This looks like a stress reaction to transplanting and/or underwatering. Sycamores are susceptible to Anthracnose (fungal disease) but we don't see symptoms of that. The most imporant thing will be to make sure the tree has adequate steady mouisture during its first two years after planting, to help the roots get established. The best way to determine when water is needed is to feel the soil (push your finger down in or dig down with a small hand tool) and if the soil is dry/warm to the touch, it's time to water again. Be careful not to overwater too! Refer to our page on Watering Trees and Shrubs for further guidance. Also, if there is mulch (which is good, to help retain soil moisture and prevent weeds) it shouldn't be more than about 3 inches deep nor should it touch directly against the trunk.

The strap placed on the tree to stabilize it also looks a  little too tight. It should be loose enough to allow for some movement of the tree. If the strap is too tight, it can restrict the flow of water and nutrients. The support strap, if even needed, shouldn't be left on longer than a year. 

Christa