The first is the plant was under shelter or inside when you bought it, and you didn't harden it off before planting it out, so frost or cold has caused the leaves to die. The second is insufficient water at the rootball, often caused by planting less than a foot away from a wall or fence. Planting too close to a wall or fence means the plant may not get sufficient water because its in the 'rain shadow' of the wall. I don't know which of these is most likely in your case.
Which variety of Jasmine is it? There's more than one which flowers in summer...