(5S)-5-Methyl-2-pyrrolidinone
[CAS# 1558-60-7]

Identification

• Classification: Organic raw materials >> Ketone compound
• Name: (5S)-5-Methyl-2-pyrrolidinone
• Molecular Formula: C₅H₉NO
• Molecular Weight: 99.13
• CAS Registry Number: 1558-60-7
• EC Number: 873-532-1
• SMILES: C[C@H]1CCC(=O)N1

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*
• Boiling point: 240.5±9.0 ºC 760 mmHg (Calc.)^*
• Flash point: 127.5±3.7 ºC (Calc.)^*
• Index of refraction: 1.439 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H302-H315-H319-H335
• Precautionary Statements: P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P319-P321-P330-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

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

Discovory and Applicatios

(5S)-5-Methyl-2-pyrrolidinone is a chiral five-membered lactam belonging to the family of substituted pyrrolidinones. The compound is structurally derived from 2-pyrrolidinone, a simple cyclic amide widely used in industrial chemistry and pharmaceutical synthesis. The presence of a stereogenic center at the 5-position introduces chirality and allows this compound to function as a source of enantiomerically enriched material for asymmetric synthesis. Interest in substituted pyrrolidinones originates from their close relationship to naturally occurring pyrrolidines, which appear broadly in alkaloids and pharmaceutical intermediates.

In synthetic chemistry, (5S)-5-methyl-2-pyrrolidinone serves primarily as an intermediate, where its chiral center can be transferred or transformed in the construction of more complex molecules. The compound’s stereochemistry provides a controlled starting point for reactions that rely on the preservation or induction of chirality. Enantiomerically enriched pyrrolidinones are commonly used to access substituted γ-lactams, chiral amines, and other nitrogen-containing building blocks that appear throughout medicinal chemistry. While (5S)-5-methyl-2-pyrrolidinone itself is not commonly used as a final active ingredient or functional material, it participates in multistep synthetic sequences where the cyclic amide undergoes transformations such as reduction, alkylation, or ring opening.

Methods reported for preparing enantioenriched 5-methylpyrrolidinones generally involve asymmetric transformations of precursors such as 5-methyl-3-pyrrolin-2-ones, chiral auxiliary-controlled reductions, or enzymatic resolutions of racemic intermediates. These approaches mirror the general strategies used to obtain chiral pyrrolidinone derivatives across the literature, although published procedures tend to address broader families of lactams rather than this specific compound in isolation. The lactam framework is chemically robust and tolerates a variety of functional group manipulations, making it a convenient scaffold for conversion to chiral amines. After reduction, for example, enantioenriched 5-methylpyrrolidinones yield substituted pyrrolidines, which are valuable heterocycles in drug discovery.

Pyrrolidinone derivatives—including substituted and chiral forms—have long served as privileged structures in medicinal chemistry. Although (5S)-5-methyl-2-pyrrolidinone is not a well-documented active pharmaceutical ingredient, related compounds appear in inhibitors of carbohydrate-processing enzymes, ligands for neurotransmitter systems, and precursors to antiviral and anticancer scaffolds. The compound’s utility is therefore indirect: it contributes to the accessible pool of stereochemically defined intermediates that enable medicinal chemists to explore structure–activity relationships efficiently.

Beyond pharmaceutical synthesis, substituted pyrrolidinones can participate in polymer chemistry or specialty materials research where lactam units are incorporated into polyamide backbones. In these contexts, they are usually used in racemic or achiral form because stereodefined monomers do not typically provide functional advantages in bulk materials. As a result, the applications of (5S)-5-methyl-2-pyrrolidinone remain concentrated in small-molecule synthetic chemistry rather than large-scale industrial materials.

Overall, (5S)-5-methyl-2-pyrrolidinone is best understood as a chiral building block used to introduce stereochemistry into more complex molecules. Its value lies in its structural simplicity, reliable amide reactivity, and enantiomeric form, all of which allow chemists to construct chiral frameworks with predictable outcomes. While the compound does not have a well-documented discovery narrative or independent technological application, it plays a supporting role in the broader landscape of heterocycle synthesis and medicinal chemistry.

References

2005. Acylation of Amides. Science of Synthesis.
URL: SD-021-00240

2005. Synthesis from Activated Esters. Science of Synthesis.
URL: SD-021-00236