Synthesis of diosgenin p-nitrobenzoate by Steglich method, its crystal structure and quantum chemical studies

In the present study, a novel one pot synthetic route for the synthesis of diosgenin p-nitrobenzoate (2) is described from cheap, commercially available naturally occurring sapogenin–diosgenin. The molecular geometry, IR frequencies, Gauge-including atomic orbital (GIAO), 1H and 13C NMR chemical shifts of compound 2 has been calculated in the ground state by using the Hartree–Fock (HF) and density functional method (DFT/B3LYP) using 6-31G(d,p) basis set. The structure of diosgenin p-nitrobenzoate (2) has been confirmed by single crystal X-ray diffraction. The compound crystallizes in monoclinic form having space group P21 with cell parameters a = 7.719(2) Å, b = 8.425(2) Å and c = 22.578(6) Å, α = 90.00, β = 98.46 and γ = 90.00. The oxygen atoms O5 and O4 of the nitro and carbonyl ester, respectively display weak intermolecular N1O5⋯H7′ and C1′O4⋯H4′ interactions having dimensions of 2.61 and 2.59 Å, respectively to form intricate 1D network. The study of the electronic properties such as HOMO and LUMO energy were performed using time dependent DFT (TD-DFT) calculations. The calculated HOMO and LUMO energy values indicate that charge transfer takes place within the molecule. The compound was screened for cytotoxicity and anti-adipogenic activity.

► One pot Steglich esterification of diosgenin, without opening of spiro ring in high yield.
► Stereochemistry assigned to the title compound using X-ray crystallography.
► Theoretical calculations made using DFT/B3LYP/6-31G(d,p) method.
► Chemical reactivity explained with the aid of molecular elestroscostatic potential surface.
► The title compound was screened for cytotoxicity and anti-adipogenic activity.