Triethylamine (4 eq) and 4-dimethyl aminopyridine (2 eq) were added to the solution of hyaluronic acid (0.10 g, 2000 kDa) in dimethylsulfoxide (20 ml) and the mixture was stirred for 1 hour at room temperature. Then O, O' -bis (ethoxycarbonyl) adipate (2 eq, Example 4) was added to the resulting solution and the mixture was stirred at the temperature of 60 °C for 1 hour without the access of air humidity. Then the solution was cooled to room temperature, twenty times the amount of demineralized water was added and the mixture was dialyzed 7 times against 5 1 of demineralized water. The resulting solution was filtered and evaporated to yield 0.11 g of the product in form of a transparent film.