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Glycosidic Linkage, Pyran, amino glycosides, Furan - Coggle Diagram

- - - - quickly attack
  - - - 產率和醇的大小成負相關
  - - - preparation: 1) Et₂NH 2) NBS, CH₃OH
      - 不喜歡形成oxacarbenium, SN2, 直接攻擊β位
- - - - if mannose, orthoester is formed;
        w/ acid, rearrangement (1-OR, 2-OH)
  - - - 1,2-trans
      - if no, then anomeric mixture
    - - 透過環境調控產生不同比例的副產物
    - - RO越鹼，越會被protonation，beta比例越多
      - 影響protonation的位置
  - - - β configuration
    - - thermodynamic product: α
    - - hydrolysis
- - - - promoter: Et₄NBr
      - leaving group: Br
        
        α-Br, then α glycosidic bond
        
        β-Br, then β glycosidic bond
      - non-participating group on O-2
    - - 2-O-alkyl
      - solvent: DCM
        
        α-configuration
        
        if ACN, β-configuration
    - - promoter: TMSOTf
- - - - unstable uber acid and high temp.
    - - stable and milder condition
    - - milder condition
    - - mild condition
      - difficult to remove
        
        modification: tetrachlorophthalimide
    - - pent-4-enoy amide
      - Troc
- - - - preparation: azidonitration of glycals, diazotransfer to 2-amino sugars
    - - hard/soft nucleophile → α/β
      - t-BuOK/DMAP → α/β
- - - - O-3/O-5 locking
      - O-2/O-3 locking