"A practical supplier guide to Di-tert-butyl dicarbonate (CAS 24424-99-5, Boc anhydride, (Boc)2O): what the reagent is (C10H18O5, MW 218.25, EINECS 246-240-1, white low-melting solid, mp ~23 C, store 2-8 C), why the Boc protecting group is the backbone of peptide and amino-acid synthesis, where it is used beyond peptides as a carboxylation/acylation reagent, moisture-sensitive handling and storage notes, what to check when buying, and how it pairs with peptide actives such as GHK-Cu and Argireline and with ketone intermediates like acetophenone."
-Deshangchemical-chemechemi
Di-tert-butyl Dicarbonate (CAS 24424-99-5): The Quiet Reagent Behind Every Protected Peptide
Di-tert-butyl dicarbonate, better known as Boc anhydride or (Boc)&sub2;O, is one of those reagents that rarely makes the headlines but shows up in almost every peptide-synthesis lab and API pilot plant. If you buy a cosmetic peptide, an amino-acid derivative, or a small-molecule drug that carries a protected amine, the odds are good that a Boc group was involved somewhere in the route. At CAS 24424-99-5, molecular formula C10H18O5, molecular weight 218.25, it is a white, low-melting solid that does one job extremely well: it puts a tert-butoxycarbonyl (Boc) group onto an amine, and takes it off again when you are ready.
| Property | Value |
|---|---|
| CAS Number | 24424-99-5 |
| Synonyms | Di-tert-butyl dicarbonate; Boc anhydride; (Boc)&sub2;O; tert-butyldicarbonate; pyrocarbonic acid di-tert-butyl ester |
| Molecular Formula | C10H18O5 |
| Molecular Weight | 218.25 |
| EINECS | 246-240-1 |
| Appearance | White powder (low-melting solid, mp ~23 °C) |
| Melting Point | 23 °C (lit.) |
| Boiling Point | 56–57 °C / 0.5 mmHg (lit.) |
| Density | 0.95 g/mL at 25 °C (lit.) |
| Storage | 2–8 °C, sealed, dry |
| Category | Amino Protecting Reagent; Peptide Synthesis; Pharmaceutical Intermediate; Carboxylation Reagent |
Why formulators and process chemists keep it on the shelf
The Boc group is a cornerstone of amine protection in both solution-phase and solid-phase peptide synthesis. Amino acids cannot simply be coupled to build a chain — the side-chain and terminal amines would react where you do not want them to. Boc anhydride cleanly converts a free amine into a carbamate that survives most coupling and deprotection conditions used for the rest of the chain, then is removed under mildly acidic conditions (typically TFA or HCl in dioxane) without touching the peptide backbone. That selectivity is exactly why it remains a default choice even as newer protecting strategies have appeared.
Beyond peptides: a general acylation and carboxylation reagent
Although peptide work is the headline application, Boc anhydride is also a general carboxylation and acylation reagent. It is used to prepare protected amino acids, to install Boc groups on heterocyclic amines in pharmaceutical-intermediate synthesis, and as a carbonyl source in certain organic transformations. In the product families we supply, you can see the same logic at work: the bioactive peptides such as GHK-Cu copper peptide and Argireline (Acetyl Hexapeptide-8) are precisely the kind of molecules whose industrial routes depend on reliable amine protection, and creatine monohydrate, a guanidino compound, sits in the same broad amino-acid-derivative space where protecting-group chemistry is routine.
Handling: keep the water out
Boc anhydride melts around 23 °C and has a reported boiling point of 56–57 °C at 0.5 mmHg, with a density near 0.95 g/mL. Those numbers tell you two practical things. First, it is a low-melting solid — in a warm warehouse it can arrive as a semiliquid, which is normal and not a defect. Second, and more important, it hydrolyzes on contact with water to tert-butanol and CO&sub2;. That makes moisture control the single biggest factor in shelf life. We recommend cold storage at 2–8 °C, tight resealing after each use, and keeping the container under dry air or nitrogen when practical. Material left open in a humid room will lose assay and may pressurize slightly as CO&sub2; evolves.
What to look for when you buy
When you source Boc anhydride, the spec that matters most is assay, followed by free acid and moisture. A high-purity grade (typically ≥99%) gives cleaner couplings and less side-product cleanup downstream, which pays for itself in peptide and API work where purification is expensive. Color should be white to off-white; a yellowing batch usually signals partial hydrolysis. For customers scaling from lab to plant, consistency between lots — same assay, same residual-solvent profile — is often more valuable than a slightly lower price.
Sits naturally alongside other building-block intermediates
Boc anhydride pairs well with the other intermediates we stock. Aromatic ketones such as 4'-methylpropiophenone and 4'-ethylpropiophenone, and the parent acetophenone, are the kind of electrophilic building blocks that combine with protected amines in multi-step syntheses. Having a single supplier cover both the protecting reagent and the ketone intermediates simplifies qualification and logistics.
The bottom line
In short, Boc anhydride is unglamorous but indispensable. It is the reagent that lets a chemist build a peptide one residue at a time, protect an amine through a hostile sequence of reactions, and then remove the guard cleanly when the molecule is finished. For labs and factories working with peptides, protected amino acids, or amine-bearing pharmaceutical intermediates, a reliable, high-purity, well-stored supply of CAS 24424-99-5 is not a luxury — it is part of the baseline.
Quick Q&A
Q: Is Boc anhydride the same as (Boc)&sub2;O?
A: Yes. Boc anhydride, di-tert-butyl dicarbonate, and (Boc)&sub2;O are the same compound, CAS 24424-99-5.
Q: How should it be stored?
A: Cold, 2–8 °C, tightly sealed, away from moisture. It hydrolyzes to tert-butanol and CO&sub2; on contact with water.
Q: What is a typical use level?
A: Usage is stoichiometric and reaction-specific. Process chemists normally calculate it per mole of amine to be protected, often with a slight excess, under anhydrous conditions.
