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Carboxybenzyl

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Carboxybenzyl, symbol Cbz, Cbo (old symbol), or Z (in honor of its inventor Leonidas Zervas), is a carbamate which is often used as an amine protecting group in organic synthesis. It is commonly used in peptide synthesis where the carboxybenzyl protecting group is introduced by reacting the amine functionality with benzyl chloroformate in the presence of a weak base:

Contents

Alternatively, as in the Curtius rearrangement, it is made by the trapping of an isocyanate with benzyl alcohol.

It is used to protect amines from electrophiles. The protected amine can be deprotected by catalytic hydrogenation or treatment with HBr, yielding a terminal carbamic acid that then readily decarboxylates to yield the free amine.

The method was first used by Max Bergmann and Leonidas Zervas in 1932 for the synthesis of peptides. The abbreviation Z is in honor of Zervas.

Amine protection

The carboxybenzyl group (Cbz) is commonly used in organic synthesis as a protecting group for amines.

Most common amine protection methods

  • Benzyl chloroformate and a base, such as sodium carbonate in water at 0 °C
  • Benzyl chloroformate and magnesium oxide in ethyl acetate at 70 °C to reflux
  • Benzyl chloroformate, DIPEA, acetonitrile and scandium trifluoromethanesulfonate (Sc(OTf)3)
  • Most common amine deprotection methods

  • Hydrogenation in the presence of the palladium catalyst
  • References

    Carboxybenzyl Wikipedia