Crystal structure of an ep-oxy-sterol: 9α,11α-ep-oxy-5α-cholest-7-ene-3β,5,6α-triol 3,6-di-acetate.

Vincenzo Piccialli,Roberto Centore,Angela Tuzi

doi:10.1107/s2056989017013391

Vincenzo Piccialli, Roberto Centore + Show 1 more

Open Access

https://doi.org/10.1107/s2056989017013391

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Abstract

The title compound, C31H48O6, is a polyoxygenated ep-oxy steroid obtained by a multi-step synthesis involving oxidation of 7-de-hydro-cholesterol. It crystallizes in the P212121 space group; however, the absolute structure of the molecule in the crystal could not be determined by resonant scattering. The configuration at the C5 and C6 positions is in both cases of the α-type, as is that of the C atoms of the ep-oxy ring. Mol-ecules in the crystal form chains parallel to the b axis by hydrogen bonding between O-H donors and carbonyl O-atom acceptors. Some atoms of the alkyl chain are disordered over two orientations, with a refined occupancy ratio of 0.511 (10):0.489 (10).

Highlights

The title compound, C31H48O6, is a polyoxygenated epoxy steroid obtained by a multi-step synthesis involving oxidation of 7-dehydrocholesterol
The configuration at the C5 and C6 positions is in both cases of the -type, as is that of the C atoms of the epoxy ring
Polyoxygenated steroids (Fig. 1) are metabolites both of terrestrial and marine origin possessing a number of remarkable biological activities (D’Auria et al, 1993)

Summary

Chemical context

Polyoxygenated steroids (Fig. 1) are metabolites both of terrestrial and marine origin possessing a number of remarkable biological activities (D’Auria et al, 1993). We have synthesized and studied, among others, purine nucleoside analogues (D’Errico et al, 2011, 2012a,b; D’Atri et al, 2012; Oliviero et al, 2008, 2010a,b), cyclic ethers and polyethers (Piccialli et al, 2007, 2009; Piccialli, D’Errico et al., 2013; Piccialli, 2014) and nitrogen-rich fused-ring compounds (Centore et al, 2013) Within this program, and on the basis of the reduced amount of direct structural information available on epoxy steroids, we have synthesized the title compound (1), by diacetylation of 3, in turn obtained from cheap commercially available 7-dehydrocholesterol (2) (see Fig. 2), according to a previously reported procedure (Migliuolo et al., 1991). The superposition is very good, apart for a small difference in the torsion angle for the acetyl group at C3

Structural commentary

Database survey

Synthesis and crystallization

Refinement