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organic compounds
(–)-(5S,8S,9R,10S,13R,14R)-15,16-Dideoxy-16,17-epoxy-16-oxospongian-15-yl acetate
aSchool of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, England, and bDepartamento de Química Orgánica/Instituto de Ciencia Molecular (ICMOL), Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia, Spain
*Correspondence e-mail: a.j.blake@nottingham.ac.uk, miguel.a.gonzalez@uv.es
The title compound (aplyroseol-14), C22H34O4, exhibits a lactone-based structure that is novel for spongian-type The structure, which features a six-membered lactone ring, was proposed by Arnó, González & Zaragozá [J. Org. Chem. (2003), 68, 1242–1251] on the basis of spectroscopic data and chemical correlations. This assignment has been confirmed, and it is shown that the molecule contains a trans–anti–trans 6/6/6 tricyclic hydrocarbon system and that the acetoxymethyl group lies in an equatorial position. Pairs of near-linear C—H⋯O interactions link molecules into extended chains.
Comment
are bioactive natural products isolated exclusively from sponges and shell-less molluscs (nudibranchs), which are believed to be capable of sequestering the spongian-derived metabolites from the sponges on which they feed. Most of these compounds play a key role as eco-physiological mediators and are of interest as potential therapeutic agents (Arnó, Betancur-GalvisThe carbon skeleton (I), named `spongian' in accordance with IUPAC recommendations (Kazlauskas et al., 1979
), was chosen as the fundamental parent structure for this family of natural compounds, with the numbering depicted. Thus, spongians typically exhibit the hydrocarbon ring system (I)
, consisting of a steroid-like ABCD ring system containing an oxygenated group, such as a tetrahydrofuran ring, and with varying oxidation patterns on rings A–D.
The title compound, (1b), was isolated from the sponge Aplysilla rosea Barrois by Taylor & Toth (1997
), and the structure (1a)
, in which ring D is usually a five-membered lactone typical of other members of the spongian family (Cimino et al., 1974
; Karuso & Taylor, 1986
; Miyamoto et al., 1996
), was assigned from one- and two-dimensional 1H NMR data, high-resolution and IR spectroscopy. Following our studies directed towards the synthesis of C-17-functionalized spongians (Arnó et al., 2001
), we selected (1a)
as a potential target compound and we readily synthesized
![Arnó, M., González, M. A. & Zaragozá, R. J. (2003). J. Org. Chem. 68, 1242-1251. [Arnó, M., González, M. A. & Zaragozá, R. J. (2003). J. Org. Chem. 68, 1242-1251.]](../../../../../../logos/arrows/c_arr.gif)
![[link]](../../../../../../logos/arrows/c_arr.gif)
![Karuso, P. & Taylor, W. C. (1986). Aust. J. Chem. 39, 1629-1641. [Karuso, P. & Taylor, W. C. (1986). Aust. J. Chem. 39, 1629-1641.]](../../../../../../logos/arrows/c_arr.gif)
![Miyamoto, T., Sakamoto, K., Arao, K., Komori, T., Higuchi, R. & Sasaki, T. (1996). Tetrahedron, 52, 8187-8198. [Miyamoto, T., Sakamoto, K., Arao, K., Komori, T., Higuchi, R. & Sasaki, T. (1996). Tetrahedron, 52, 8187-8198.]](../../../../../../logos/arrows/c_arr.gif)
![[link]](../../../../../../logos/arrows/c_arr.gif)
![[link]](../../../../../../logos/arrows/c_arr.gif)
![[link]](../../../../../../logos/arrows/c_arr.gif)
![[link]](../../../../../../logos/arrows/c_arr.gif)
![[link]](../../../../../../logos/arrows/c_arr.gif)
![[link]](../../../../../../logos/arrows/c_arr.gif)
![[link]](../../../../../../logos/arrows/c_arr.gif)
A perspective view of the molecule is shown in Fig. 1. Both the chemical connectivity and the relative stereochemistry are in full agreement with those proposed by Arnó, González & Zaragozá (2003
) for aplyroseol-14 (1b)
. The stereochemistry at atoms C5 (S), C9 (R) and C10 (S) is invariant during the synthesis, but three new asymmetric centres were introduced at C8 (S), C13 (R) and C14 (R). The molecule contains a trans–anti–trans 6/6/6 tricyclic hydrocarbon system to which a six-membered lactone ring is attached at atoms C8 and C13. All six-membered rings adopt chair conformations with axially disposed methyl or lactone substituents. However, the lactone ring (C8/C14/C13/C16/O17/C17) is distorted towards a half-chair conformation; while atom C8 lies 0.734 (3) Å below the least-squares mean plane through atoms C14, C13, O17 and C17, atom C16 lies only 0.329 (3) Å above it. The acetoxymethyl group at atom C14 lies in an equatorial position. Bond lengths and angles are typical for such sterically non-strained molecules.
