CC(=O)OC[C@@H](OC(C)=O)[C@H](OC(C)=O)[C@@H]1OC(C)(C)O[C@@H]1C1SCCCS1
A rotatable bond is defined as any single non-ring bond, attached to a non-terminal, non-hydrogen atom. Amide C-N bonds are not counted because of their high barrier to rotation.  How many rotatable bonds does the molecule have?