Novel compounds are provided, which are useful as linking groups in chemical synthesis, preferably in the solid phase synthesis of oligonucleotides and polypeptides. These compounds are generally photolabile and comprise protecting groups which can be removed by photolysis to unmask a reactive group. The protecting group has the general formula Y, wherein Y is a chemical structure as shown in FIG. 1. Also provided is a method of forming, from component molecules, a plurality of compounds on a support, each compound occupying a separate predefined region of the support, using the protected compounds described above.