Molecules are linked by almost linear pairwise C—H⋯O interactions (Table 1 and Fig. 2
). One of these interactions occurs between carbonyl atom O21 of the acetoxy group and atom H15 of the methylene group adjacent to the acetoxy group in a neighbouring molecule; the other involves methine atom H14 and lactone atom O17 in the same neighbouring molecule. The interactions link the molecules into chains running along the b axis. The C—H⋯O interactions contrast with the situation in analogous compounds containing hydroxy groups (Schmitz et al., 1985
; Karuso et al., 1986
; Miyamoto et al., 1996
), where the presence of the hydroxy groups leads to O—H⋯O=C hydrogen bonds being the primary intermolecular contacts.
![]() | Figure 1 A view of (1b), showing the atom-numbering scheme and displacement ellipsoids at the 50% probability level. |
![]() | Figure 2 A view of the chains of molecules linked along the b axis by pairwise near-linear C—H⋯O interactions. C atoms are shown as large open circles, O atoms as dotted circles and H atoms as small open circles. [Symmetry codes: (i) x, y + 1, z; (ii) x, y − 1, z.] |
Experimental
Compound (1b) was synthesized from the chiral synthon (+)-podocarp-8(14)-en-13-one, readily available from commercial (−)-abietic acid (Abad et al., 1985; see scheme
below). The absolute stereochemistry at atoms C5, C9 and C10 was therefore fixed. During the synthesis, the key intermediate methyl 8β,14β-dioxopodocarpan-13β-oate was prepared, in which three new stereocentres, viz. C8, C13 and C14, were introduced. This intermediate was transformed into (−)-16-oxospongian-17-al, confirming the absolute stereochemistry of all asymmetric centres. Finally, the latter was converted into (1b)
by standard reduction followed by acetylation. This two-step process involved a translactonization reaction that occurred during the reduction step. Crystals were grown from a solution of (1b)
in dichloromethane/hexane (1:4).
Crystal data
|
Data collection
|
Refinement
|
|
The b) was assigned as for (+)-podocarp-8(14)-en-13-one (Abad et al., 1985
), based on the of (−)-abietic acid as determined by optical rotatory dispersion measurements (e.g. Bose & Struck, 1959
). All H atoms were included at geometrically calculated positions and constrained to ride on their parent C atoms at distances of 0.98, 0.99 or 1.00 Å for methyl, methylene or methine groups, respectively, and with Uiso(H) values of 1.5Ueq(C) for methyl H atoms and 1.2Ueq(C) for others. As there are no significant effects, Friedel opposites were merged prior to the final cycles of refinement.
Data collection: SMART (Bruker, 2001); cell SAINT (Bruker, 2001
); data reduction: SAINT and SHELXTL (Bruker, 2001
); program(s) used to solve structure: SIR2002 (Burla et al., 2003
); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997
); molecular graphics: PLATON (Spek, 2003
) and SHELXTL; software used to prepare material for publication: enCIFer (Allen et al., 2004
) and PLATON.
Supporting information
10.1107/S0108270106006366/ln3004sup1.cif
contains datablocks global, 1b. DOI:Structure factors: contains datablock 1b. DOI: 10.1107/S0108270106006366/ln30041bsup2.hkl
Compound (1b) was synthesized from the chiral synthon (+)-podocarp-8(14)-en-13-one, readily available from commercial (-)-abietic acid (Abad et al., 1985; see Scheme 2). The absolute stereochemistry at atoms C5, C9 and C10 was therefore fixed. During the synthesis, the key intermediate methyl 8β,14β-dioxopodocarpan-13β-oate was prepared, in which three new stereocenters, C8, C13 and C14, were introduced. This intermediate was transformed into (-)-spongian-16-oxo-17-al confirming the absolute stereochemistry of all asymmetric centers. Finally, the latter was converted into aplyroseol-14, (1b), by standard reduction followed by acetylation. This two-step process involved a translactonization reaction that occurred during the reduction step. Crystals were grown from a solution of (1b) in dichloromethane/hexane (1/4).
