CH3CH(NH2)−COOH\mathrm{CH}_{3} \mathrm{CH}\left(\mathrm{NH}_{2}\right)-\mathrm{COOH}CH3CH(NH2)−COOH
(CH3)3−COOH\left(\mathrm{CH}_{3}\right)_{3}-\mathrm{COOH}(CH3)3−COOH
NH2CH2CH2NH2\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}NH2CH2CH2NH2
