  In the context of FRW spacetime with zero spatial curvature, we consider a
multi-scalar tensor cosmology model under the pretext of obtaining quadratic
conservation laws. We propose two new interaction potentials of the scalar
field. Integral to this task, is the existence of dynamical Noether symmetries
which are Lie-B\"{a}cklund transformations of the physical system. Finally,
analytical solutions of the field are found corresponding to each new model. In
one of the models, we find that the scale factor mimics $\Lambda$-cosmology in
a special case.
