- CH3−CH(NH2)−COOHCH3−CH(NH2)−COOHC H_{3}-C H\left(N H_{2}\right)-C O O H
- H2N−CH2−COOHH_{2} N-C H_{2}-C O O H
- H2N−CH2−CH2−COOHH_{2} N-C H_{2}-C H_{2}-C O O H
- CH3−CH2−CH(NH2)−COOHC H_{3}-C H_{2}-C H\left(N H_{2}\right)-C O O H