Molecular Structure of Methyl 1-Isopropenyl- 5a,5b,8,8,11a-Pentamethyl-9-OXO-10-[(E)-1-Phenylmethylidene] Perhydrocyclopent [a]Chrysene-3a-Carboxylate

Article abstract of DOI:10.1007/s10947-010-0122-z

The molecular structure of methyl 1-isopropenyl-5a,5b,8,8,11a-pentamethyl-9-oxo-10-[(E)-1phenylmethylidene]perhydrocyclopent[a]chrysene-3a-carboxylate II is determined. Compound II C₃₈H₅₂O₃ crystallizes in the non-centrosy

Full text of DOI:10.1007/s10947-010-0122-z

Journal of Structural Chemistry. Vol. 51, No. 4, pp. 802-804, 2010
Original Russian Text Copyright © 2010 by O. B. Kazakova, N. I. Medvedeva, E. V. Salimova, and K. Yu. Suponitskii
MOLECULAR STRUCTURE OF METHYL 1-ISOPROPENYL-
5a,5b,8,8,11a-PENTAMETHYL-9-OXO-10-[(E)-
1-PHENYLMETHYLIDENE] PERHYDROCYCLOPENT
[a]CHRYSENE-3a-CARBOXYLATE
O. B. Kazakova,1 N. I. Medvedeva,1 E. V. Salimova,1
and K. Yu. Suponitskii2
UDC 547.824:542.91:548.737
The molecular structure of methyl 1-isopropenyl-5a,5b,8,8,11a-pentamethyl-9-oxo-10-[(E)-1-
phenylmethylidene]perhydrocyclopent[a]chrysene-3a-carboxylate II is determined. Compound II ꢀ38H52O3
crystallizes in the non-centrosymmetric P21 space group with the cell parameters: ꢀ = 11.4450(8) Å,
b = 11.1995(8) Å, c = 12.5179(9) Å, ꢀ = 93.984(2)°.
Keywords:
methyl
1-isopropenyl-5a,5b,8,8,11a-pentamethyl-9-oxo-10-[(E)-1-phenylmethylidene]
perhydrocyclopent[a]chrysene-3a-carboxylate, single crystal X-ray diffraction.
2-Benzylidenetriterpenoids exhibit valuable pharmacologic properties; these compounds are used in the synthesis of
heterocycles annulated with the ring A [1, 2]. Ozone treatment of 2-benzylidenesteroids of the androstane series is a short way to
2,3-diketones [3]. The literature contains no information on the structural determination of 2-benzylidenetriterpenoids and
steroids by single crystal X-ray diffraction. This paper presents the synthesis and molecular structure of methyl 1-isopropenyl-
5a,5b,8,8,11a-pentamethyl-9-oxo-10-[(E)-1-phenylmethylidene]perhydrocyclopent[a]chrysene-3a-carboxylate II.
Experimental.
Synthesis
of
methyl
1-isopropenyl-5a,5b,8,8,11a-pentamethyl-9-oxo-10-[(E)-1-
phenylmethylidene]perhydrocyclopent[a]chrysene-3a-carboxylate II (Fig. 1). 2.6 mmol of benzaldehyde and 5 ml of
40% Kꢁꢂ solution in ethanol were added under stirring and cooling (ꢁ10ꢂC) to the solution of 2 mmol (0.88 g) betulonic
acid methyl ether I in 10 ml ethanol. The mixture was kept for 30 min at this temperature, 24 h at room temperature and then
poured into 50 ml of 5% HCl solution; the residue was filtered, washed with water, air dried, and purified by column
chromatography on aluminium oxide; the eluent was benzene; the yield was 0.97 g (87%). The crystals for X-ray diffraction
were obtained by slow crystallization of the substance from benzene at room temperature followed by drying in vacuum.
1
Found, %: ꢀ 81.96, ꢂ 9.30, ꢀ38ꢂ52ꢁ3. Calculated, %: C 81.97, H 9.41. Rf 0,80. ꢁm 202-204ꢂC. The ꢂ NMR spectrum
(ꢀDCl3), ꢃ, ppm: 0.80, 0.93, 1.00, 1.12, 1.17 5 s (15ꢂ, 5ꢀꢂ3), 1.20—1.90 m (17ꢂ, ꢀꢂ2, ꢀꢂ), 1.71 s (3ꢂ, ꢂ-30), 2.17-2.32 m
(1ꢂ, ꢂ-1), 3.65 s (3ꢂ, ꢁꢀꢂ3), 4.64 s (1ꢂ, ꢂ-28), 4.76 s (1ꢂ, ꢂ-28), 7.27-7.62 m (10ꢂ, ꢂ-arom.), 7.50 s(1ꢂ, ꢂ-32). The 13
ꢀ
NMR spectrum (ꢀDCl3), ꢃ, ppm: 14.5, 15.2, 15.6, 19.4, 20.2, 21.5, 22.2, 25.5, 29.3, 29.5, 30.5, 31.9, 32.9, 36.3, 36.7, 38.1,
40.4, 42.3, 44.3, 45.0, 46.7, 48.4, 49.2, 51.4, 52.7, 56.4, 109.4, 128.2, 128.2, 128.2, 130.1, 130.1, 134.1, 135.8, 137.1, 150.5,
176.4, 207.9.
1
The NMR spectra of13ꢀ and ꢂ were recorded on a Bruker AM-300 spectrometer (75.5 MHz and 300 MHz
respectively) with tetramethylsilane (TMS) as the internal standard. Single crystal X-ray diffraction was measured on a
1Institute of Organic Chemistry, Ufa Scientific Center, Russian Academy of Sciences; obf@anrb.ru.
2A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow. Translated from
Zhurnal Strukturnoi Khimii, Vol. 51, No. 4, pp. 827-829, July-August, 2010. Original article submitted July 15, 2009.
802
0022-4766/10/5104-0802 © 2010 Springer Science+Business Media, Inc.