The
of (1b) was assigned as assumed for (+)-podocarp-8(14)-en-13-one (Abad et al., 1985). All H atoms were included at geometrically calculated positions and constrained to ride on their parent C atom at a distance of 0.98, 0.99 or 1.00 Å for methyl, methylene or methine groups, respectively, and with Uiso(H) values of 1.5Ueq(C) for methyl H atoms and 1.2Ueq(C) for others. As there are no significant effects, Friedel opposites were merged prior to the final cycles of refinement.Data collection: SMART (Bruker, 2001); cell
SAINT (Bruker, 2001); data reduction: SAINT and SHELXTL (Bruker, 2001); program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: enCIFer (Allen et al., 2004) and PLATON.C22H34O4 | F(000) = 792 |
Mr = 362.49 | Dx = 1.245 Mg m−3 |
Monoclinic, C2 | Melting point = 419–421 K |
Hall symbol: C 2y | Mo Kα radiation, λ = 0.71073 Å |
a = 13.377 (2) Å | Cell parameters from 3476 reflections |
b = 6.0824 (8) Å | θ = 2.6–27.5° |
c = 23.834 (3) Å | µ = 0.08 mm−1 |
β = 94.235 (2)° | T = 150 K |
V = 1933.9 (5) Å3 | Tablet, colourless |
Z = 4 | 1.07 × 0.50 × 0.13 mm |
Bruker SMART APEX CCD area-detector diffractometer | 2200 reflections with I > 2σ(I) |
Radiation source: sealed tube | Rint = 0.133 |
Graphite monochromator | θmax = 27.5°, θmin = 2.6° |
ω scans | h = −17→15 |
5352 measured reflections | k = −7→7 |
2382 independent reflections | l = −30→22 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.049 | H-atom parameters constrained |
wR(F2) = 0.133 | w = 1/[σ2(Fo2) + (0.106P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.92 | (Δ/σ)max = 0.001 |
2382 reflections | Δρmax = 0.40 e Å−3 |
239 parameters | Δρmin = −0.27 e Å−3 |
1 restraint |
C22H34O4 | V = 1933.9 (5) Å3 |
Mr = 362.49 | Z = 4 |
Monoclinic, C2 | Mo Kα radiation |
a = 13.377 (2) Å | µ = 0.08 mm−1 |
b = 6.0824 (8) Å | T = 150 K |
c = 23.834 (3) Å | 1.07 × 0.50 × 0.13 mm |
β = 94.235 (2)° |
Bruker SMART APEX CCD area-detector diffractometer | 2200 reflections with I > 2σ(I) |
5352 measured reflections | Rint = 0.133 |
2382 independent reflections |
R[F2 > 2σ(F2)] = 0.049 | 1 restraint |
wR(F2) = 0.133 | H-atom parameters constrained |
S = 0.92 | Δρmax = 0.40 e Å−3 |
2382 reflections | Δρmin = −0.27 e Å−3 |
239 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.17249 (16) | 0.5239 (4) | 0.64125 (8) | 0.0223 (4) | |
H1A | 0.1075 | 0.4550 | 0.6481 | 0.027* | |
H1B | 0.1710 | 0.6774 | 0.6550 | 0.027* | |
C2 | 0.18436 (16) | 0.5260 (5) | 0.57783 (8) | 0.0261 (5) | |
H2A | 0.1790 | 0.3739 | 0.5631 | 0.031* | |
H2B | 0.1295 | 0.6137 | 0.5587 | 0.031* | |
C3 | 0.28490 (18) | 0.6232 (5) | 0.56464 (9) | 0.0287 (5) | |
H3A | 0.2857 | 0.7812 | 0.5747 | 0.034* | |
H3B | 0.2913 | 0.6124 | 0.5236 | 0.034* | |
C4 | 0.37618 (16) | 0.5113 (4) | 0.59559 (8) | 0.0233 (5) | |
C5 | 0.35872 (16) | 0.4998 (4) | 0.65979 (8) | 0.0198 (4) | |
H5 | 0.3554 | 0.6569 | 0.6719 | 0.024* | |
C6 | 0.44649 (16) | 0.4030 (4) | 0.69668 (8) | 0.0219 (4) | |
H6A | 0.4495 | 0.2422 | 0.6905 | 0.026* | |
