4-Methoxycarbonylcubanecarboxylic acid
[CAS 24539-28-4]

Identification

• Classification: Organic raw materials >> Carboxylic compounds and derivatives
• Name: 4-Methoxycarbonylcubanecarboxylic acid
• Molecular Formula: C₁₁H₁₀O₄
• Molecular Weight: 206.19
• CAS Registry Number: 24539-28-4
• EC Number: 691-562-1
• SMILES: COC(=O)C12C3C4C1C5C2C3C45C(=O)O

Properties

• Density: 2.0±0.1 g/cm³ Calc.^*
• Boiling point: 341.5±42.0 °C 760 mmHg (Calc.)^*
• Flash point: 141.4±21.4 °C (Calc.)^*
• Index of refraction: 1.822 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P264-P264+P265-P271-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Eye irritation	Eye Irrit.	2A	H319

chemBlink Chemical Story

4-(Methoxycarbonyl)cubane-1-carboxylic acid brings an almost diagrammatic shape into practical organic chemistry. Its central cage places eight carbon atoms at the corners of a cube, joined along the edges. Two opposite cage positions carry carbonyl-containing substituents: one is a free carboxylic acid and the other is a methyl ester. The molecule therefore combines a rigid three-dimensional framework with two related but chemically distinguishable handles. It is a functionalized building block, not simply the parent hydrocarbon cubane.

That distinction explains much of its usefulness. A free acid can be activated for coupling while a methyl ester is retained for a later transformation, provided the chosen conditions are compatible. The two groups need not be modified at the same time. This differentiated design provides a way to connect one end of the cage to a partner while preserving another point for further elaboration. It also explains why the monoacid-monoester must be distinguished from both cubane-1,4-dicarboxylic acid and its dimethyl ester: similar names conceal different possibilities for controlling a sequence.

The cage itself invites comparison with more familiar molecular shapes. Benzene is flat and aromatic; cubane is a saturated carbon cage. Opposite substituents on a cubane can provide an alternative spatial arrangement to substituents across a benzene ring, which has encouraged investigation of cubane as a benzene bioisostere. A bioisostere is a replacement considered for its ability to preserve useful properties in a particular molecular setting. The term describes a design hypothesis to test, not a guarantee that two fragments have identical electronic behavior or biological effects.

This wider idea received experimental support in a 2016 study by Chalmers and colleagues. They prepared and evaluated cubane analogues of several biologically active molecules, obtaining outcomes that depended on the molecule being modified. The relevance to a reagent such as this monoacid-monoester is contextual: functionalized cages give researchers ways to build and compare new structures. The biological results of those completed analogues cannot be assigned to the unelaborated building block, and a promising scaffold replacement in one series does not ensure success in another.

The free acid also opens a less obvious pathway. Sigma-Aldrich identifies this specific compound as a substrate for iododecarboxylation using an N-iodoamide under irradiation. In such a transformation, the carboxyl group supplies a route to a carbon-iodine connection through loss of carbon dioxide. The 2011 method paper describes a broader metal-free approach to converting carboxylic acids into organic iodides. For the cubane reagent, this provides a documented example of treating the acid as a transformable handle rather than merely as a permanent attachment group.

The enduring interest of the molecule lies in the combination of shape and differentiation. A drawing of a cube alone says little about how a useful target can be assembled. A cube carrying one free acid and one protected acid offers an ordered way forward, allowing the two ends to play different roles. Whether the goal is a new synthetic intermediate or an analogue for biological testing, the final result still requires characterization and evaluation. The reagent's contribution is to make a distinctive carbon framework accessible for those experiments without confusing the potential of the cage with a demonstrated property of every compound that contains it.

Even its two carbonyl groups have different immediate roles. One includes an acidic hydroxyl group, while the other includes a methoxy group. Reading that small distinction correctly is what turns an appealing cage drawing into a usable reaction plan, and prevents accidental substitution of the diacid or diester.

References:
1. Sigma-Aldrich. 4-Methoxycarbonylcubanecarboxylic acid, 901001; identity and iododecarboxylation application. https://www.sigmaaldrich.com/US/en/product/aldrich/901001
2. Kulbitski K et al. Metal-Free Efficient, General and Facile Iododecarboxylation Method with Biodegradable Co-Products. Adv Synth Catal. 2011;353:1438-1442. DOI: 10.1002/adsc.201100145. https://advanced.onlinelibrary.wiley.com/doi/abs/10.1002/adsc.201100145
3. Chalmers BA et al. Validating Eaton's Hypothesis: Cubane as a Benzene Bioisostere. Angew Chem Int Ed. 2016;55:3580-3585. DOI: 10.1002/anie.201510675. https://pubmed.ncbi.nlm.nih.gov/26846616/

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