Fig. 1. Synthesis scheme of methyl 1-isopropenyl-5a,5b,8,8,11a-
pentamethyl-9-oxo-10-[(E)-1-phenylmethylidene]perhydrocyclopent
[a]chrysene-3a-carboxylate II.
Fig. 2. Structure of methyl 1-isopropenyl-5a,5b,8,8,11a-pentamethyl-
9-oxo-10-[(E)-1-phenylmethylidene]perhydrocyclopent[a]chrysene-
3a-carboxylate II.
Bruker SMART APEX II diffractometer. The melting temperature was determined on a Boetius heating stage. TLC was
performed on Silufol plates (Chemapol, Czech Republic) using the 25:1 chloroform–methanol solvent system. The
substances were detected with a 10% solution of phosphotungstic acid in ethanol followed by heating at 100-120ꢂC for 2-
3 min.
Single Crystal X-Ray Diffraction of Compound II. The colorless prismatic crystals of ꢀ38ꢂ52ꢁ3 (M = 556.800)
are monoclinic; at 100 K, ꢀ = 11.4450(8) Å, b = 11.1995(8) Å, c = 12.5179(9) Å, ꢀ = 93.984(2)°, V = 1600.6(2) Å3, P21
space group, Z = 2, dx = 1.155 g/cm3. The experimental set of 21,155 reflexes was collected on a Bruker SMART APEX II
diffractometer at 100 K (ꢄꢃꢄKꢅ radiation, ꢆmax = 30.14ꢂ) from a single crystal with dimensions of 0.20ꢇ0.15ꢇ0.10 mm. The
initial array of the measured intensities was processed using the SAINT [4] and SADABS programs [5]. The structure was
solved by the direct method and refined by the full matrix LSM in an anisotropic approximation for non-hydrogen atoms
against Fh2kl . Hydrogen atoms were placed into geometrically calculated positions and refined using the riding model
(Uiso(H) = nUeq(C), where n = 1.5 for carbon atoms of methyl groups and n = 1.2 for other C atoms). We used 4942
independent reflections in the refinement (Rint = 0.0437). The refinement convergence over all independent reflections was
wR2 = 0.1113 (R1 = 0.0424 in 4278 reflections with I > 2ꢈ(I)). All the computations were made on an IBM PC using the
SHELXTL software package [6]. Atomic coordinates and temperature factors have been deposited with the Cambridge
Crystallographic Data Centre (CCDC) No. 731389; http://www.ccdc.cam.ac.uk/products/csd/request/.
803

Results and Discussion. Compound II was synthesized by the interaction of betulonic acid methyl ether I with
benzaldehyde in alcoholic alkali. The product of the reaction was purified by column chromatography on aluminium oxide
with an 87% yield. Single crystal XRD was used to determine the molecular (Fig. 2) and crystal structure of methyl
1-isopropenyl-5a,5b,8,8,11a-pentamethyl-9-oxo-10-[(E)-1-phenylmethylidene]perhydrocyclopent[a]chrysene-3a-carboxylate
II. Compound II crystallizes in the non-centrosymmetric P21 space group. The five-membered ring is characterized by
envelope conformation (with the ꢀ17 atom being out of the plane of the other four atoms at 0.647(3) Å), and the cycles B, C
and D have chair conformation, which is typical of the compounds of this class. The ring ꢂ is in distorted boat conformation.
The ꢀ10 and ꢀ3 atoms are out of the plane of the other four atoms ꢀ1, ꢀ2, ꢀ4, and ꢀ5 in the same direction at 0.769(3) Å
and 0.155(3) Å respectively. Note that the cycles similar to the ring ꢂ, i.e. with substituents forming double bonds with the
neighboring carbon atoms of the ring, are characterized by various conformations from slightly distorted chair to distorted
boat [7], and the opposite carbon atoms may be out of the planar tetragonal fragment (ꢀ1, ꢀ2, ꢀ4, and ꢀ5, in the case of the
molecule of II) both in the same and opposite directions. The bond lengths and bond angles in the structure of II are typical
of the compounds of this class [8], and the crystal structure is stabilized by common van der Waals interactions.
Conclusions. Single crystal XRD has been used for the first time to characterize the structure of methyl 1-isopropenyl-
5a,5b,8,8,11a-pentamethyl-9-oxo-10-[(E)-1-phenylmethylidene]perhydrocyclopent[a]chrysene-3a-carboxylate II.
This work was partially supported by RFBR (project No. 08-03-00868).
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