H6B | 0.5101 | 0.4678 | 0.6857 | 0.026* | |
C7 | 0.43527 (15) | 0.4490 (4) | 0.75898 (8) | 0.0213 (4) | |
H7A | 0.4386 | 0.6098 | 0.7653 | 0.026* | |
H7B | 0.4923 | 0.3813 | 0.7815 | 0.026* | |
C8 | 0.33666 (16) | 0.3610 (3) | 0.78006 (8) | 0.0186 (4) | |
C9 | 0.24753 (15) | 0.4441 (3) | 0.73928 (8) | 0.0182 (4) | |
H9 | 0.2502 | 0.6079 | 0.7427 | 0.022* | |
C10 | 0.25741 (16) | 0.3985 (3) | 0.67533 (8) | 0.0177 (4) | |
C11 | 0.14387 (16) | 0.3811 (4) | 0.75895 (9) | 0.0226 (4) | |
H11A | 0.0912 | 0.4600 | 0.7355 | 0.027* | |
H11B | 0.1331 | 0.2215 | 0.7531 | 0.027* | |
C12 | 0.13324 (16) | 0.4360 (4) | 0.82095 (8) | 0.0233 (4) | |
H12A | 0.0707 | 0.3698 | 0.8330 | 0.028* | |
H12B | 0.1286 | 0.5974 | 0.8255 | 0.028* | |
C13 | 0.22299 (18) | 0.3487 (4) | 0.85824 (9) | 0.0219 (4) | |
H13 | 0.2150 | 0.3927 | 0.8981 | 0.026* | |
C14 | 0.31962 (16) | 0.4501 (3) | 0.83942 (8) | 0.0191 (4) | |
H14 | 0.3080 | 0.6120 | 0.8356 | 0.023* | |
O15 | 0.38191 (13) | 0.5208 (3) | 0.93589 (6) | 0.0271 (4) | |
C15 | 0.40754 (18) | 0.4176 (4) | 0.88379 (8) | 0.0232 (5) | |
H15 | 0.4202 | 0.2588 | 0.8900 | 0.028* | |
H15B | 0.4690 | 0.4853 | 0.8708 | 0.028* | |
O16 | 0.16935 (14) | −0.0141 (3) | 0.88247 (8) | 0.0368 (4) | |
C16 | 0.21947 (18) | 0.0995 (4) | 0.85418 (9) | 0.0253 (5) | |
O17 | 0.26571 (13) | 0.0020 (3) | 0.81182 (7) | 0.0271 (4) | |
C17 | 0.34732 (17) | 0.1109 (4) | 0.78647 (9) | 0.0226 (4) | |
H17A | 0.3538 | 0.0464 | 0.7488 | 0.027* | |
H17B | 0.4103 | 0.0794 | 0.8096 | 0.027* | |
C18 | 0.46733 (19) | 0.6582 (5) | 0.58765 (10) | 0.0331 (6) | |
H18A | 0.4714 | 0.6888 | 0.5475 | 0.050* | |
H18B | 0.5285 | 0.5829 | 0.6024 | 0.050* | |
H18C | 0.4603 | 0.7968 | 0.6080 | 0.050* | |
C19 | 0.3960 (2) | 0.2883 (5) | 0.56855 (9) | 0.0306 (5) | |
H19A | 0.4155 | 0.3111 | 0.5301 | 0.046* | |
H19B | 0.3350 | 0.1986 | 0.5675 | 0.046* | |
H19C | 0.4502 | 0.2126 | 0.5907 | 0.046* | |
C20 | 0.24679 (17) | 0.1503 (4) | 0.66120 (9) | 0.0233 (4) | |
H20A | 0.2072 | 0.0784 | 0.6889 | 0.035* | |
H20B | 0.3134 | 0.0829 | 0.6622 | 0.035* | |
H20C | 0.2130 | 0.1327 | 0.6236 | 0.035* | |
O21 | 0.43121 (13) | 0.8479 (3) | 0.90373 (7) | 0.0309 (4) | |
C21 | 0.39490 (18) | 0.7387 (4) | 0.93946 (8) | 0.0260 (5) | |
C22 | 0.3563 (2) | 0.8273 (5) | 0.99275 (10) | 0.0385 (6) | |
H22A | 0.3875 | 0.9701 | 1.0017 | 0.058* | |
H22B | 0.3729 | 0.7244 | 1.0237 | 0.058* | |
H22C | 0.2834 | 0.8450 | 0.9876 | 0.058* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0168 (9) | 0.0248 (10) | 0.0245 (9) | 0.0007 (8) | −0.0048 (7) | −0.0005 (8) |
C2 | 0.0203 (10) | 0.0348 (12) | 0.0219 (9) | −0.0002 (10) | −0.0068 (7) | 0.0014 (9) |
C3 | 0.0316 (12) | 0.0304 (12) | 0.0233 (10) | −0.0042 (10) | −0.0026 (8) | 0.0033 (9) |
C4 | 0.0184 (10) | 0.0316 (12) | 0.0193 (9) | −0.0048 (9) | −0.0021 (7) | −0.0023 (9) |
C5 | 0.0190 (10) | 0.0206 (10) | 0.0193 (8) | −0.0024 (8) | −0.0026 (7) | −0.0014 (8) |
C6 | 0.0155 (10) | 0.0279 (11) | 0.0219 (9) | −0.0015 (8) | −0.0014 (7) | −0.0018 (8) |
