Steroid Hormone Androsterone Observed in the Gas Phase by Rotational Spectroscopy.

We report the investigation of the steroid hormone androsterone in the gas phase. Androsterone is a male sex steroid hormone, being the first steroid hormone from this category isolated and discovered 90 years ago. Despite the chemical compositions of steroids being well-known since long ago, studying their structures in the gas phase is still a challenging task, and to date, just a handful of detailed experimental structures for steroids have been reported. The rotational spectrum of androsterone was recorded in the 2-8 GHz frequency region with a broadband chirped-pulse Fourier transform microwave spectrometer coupled with supersonic expansion. From the weak rotational spectrum, one conformer has been detected in the isolated and cold conditions of the molecular jet. The combination of the experimental results with quantum chemical calculations allowed us to unambiguously identify the conformation of androsterone in the gas phase.