Acta Crystallographica Section B

Structural Science

Volume 57, Part 5 (October 2001)


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Acta Cryst. (2001). B57, 714-721    [doi:10.1107/S0108768101013234]

Studies of molecular structure parameters of 20-piperidin-2-yl-5[alpha]-pregnan-3[beta],20-diol and its N-methyl derivative: two inhibitors of [Delta]24(25) sterol methyl transferase and [Delta]24(24') sterol methyl reductase of Trypanosoma cruzi

R. Atencio, G. Visbal, S. Pekerar, J. Papale and J. A. Urbina

Abstract: Molecular structural parameters of two potential drugs against Trypanosoma cruzi epimastigotes, 20-piperidin-2-yl-5[alpha]-pregnan-3[beta],20-diol (1) and 20-N-methylpiperidin-2-yl-5[alpha]-pregnan-3[beta], 20-diol (2) were studied using a combination of a stereoselective synthetic route, spectroscopic characterization and single-crystal X-ray analysis. Both compounds were synthesized with an R configuration at C20. This chirality is a consequence of the stereoselectivity observed during the formation of the intermediate 20-pyridin-2-yl-5[alpha]-pregnan-3[beta],20R-diol (4). NMR data indicated that the six-membered aza ring of (2) is conformationally more restrained, in CDCl3 solution, than (1). X-ray studies showed that maximum deviations among structural molecular parameters of (1) and (2) correspond to torsion angles along the C20-C22 bonds, leading to a different relative orientation of the N atom; a critical structural parameter for the binding properties of aza-sterols to [Delta]24(25) sterol methyl transferase. Cremer-Pople parameters of the five-membered rings of (1) and (2) lie in the observed range for a family of tetracyclic fused ring systems retrieved from the CSD. The [bold varphi]2 parameter of (1) lies just on the mean of the family, while [bold varphi]2 of (2) deviates significantly towards the lower limit.

Online 29 September 2001

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