Isopentyl 4-methoxycinnamate
[CAS# 71617-10-2]

Identification

• Classification: Flavors and spices >> Synthetic spice >> Aromatic cinnamic acid, esters and derivatives
• Name: Isopentyl 4-methoxycinnamate
• Synonyms: Isoamyl p-methoxycinnamate; Isopentyl p-methoxycinnamate; 3-Methylbutyl (E)-3-(4-methoxyphenyl)prop-2-enoate
• Molecular Formula: C₁₅H₂₀O₃
• Molecular Weight: 248.32
• CAS Registry Number: 71617-10-2
• EC Number: 275-702-5
• SMILES: CC(C)CCOC(=O)C=CC1=CC=C(C=C1)OC

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*
• Boiling point: 362.8±17.0 ºC 760 mmHg (Calc.)^*
• Flash point: 151.6±15.5 ºC (Calc.)^*
• Index of refraction: 1.524 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H315-H319-H335
• Precautionary Statements: P261-P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413

Discovory and Applicatios

Isopentyl 4-methoxycinnamate, also widely known as amyl methoxycinnamate or isoamyl p-methoxycinnamate, is an ester compound belonging to the cinnamate family. Structurally, it is derived from 4-methoxycinnamic acid, where the carboxyl group is esterified with isopentanol (isoamyl alcohol). The molecule combines an aromatic cinnamate backbone with an aliphatic side chain, giving it both lipophilic and aromatic characteristics.

The compound was developed in the mid-20th century during efforts to discover effective chemical sunscreens. Cinnamate derivatives were of particular interest because they absorb ultraviolet (UV) light in the UV-B region (280–320 nm), which is primarily responsible for sunburn and contributes significantly to skin cancer risk. Researchers found that substitution of cinnamic acid esters with alkyl chains such as isopentyl enhanced solubility in oils and improved the stability of sunscreen formulations.

Isopentyl 4-methoxycinnamate is best known for its application as a UV filter in sunscreen and cosmetic products. Its ability to absorb UV-B radiation allows it to protect the skin from erythema (sunburn) and long-term photodamage. Compared with earlier sunscreen agents, it demonstrates good photostability and compatibility with other cosmetic ingredients, making it suitable for incorporation into lotions, creams, and sprays. In addition to sunscreens, it has been used in daily skincare products such as moisturizers and lip balms to provide protection against incidental sun exposure.

In terms of synthesis, the compound is typically produced by esterification of 4-methoxycinnamic acid with isopentyl alcohol, often in the presence of an acid catalyst. Industrial-scale production emphasizes purification steps to remove unreacted starting materials and byproducts, ensuring compliance with safety and quality standards required for cosmetic applications.

Safety and regulatory considerations have played a major role in its use. Toxicological studies indicate that isopentyl 4-methoxycinnamate has a low acute toxicity profile and does not show significant systemic absorption when applied to the skin under normal conditions. However, like many UV filters, it has been subject to regulatory reviews to evaluate potential endocrine-disrupting activity and environmental impact. While considered safe at regulated concentrations in many jurisdictions, its use in sunscreens has been restricted or banned in certain regions due to environmental concerns, particularly with regard to coral reef ecosystems where chemical UV filters can accumulate and potentially disrupt marine life.

Chemically, isopentyl 4-methoxycinnamate is relatively stable under neutral conditions but can undergo photodegradation upon prolonged exposure to UV light. To improve its stability in formulations, it is often combined with other UV filters and stabilizers that broaden the absorption spectrum and prevent breakdown. This synergistic approach enhances both efficacy and durability in real-world sunscreen applications.

The compound has also been investigated for potential roles beyond sunscreen formulations. Its cinnamate backbone suggests possible antioxidant and photoprotective activity, though these properties are secondary to its primary function as a UV filter. Additionally, derivatives of 4-methoxycinnamic acid, including isopentyl 4-methoxycinnamate, have been studied as intermediates in organic synthesis, particularly in the design of aromatic compounds with biological activity.

Overall, isopentyl 4-methoxycinnamate represents a successful example of how organic chemistry has contributed to public health by reducing risks associated with sun exposure. Its development and application highlight the intersection of chemical design, safety evaluation, and environmental responsibility, ensuring that while it protects human health, its broader ecological effects are carefully monitored.

References

2011. Simultaneous determination of some ultraviolet-absorbing chemicals in sunscreen cosmetics using a high-performance liquid chromatography method. International Journal of Cosmetic Science.
DOI: 10.1111/j.1468-2494.2011.00643.x

2011. Photo-allergic contact dermatitis caused by isoamyl p-methoxycinnamate in an �organic� sunscreen. Contact Dermatitis.
DOI: 10.1111/j.1600-0536.2010.01839.x

2019. Generating the Blood Exposome Database Using a Comprehensive Text Mining and Database Fusion Approach. Environmental Health Perspectives.
DOI: 10.1289/ehp4713