东林 Look Back to the Nomenclature IUPAC when common names are used, the letters a,B,Y,δ，etc.are often used to locate substituents 5 1 OH H2N、 OH NH2 4-Aminobutanoic acid 2-Aminopropanoic acid (Y-Aminobutyric acid; (a-Aminopropionic acid; GABA) alanine) Look Back to the Nomenclature - IUPAC ™when common names are used, the letters α, β, γ, δ, etc. are often used to locate substituents alanine) ( γ-A mi n o b utyr i c acid; ( α-A m i n o p r o pio n i c acid; GABA ) 4-A min o b u tan o i c acid 2-A min o p ro p a n oic acid 4 3 2 5 H 2 N OH O OH O NH 2 OH O α β γ δ 1