C7 | 0.0146 (9) | 0.0274 (11) | 0.0211 (9) | −0.0031 (9) | −0.0045 (7) | −0.0003 (8) |
C8 | 0.0186 (10) | 0.0177 (10) | 0.0189 (9) | −0.0012 (8) | −0.0020 (7) | −0.0005 (7) |
C9 | 0.0182 (9) | 0.0165 (9) | 0.0193 (8) | 0.0013 (8) | −0.0035 (7) | −0.0004 (7) |
C10 | 0.0129 (9) | 0.0201 (10) | 0.0194 (8) | −0.0005 (7) | −0.0031 (7) | −0.0026 (7) |
C11 | 0.0183 (10) | 0.0263 (11) | 0.0225 (9) | 0.0007 (8) | −0.0019 (7) | 0.0004 (8) |
C12 | 0.0209 (10) | 0.0244 (11) | 0.0245 (10) | 0.0026 (9) | 0.0015 (8) | 0.0003 (9) |
C13 | 0.0245 (11) | 0.0197 (10) | 0.0214 (9) | −0.0014 (9) | 0.0006 (8) | 0.0013 (8) |
C14 | 0.0204 (10) | 0.0170 (9) | 0.0194 (8) | −0.0004 (8) | −0.0026 (7) | 0.0005 (7) |
O15 | 0.0348 (9) | 0.0272 (8) | 0.0189 (7) | −0.0042 (8) | −0.0018 (6) | 0.0008 (6) |
C15 | 0.0265 (11) | 0.0220 (10) | 0.0203 (9) | 0.0009 (8) | −0.0046 (8) | 0.0004 (8) |
O16 | 0.0387 (10) | 0.0287 (9) | 0.0434 (10) | −0.0067 (8) | 0.0052 (8) | 0.0100 (8) |
C16 | 0.0266 (12) | 0.0219 (10) | 0.0266 (10) | −0.0003 (9) | −0.0034 (8) | 0.0045 (9) |
O17 | 0.0317 (9) | 0.0171 (7) | 0.0323 (8) | −0.0017 (7) | 0.0002 (6) | 0.0022 (6) |
C17 | 0.0214 (10) | 0.0203 (10) | 0.0256 (9) | 0.0025 (8) | −0.0019 (8) | 0.0013 (8) |
C18 | 0.0280 (12) | 0.0452 (15) | 0.0261 (10) | −0.0139 (11) | 0.0005 (9) | 0.0028 (10) |
C19 | 0.0303 (12) | 0.0368 (12) | 0.0248 (10) | 0.0004 (10) | 0.0020 (9) | −0.0077 (10) |
C20 | 0.0218 (10) | 0.0207 (10) | 0.0272 (10) | −0.0031 (8) | −0.0001 (8) | −0.0050 (8) |
O21 | 0.0365 (10) | 0.0263 (8) | 0.0299 (8) | −0.0033 (8) | 0.0012 (7) | −0.0004 (7) |
C21 | 0.0301 (12) | 0.0281 (12) | 0.0190 (9) | −0.0004 (10) | −0.0045 (8) | −0.0029 (9) |
C22 | 0.0455 (15) | 0.0419 (15) | 0.0283 (11) | −0.0005 (13) | 0.0041 (10) | −0.0100 (11) |
C1—C2 | 1.532 (3) | C12—C13 | 1.535 (3) |
C1—C10 | 1.548 (3) | C12—H12A | 0.9900 |
C1—H1A | 0.9900 | C12—H12B | 0.9900 |
C1—H1B | 0.9900 | C13—C16 | 1.519 (3) |
C2—C3 | 1.523 (3) | C13—C14 | 1.529 (3) |
C2—H2A | 0.9900 | C13—H13 | 1.0000 |
C2—H2B | 0.9900 | C14—C15 | 1.535 (3) |
C3—C4 | 1.538 (3) | C14—H14 | 1.0000 |
C3—H3A | 0.9900 | O15—C21 | 1.339 (3) |
C3—H3B | 0.9900 | O15—C15 | 1.455 (3) |
C4—C19 | 1.533 (4) | C15—H15 | 0.9900 |
C4—C18 | 1.535 (3) | C15—H15B | 0.9900 |
C4—C5 | 1.566 (3) | O16—C16 | 1.204 (3) |
C5—C6 | 1.531 (3) | C16—O17 | 1.359 (3) |
C5—C10 | 1.558 (3) | O17—C17 | 1.447 (3) |
C5—H5 | 1.0000 | C17—H17A | 0.9900 |
C6—C7 | 1.529 (3) | C17—H17B | 0.9900 |
C6—H6A | 0.9900 | C18—H18A | 0.9800 |
C6—H6B | 0.9900 | C18—H18B | 0.9800 |
C7—C8 | 1.542 (3) | C18—H18C | 0.9800 |
C7—H7A | 0.9900 | C19—H19A | 0.9800 |
C7—H7B | 0.9900 | C19—H19B | 0.9800 |
C8—C17 | 1.534 (3) | C19—H19C | 0.9800 |
C8—C14 | 1.548 (3) | C20—H20A | 0.9800 |
C8—C9 | 1.566 (3) | C20—H20B | 0.9800 |
C9—C11 | 1.545 (3) | C20—H20C | 0.9800 |
C9—C10 | 1.564 (3) | O21—C21 | 1.210 (3) |
C9—H9 | 1.0000 | C21—C22 | 1.505 (3) |
C10—C20 | 1.551 (3) | C22—H22A | 0.9800 |
C11—C12 | 1.532 (3) | C22—H22B | 0.9800 |
C11—H11A | 0.9900 | C22—H22C | 0.9800 |
C11—H11B | 0.9900 | ||
