thus obtained the system is maintained under stirring and 4 eq of boc 2 o 14 mg dissolved in ch 2 cl 2 are added drop wise the system is left under stirring for 18 hours at room temperature the product is then precipitated by mtbe in an ice bath filtered through a gooch 3g crucible washed with et 2 o and recrystallised from etoh the 1 h nmr spectrum of the compound is given in fig3 tab 3 20 mg of peg derivative are dissolved in meoh in a three neck 50 ml flask and pd oh 2 is added as catalyst in a quantity equal to 20 by weight on the substrate the system is left under stirring overnight under h 2 atmosphere and room temperature at the reaction end after removing the catalyst via filtration through a pleated filter the meoh is removed under reduced pressure the solid obtained is re dissolved in accn and then precipitated by mtbe in a ice bath filtered through a gooch 3g crucible washed with et 2 o and stored over koh the 1 h nmr spectrum of the compound is given in fig4 tab 4 the bifunctional peg derivatives of the invention can be usefully employed for carrier and or stabilizer applications by conjugation with biologically active molecules for the purposes of non limiting illustration the following example presents the conjugation of a bifunctional peg obtained as previously described with two different amino acids 250 mg 0 039 mmol of z u2014 nh u2014 co u2014 o u2014 peg u2014 nh 2 fig6 h nmr spectrum tab 5 are coevaporated with anhydrous ch 2 cl 2 u00d7 2 and left to dry using a rotary pump after dissolving the peg derivative in a mixture of solvents 1.