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1 Polish Journal of Chemistry

1 1999

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Crystal and molecular structure of 3B-acetoxy-21-(2-hydroxy-2methylopropoxy)-cholest-5-en-25-ol, the first "double side chain" choresterol analogue investigated by X-ray diffraction

Gałdecka E., Gałdecki Z., Górkiewicz Z., Kurek-Tyrlik A., Makaev F., Wicha J., Calverley M.

Polish Journal of Chemistry

1999

vol. 73 nr 3

541-555

The title steroid crystallizes in the monoclinic P21 space group with unit cell dimensions: a=11.745(2) A, b=10.564(2) A, c=12.979(3) A, b = 95.73(3)0. Its crystal and molecular structure was determined by X-ray diffraction methods. The A ring has a symmetrical chair conformation. The B ring has a half-chair conformation, with asymmetry parameter D5,62=0.60. The C ring has an intermediate sofa-half-chair conformation with asymmetry parameters: DC9s=2.30, DC11s=5.80, DC9,112=4.80, and DC8,92=5.60. The D ring adopts an envelope conformation with asymmetry parameter DC13s=10.70. The cholesterol side chain adopts a fully extended conformation with torsion angles -170.6(6)0, 167.9(6)0 , -171.9(6)0 , and 175.6(7)0 , i.e. it belongs to the most populated conformer A, and with the terminal C26 and C27 methyl groups in gauche, trans conformations.