C2—C1—C10 | 113.37 (18) | C9—C11—H11B | 109.0 |
C2—C1—H1A | 108.9 | H11A—C11—H11B | 107.8 |
C10—C1—H1A | 108.9 | C11—C12—C13 | 111.03 (17) |
C2—C1—H1B | 108.9 | C11—C12—H12A | 109.4 |
C10—C1—H1B | 108.9 | C13—C12—H12A | 109.4 |
H1A—C1—H1B | 107.7 | C11—C12—H12B | 109.4 |
C3—C2—C1 | 111.37 (17) | C13—C12—H12B | 109.4 |
C3—C2—H2A | 109.4 | H12A—C12—H12B | 108.0 |
C1—C2—H2A | 109.4 | C16—C13—C14 | 114.0 (2) |
C3—C2—H2B | 109.4 | C16—C13—C12 | 106.8 (2) |
C1—C2—H2B | 109.4 | C14—C13—C12 | 109.43 (17) |
H2A—C2—H2B | 108.0 | C16—C13—H13 | 108.8 |
C2—C3—C4 | 114.3 (2) | C14—C13—H13 | 108.8 |
C2—C3—H3A | 108.7 | C12—C13—H13 | 108.8 |
C4—C3—H3A | 108.7 | C13—C14—C15 | 111.54 (17) |
C2—C3—H3B | 108.7 | C13—C14—C8 | 108.16 (16) |
C4—C3—H3B | 108.7 | C15—C14—C8 | 115.32 (18) |
H3A—C3—H3B | 107.6 | C13—C14—H14 | 107.1 |
C19—C4—C18 | 107.43 (19) | C15—C14—H14 | 107.1 |
C19—C4—C3 | 110.23 (18) | C8—C14—H14 | 107.1 |
C18—C4—C3 | 107.0 (2) | C21—O15—C15 | 116.34 (18) |
C19—C4—C5 | 114.4 (2) | O15—C15—C14 | 108.41 (18) |
C18—C4—C5 | 108.89 (17) | O15—C15—H15 | 110.0 |
C3—C4—C5 | 108.55 (17) | C14—C15—H15 | 110.0 |
C6—C5—C10 | 110.79 (17) | O15—C15—H15B | 110.0 |
C6—C5—C4 | 114.51 (17) | C14—C15—H15B | 110.0 |
C10—C5—C4 | 116.42 (16) | H15—C15—H15B | 108.4 |
C6—C5—H5 | 104.5 | O16—C16—O17 | 117.9 (2) |
C10—C5—H5 | 104.5 | O16—C16—C13 | 123.6 (2) |
C4—C5—H5 | 104.5 | O17—C16—C13 | 118.0 (2) |
C7—C6—C5 | 111.16 (17) | C16—O17—C17 | 120.63 (17) |
C7—C6—H6A | 109.4 | O17—C17—C8 | 115.34 (19) |
C5—C6—H6A | 109.4 | O17—C17—H17A | 108.4 |
C7—C6—H6B | 109.4 | C8—C17—H17A | 108.4 |
C5—C6—H6B | 109.4 | O17—C17—H17B | 108.4 |
H6A—C6—H6B | 108.0 | C8—C17—H17B | 108.4 |
C6—C7—C8 | 113.61 (16) | H17A—C17—H17B | 107.5 |
C6—C7—H7A | 108.8 | C4—C18—H18A | 109.5 |
C8—C7—H7A | 108.8 | C4—C18—H18B | 109.5 |
C6—C7—H7B | 108.8 | H18A—C18—H18B | 109.5 |
C8—C7—H7B | 108.8 | C4—C18—H18C | 109.5 |
H7A—C7—H7B | 107.7 | H18A—C18—H18C | 109.5 |
C17—C8—C7 | 107.54 (19) | H18B—C18—H18C | 109.5 |
C17—C8—C14 | 105.97 (17) | C4—C19—H19A | 109.5 |
C7—C8—C14 | 111.32 (16) | C4—C19—H19B | 109.5 |
C17—C8—C9 | 116.30 (19) | H19A—C19—H19B | 109.5 |
C7—C8—C9 | 108.42 (16) | C4—C19—H19C | 109.5 |
C14—C8—C9 | 107.31 (16) | H19A—C19—H19C | 109.5 |
C11—C9—C10 | 113.20 (16) | H19B—C19—H19C | 109.5 |
C11—C9—C8 | 113.02 (16) | C10—C20—H20A | 109.5 |
C10—C9—C8 | 115.61 (16) | C10—C20—H20B | 109.5 |
C11—C9—H9 | 104.5 | H20A—C20—H20B | 109.5 |
C10—C9—H9 | 104.5 | C10—C20—H20C | 109.5 |
C8—C9—H9 | 104.5 | H20A—C20—H20C | 109.5 |
C1—C10—C20 | 108.29 (18) | H20B—C20—H20C | 109.5 |
C1—C10—C5 | 107.33 (17) | O21—C21—O15 | 123.8 (2) |
C20—C10—C5 | 113.61 (18) | O21—C21—C22 | 125.3 (2) |
C1—C10—C9 | 108.20 (16) | O15—C21—C22 | 110.9 (2) |
C20—C10—C9 | 111.80 (17) | C21—C22—H22A | 109.5 |
C5—C10—C9 | 107.40 (16) | C21—C22—H22B | 109.5 |
C12—C11—C9 | 112.84 (18) | H22A—C22—H22B | 109.5 |
C12—C11—H11A | 109.0 | C21—C22—H22C | 109.5 |
C9—C11—H11A | 109.0 | H22A—C22—H22C | 109.5 |
C12—C11—H11B | 109.0 | H22B—C22—H22C | 109.5 |
