Pal-Glu(OSu)-OtBu is a key intermediate in the synthesis of peptide drugs, particularly for the diabetes and weight-loss drug liraglutide.

Below is a summary of its core information:

Item Information
Full Chemical Name: Nε-Palmitoyl-L-glutamic acid γ-succinimidyl α-tert-butyl ester
CAS Number: 204521-63-1
Molecular Formula: C₂₉H₅₀N₂O₇
Molecular Weight: 538.716
Primary Application Synthesis of the side-chain fragment for liraglutide

Molecular Structure and Functional Analysis
The compound's name clearly reveals its structure, which can be dissected into three functional parts:

Pal- (Palmitoyl Group): This is a long aliphatic chain composed of 16 carbon atoms. Its strong lipophilicity provides the ability for drug molecules (e.g., liraglutide) to bind to serum albumin, thereby significantly extending the drug's duration of action in the body.

Glu(OSu) (L-Glutamic Acid γ-Succinimidyl Ester): This portion constitutes the critical reactive site of the molecule. The side-chain carboxyl group (γ-position) of glutamic acid is activated as a succinimidyl ester (OSu, an NHS ester). This "active ester" is chemically reactive and can efficiently and specifically couple with amino groups on other amino acids within the peptide chain.

OtBu (α-tert-Butyl Ester): This is a protecting group. During peptide synthesis, it shields the α-carboxyl group on the glutamate backbone to prevent unwanted side reactions in certain steps. This protecting group can be removed under specific conditions (e.g., acid treatment) at a later stage of the synthesis.

Therefore, Pal-Glu(OSu)-OtBu can be regarded as a pre-assembled standard building block equipped with both a long-chain modification and a reactive "handle," facilitating its efficient and precise incorporation into the target peptide chain.

Application and Drug Context
The core value of this compound lies in its role as an essential raw material for synthesizing liraglutide. Liraglutide is a synthetic GLP-1 analog used not only to treat type 2 diabetes but also, in a higher-dose formulation, approved for obesity management. Well-known liraglutide drugs on the market include Novo Nordisk's "Victoza" and "Saxenda".

Its synthesis process is a major focus of industry research, aimed at optimizing steps, reducing costs, and enabling industrial-scale production.