−OCOCH3-OCOCH_{3}−OCOCH3
−NHCOCH3-\mathrm{NHCOCH}_{3}−NHCOCH3
−COOCH2CH3-\mathrm{COOCH}_{2} \mathrm{CH}_{3}−COOCH2CH3
−SO2NH2-\mathrm{SO}_{2} \mathrm{NH}_{2}−SO2NH2