C10—C1—C2—C3 | −56.6 (3) | C11—C9—C10—C20 | −62.7 (2) |
C1—C2—C3—C4 | 54.7 (3) | C8—C9—C10—C20 | 70.0 (2) |
C2—C3—C4—C19 | 75.4 (2) | C11—C9—C10—C5 | 172.06 (17) |
C2—C3—C4—C18 | −168.08 (19) | C8—C9—C10—C5 | −55.3 (2) |
C2—C3—C4—C5 | −50.7 (3) | C10—C9—C11—C12 | −177.40 (17) |
C19—C4—C5—C6 | 59.6 (2) | C8—C9—C11—C12 | 48.7 (2) |
C18—C4—C5—C6 | −60.6 (3) | C9—C11—C12—C13 | −49.5 (2) |
C3—C4—C5—C6 | −176.84 (19) | C11—C12—C13—C16 | −65.0 (2) |
C19—C4—C5—C10 | −71.9 (2) | C11—C12—C13—C14 | 58.9 (2) |
C18—C4—C5—C10 | 167.9 (2) | C16—C13—C14—C15 | −75.3 (2) |
C3—C4—C5—C10 | 51.7 (3) | C12—C13—C14—C15 | 165.17 (18) |
C10—C5—C6—C7 | −60.0 (2) | C16—C13—C14—C8 | 52.5 (2) |
C4—C5—C6—C7 | 165.89 (18) | C12—C13—C14—C8 | −67.0 (2) |
C5—C6—C7—C8 | 57.3 (2) | C17—C8—C14—C13 | −61.2 (2) |
C6—C7—C8—C17 | 75.4 (2) | C7—C8—C14—C13 | −177.80 (17) |
C6—C7—C8—C14 | −168.96 (17) | C9—C8—C14—C13 | 63.7 (2) |
C6—C7—C8—C9 | −51.1 (2) | C17—C8—C14—C15 | 64.5 (2) |
C17—C8—C9—C11 | 63.3 (2) | C7—C8—C14—C15 | −52.2 (2) |
C7—C8—C9—C11 | −175.42 (16) | C9—C8—C14—C15 | −170.65 (18) |
C14—C8—C9—C11 | −55.1 (2) | C21—O15—C15—C14 | −80.9 (2) |
C17—C8—C9—C10 | −69.4 (2) | C13—C14—C15—O15 | −59.3 (2) |
C7—C8—C9—C10 | 51.9 (2) | C8—C14—C15—O15 | 176.77 (16) |
C14—C8—C9—C10 | 172.21 (17) | C14—C13—C16—O16 | 154.9 (2) |
C2—C1—C10—C20 | −68.7 (2) | C12—C13—C16—O16 | −84.2 (3) |
C2—C1—C10—C5 | 54.3 (2) | C14—C13—C16—O17 | −33.4 (3) |
C2—C1—C10—C9 | 169.90 (18) | C12—C13—C16—O17 | 87.6 (2) |
C6—C5—C10—C1 | 173.53 (16) | O16—C16—O17—C17 | −163.0 (2) |
C4—C5—C10—C1 | −53.3 (2) | C13—C16—O17—C17 | 24.8 (3) |
C6—C5—C10—C20 | −66.8 (2) | C16—O17—C17—C8 | −37.0 (3) |
C4—C5—C10—C20 | 66.4 (2) | C7—C8—C17—O17 | 173.55 (16) |
C6—C5—C10—C9 | 57.4 (2) | C14—C8—C17—O17 | 54.4 (2) |
C4—C5—C10—C9 | −169.45 (18) | C9—C8—C17—O17 | −64.7 (2) |
C11—C9—C10—C1 | 56.5 (2) | C15—O15—C21—O21 | −4.3 (4) |
C8—C9—C10—C1 | −170.88 (17) | C15—O15—C21—C22 | 174.4 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
C14—H14···O17i | 1.00 | 2.49 | 3.486 (3) | 171 |
C15—H15···O21ii | 0.99 | 2.52 | 3.509 (3) | 173 |
Symmetry codes: (i) x, y+1, z; (ii) x, y−1, z. |
Experimental details
Crystal data | |
Chemical formula | C22H34O4 |
Mr | 362.49 |
Crystal system, space group | Monoclinic, C2 |
Temperature (K) | 150 |
a, b, c (Å) | 13.377 (2), 6.0824 (8), 23.834 (3) |
β (°) | 94.235 (2) |
V (Å3) | 1933.9 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 1.07 × 0.50 × 0.13 |
Data collection | |
Diffractometer | Bruker SMART APEX CCD area-detector diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5352, 2382, 2200 |
Rint | 0.133 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.049, 0.133, 0.92 |
No. of reflections | 2382 |
No. of parameters | 239 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.40, −0.27 |
Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SAINT and SHELXTL (Bruker, 2001), SIR2002 (Burla et al., 2003), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2003), enCIFer (Allen et al., 2004) and PLATON.
