# Conformational Analysis of 3-Indoleacetamide: Unveiling Structural Rigidity in the Tryptophan-Derived Bioactive Molecule Family

## TL;DR

This study reveals that 3-indoleacetamide has a rigid structure, unlike other tryptophan-derived molecules, which could explain its unique biological roles.

## Contribution

The discovery of conformational rigidity in 3-indoleacetamide provides new insights into structure-activity relationships in bioactive molecules.

## Key findings

- 3-indoleacetamide shows only one stable conformer with distinct rotational transitions.
- The acetamide group imposes structural rigidity, unlike in related tryptophan derivatives.
- This rigidity may correlate with specific biological functions like plant hormone regulation.

## Abstract

The conformational landscape of 3-indoleacetamide, a key intermediate in plant hormone biosynthesis, has been comprehensively investigated using state-of-the-art laser-ablation chirped-pulse Fourier transform microwave (LA-CP-FTMW) and laser-ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy. Remarkably, 3-indoleacetamide exhibits unprecedented conformational rigidity within the tryptophan-derived molecule family, displaying only a single stable conformer characterized by distinctive a-, b-, and c-type rotational transitions. This singular conformational behavior contrasts dramatically with the structural flexibility observed in closely related tryptophan derivatives such as tryptophan, serotonin, tryptamine, and 3-indoleacetic acid. The unique structural constraint imposed by the acetamide functional group provides unprecedented insights into the molecular determinants governing the distinct biological roles of tryptophan-derived compounds. This work establishes a potential correlation between conformational flexibility and biological function, from neurotransmission to plant hormone regulation, offering new perspectives on structure-activity relationships in bioactive natural products.