1 (555)

Prévia do material em texto

492 Chapter 26 AMINO ACIDS, PEPTIDES, PROTEINS, AND NUCLEIC ACIDS: NITROGEN-CONTAINING POLYMERS IN NATURE (c) Several ways to go, but you have to first recognize the need for a three-carbon building block with leaving groups at each end to allow linkage to both the α-carbon and (later on) the amine nitrogen to form the ring. Start with a Gabriel-type sequence. 1. NaOCH₂CH₃. 2. 3. 1 N-CH(CO₂CH₂CH₃)₂ 0 Conc. HBr (Converts OH to - Br. a good leaving group) :NH₂ + (d) Use a Gabriel-based method. Instead of forming the necessary carbon-carbon bond by SN2 reaction with a haloalkane, use an aldol-type condensation with CH₃CHO. 1. NaOCH₂CH₃ 2. NCH(CO₂CH₂CH₃)₂ HO N HOCHCH₃ (e) The extra amine group must be present in protected form. irrespective of the method used. Here's a Gabriel-type sequence. 0 Introduces the extra amine in 0 protected form.