Acta Crystallographica Section C

Crystal Structure Communications

Volume 65, Part 4 (April 2009)

organic compounds

 

Absolute structures and conformations of the spongian diterpenes spongia-13(16),14-dien-3-one, epispongiadiol and spongiadiol

K. W. L. Yong, M. J. Garson and P. V. Bernhardt

Abstract: The absolute configurations of spongia-13(16),14-dien-3-one [systematic name: (3bR,5aR,9aR,9bR)-3b,6,6,9a-tetramethyl-4,5,5a,6,8,9,9a,9b,10,11-decahydrophenanthro[1,2-c]furan-7(3bH)-one], C₂₀H₂₈O₂, (I), epispongiadiol [systematic name: (3bR,5aR,6S,7R,9aR,9bR)-7-hydroxy-6-hydroxymethyl-3b,6,9a-trimethyl-3b,5,5a,6,7,9,9a,9b,10,11-decahydrophenanthro[1,2-c]furan-8(4H)-one], C₂₀H₂₈O₄, (II), and spongiadiol [systematic name: (3bR,5aR,6S,7S,9aR,9bR)-7-hydroxy-6-hydroxymethyl-3b,6,9a-trimethyl-3b,5,5a,6,7,9,9a,9b,10,11-decahydrophenanthro[1,2-c]furan-8(4H)-one], C₂₀H₂₈O₄, (III), were assigned by analysis of anomalous dispersion data collected at 130 K with Cu K radiation. Compounds (II) and (III) are epimers. The equatorial 3-hydroxyl group on the cyclohexanone ring (A) of (II) is syn with respect to the 4-hydroxymethyl group, leading to a chair conformation. In contrast, isomer (III), where the 3-hydroxyl group is anti to the 4-hydroxymethyl group, is conformationally disordered between a major chair conformer where the OH group is axial and a minor boat conformer where it is equatorial. In compound (I), a carbonyl group is present at position 3 and ring A adopts a distorted-boat conformation.

Formula: C₂₀H₂₈O₂, C₂₀H₂₈O₄ and C₂₀H₂₈O₄

	Structure factor file (CIF format) (247.9 kbytes) [ doi:10.1107/S0108270109008816/sq3189Isup2.hkl ] Contains datablock I
	Structure factor file (CIF format) (126.2 kbytes) [ doi:10.1107/S0108270109008816/sq3189IIsup3.hkl ] Contains datablock II
	Structure factor file (CIF format) (129.1 kbytes) [ doi:10.1107/S0108270109008816/sq3189IIIsup4.hkl ] Contains datablock III

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