Calculation of the IR spectrum of (22S,23S)-24-epicastasterone

Normal vibrational frequencies and absolute IR band intensities for the biologically active steroidal phytohormone (22S,23S)-24-epicastasterone have been calculated within the framework of an original combined approach that uses classical normal coordinate analysis by means of the molecular mechanics method coupled with the quantum-chemical estimation of absolute intensities. Absorption bands in the IR spectrum of this molecule in the region 1500-900 cm⁻¹ were first interpreted based on a comparison of the experimental IR spectrum with the calculated optical-density spectral curve. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 768–775, November–December, 2008.