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Cholesteryl pentyl carbonate (C33H56O3) is monoclinic, space group P21, with a = 12.484(3), b = 9.043(3), c = 14.053(3)Å, β = 94.12(2)° and z = 2. The intensity data were measured for the 2969 reflections within sin θ/λ = 0.52 Å-1, using an automatic four--circle diffractometer and graphite monochromated Mo-Kα radiation. The atomic coordinates from cholesteryl octanoate were used in an initial trial structure and the structure was refined by full-matrix least squares methods. The final R-factor was 0.12 for 1164 observed reflections. The pentyl group has shortened bond lengths due to the high thermal vibrations in this region. Adjacent molecules are related by 21 screw axis so that they are arranged in an antiparallel array, corresponding to the Monolayer Type Ⅱ packing mode. There are close packings of cholesteryl groups within the monolayers. This packing type is similar to those of cholesteryl hexanoate, octanoate, hexyl carbonate and oleate.
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