Synthesis of monoprotected derivatives of homo-bifunctional molecules

Selective derivatization of one of the two functional groups in a symmetrical homo-bifunctional molecule is always an uphill synthetic task. A novel method for synthesis of mono-protected homo-bifunctional poly(ethylene glycol) (PEG) is described in this work. The methodology utilizes a combination of two protecting groups that are orthogonal to each other for the introduction of one of these groups into symmetrical homo-bifunctional PEG polymers. Different well-known protecting groups, namely the carbobenzyloxy (Z) and the t-butyloxycarbonyl (Boc) groups, have been evaluated for this particular purpose. The approach appears to be straightforward in terms of separation of desired products from other non-desirable products or reactants. The methodology described here might be applicable to any symmetrical homo-bifunctional molecular substance and for synthesis of its corresponding monoprotected derivatives.