D—H···A | D—H | H···A | D···A | D—H···A |
C14—H14···O17i | 1.00 | 2.49 | 3.486 (3) | 171 |
C15—H15···O21ii | 0.99 | 2.52 | 3.509 (3) | 173 |
Symmetry codes: (i) x, y+1, z; (ii) x, y−1, z. |
Acknowledgements
The authors thank the EPSRC (UK) for the funding of a diffractometer. We also gratefully acknowledge financial support by the Spanish Ministry of Education and Science under a `Ramón y Cajal' research grant.
References
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© International Union of Crystallography. Prior permission is not required to reproduce short quotations, tables and figures from this article, provided the original authors and source are cited. For more information, click here.
Spongian diterpenoids are bioactive natural products isolated exclusively from sponges and shell-less molluscs (nudibranchs), which are believed to be capable of sequestering the spongian-derived metabolites from the sponges on which they feed. Most of these compounds play a key role as eco-physiological mediators and are of interest as potential therapeutic agents (Arnó, Betancur-Galvis et al., 2003).
The carbon skeleton (I) (Scheme 1), named `spongian' in accordance with IUPAC recommendations (Kazlauskas et al., 1979), was chosen as the fundamental parent structure for this family of natural compounds with the numbering depicted. Thus, spongians typically exhibit the hydrocarbon ring system (I), consisting of a steroid-like ABCD ring system containing an oxygenated group, such as a tetrahydrofuran ring, and with varying oxidation patterns on rings A–D.
The title compound, (1b), was isolated from the sponge Aplysilla rosea Barrois by Taylor & Toth (1997) and the structure (1a), in which ring D is usually a five-membered lactone typical of other members of the spongian family (Cimino et al., 1974; Karuso & Taylor, 1986; Miyamoto et al., 1996), was assigned from one-dimensional and two-dimensional 1H NMR data, high-resolution mass spectrometry and IR spectroscopy. Following our studies directed towards the synthesis of C-17-functionalized spongians (Arnó et al., 2001), we selected (1a) as a potential target compound and we readily synthesized a compound (Arnó, González & Zaragozá, 2003) whose spectroscopic data were in apparently good agreement with those reported for natural aplyroseol-14. However, a careful study of the spectroscopic data, in particular the IR and NMR spectra, indicated that the molecule contained the six-membered lactone (1b) instead of the expected five-membered one seen, for example, in 5R*,7S*,8S*,9S*,10R*,13S*,14S*)-16-oxospongian-7,17-diyl diacetate (Karuso & Taylor, 1986) or 7α-hydroxyspongian-16-one (Miyamoto et al., 1996). We supported our assignment by synthesizing the proposed structure (1a) for aplyroseol-14 and making comparisons with the published data. As expected, the synthetic compound (1a) gave spectroscopic data that, although generally similar to those reported for natural (1b), were nevertheless clearly different. Owing to the uniqueness of the carbon skeleton of (1b), together with apparent disagreement in some reported data (IR bands), a single-crystal X-ray study was carried out on synthetic (1b) in order to confirm the structural assignment. The 1H NMR spectra of synthetic (1b) and natural (1b) were found be be in excellent agreement.
A perspective view of the molecule is shown in Fig. 1. Both chemical connectivity and relative stereochemistry are in full agreement with those proposed by Arnó, González & Zaragozá (2003) for aplyroseol-14, (1b). The stereochemistry at C5 (S), C9 (R) and C10 (S) is invariant during the synthesis, but three new asymmetric centres were introduced at C8 (S), C13 (R) and C14 (R). The molecule contains a trans–anti–trans 6/6/6 tricyclic hydrocarbon group to which a six-membered lactone ring is attached at C8 and C13. All six-membered rings adopt chair conformations with axially disposed methyl or lactone substituents. However, the lactone ring (atoms C8/C14/C13/C16/O17/C17) is distorted towards a half-chair conformation; while atom C8 lies 0.734 (3) Å below the least-squares mean plane through atoms C14, C13, O17 and C17, atom C16 lies only 0.329 (3) Å above it. The acetoxymethyl group at atom C14 lies in an equatorial position. Bond lengths and angles are typical for such sterically non-strained molecules.
Molecules are linked by almost linear pairwise C—H···O interactions (Table 1 and Fig. 2). One of these interactions occurs between carbonyl atom O21 of the acetoxy group and atom H15 of the methylene group adjacent to the acetoxy group in a neighbouring molecule; the other involves methine atom H14 and lactone atom O17 in the same neighbouring molecule. The interactions link the molecules into chains running along the b axis. The C—H···O interactions contrast with the situation in analogous compounds containing hydroxy groups (Schmitz et al., 1985; Karuso et al., 1986; Miyamoto et al., 1996), where the presence of the hydroxy groups leads to O—H···O═C hydrogen bonds being the primary intermolecular contacts.