De­acetyl­cinobufalactam monohydrate

Hong-Jin Tang; Xiao-Feng Yuan; Hai-Yan Tian; Li-Jun Ruan; Ren-Wang Jiang

doi:10.1107/S1600536814010046

. 2014 May 10;70(Pt 6):o651–o652. doi: 10.1107/S1600536814010046

Deacetylcinobufalactam monohydrate

Hong-Jin Tang ^a, Xiao-Feng Yuan ^a, Hai-Yan Tian ^a, Li-Jun Ruan ^a, Ren-Wang Jiang ^a,^*

PMCID: PMC4051091 PMID: 24940236

Abstract

The title compound, C₂₄H₃₃NO₄·H₂O, the reaction product of deacetylcinobufagin with ammonium acetate, consists of three cyclohexane rings (A, B and C), one five-membered ring (D), one six-membered lactone ring (E) and an epoxide ring (F). The stereochemistry of the ring junctures are A/B cis, B/C trans, C/D cis and D/F cis. Cyclohexane rings A, B and C have normal chair conformations. The five-membered ring D adopts an envelope conformation (with the C atom bearing the lactone ring as the flap) and the lactone ring E is planar. In the crystal, hydroxy and water O—H⋯O and amine N—H⋯O hydrogen bonds involving carbonyl, hydroxy and water O-atom acceptors link the molecules into a three-dimensional network.

Related literature

For a previous isolation of deacetylcinobufagin [cinobufagin systematic name: (3β,5β,15β,16β)-16-acetoxy-3-hydroxy-14,15-epoxybufa-20,22-dienolide] see: Li et al. (2007 ▶). For the biosynthesis of deacetylcinobufagin, see: Zhan et al. (2003 ▶). For its pharmacological activity, see: Yu et al. (2008 ▶); Tian et al. (2013 ▶). For the stereochemistry of bufalin, see: Rohrer et al. (1982 ▶).

Experimental

Crystal data

C₂₄H₃₃NO₄·H₂O
M _r = 417.53
Monoclinic,
a = 8.0097 (2) Å
b = 12.1155 (4) Å
c = 11.3627 (3) Å
β = 95.077 (3)°
V = 1098.33 (5) Å³
Z = 2
Cu Kα radiation
μ = 0.71 mm⁻¹
T = 290 K
0.40 × 0.32 × 0.10 mm

Data collection

Oxford Diffraction Gemini-S Ultra sapphire CCD diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011 ▶) T _min = 0.806, T _max = 1.0
3289 measured reflections
2396 independent reflections
2261 reflections with I > 2σ(I)
R _int = 0.018

Refinement

R[F ² > 2σ(F ²)] = 0.031
wR(F ²) = 0.081
S = 1.08
2396 reflections
280 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.14 e Å⁻³
Δρ_min = −0.13 e Å⁻³

Data collection: CrysAlis PRO (Agilent, 2011 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP in SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536814010046/zs2298sup1.cif

e-70-0o651-sup1.cif^{(35.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536814010046/zs2298Isup2.hkl

e-70-0o651-Isup2.hkl^{(117.7KB, hkl)}

CCDC reference: 1000729

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1W—H1WA⋯O4ⁱ	0.93 (4)	1.79 (4)	2.710 (3)	170 (4)
O1W—H1WB⋯O3	0.80 (5)	2.07 (5)	2.867 (3)	170 (4)
N1—H1A⋯O1ⁱⁱ	0.86	2.00	2.839 (3)	165
O1—H1B⋯O1W ⁱⁱⁱ	0.82	1.90	2.690 (3)	161
O3—H3A⋯O1^iv	0.82	2.09	2.868 (2)	157

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

Acknowledgments

This work was supported by the 111 Project (No. B13038) from the Ministry of Education of the People’s Republic of China.

supplementary crystallographic information

1. Comment

Deacetylcinobufagin is a natural cardiactonic steroid which has been isolated from the skin of the toad (Li et al., 2007) and has also been biosynthesized by microbial transformation of cinobufagin (Zhan et al., 2003). Compounds of this type have shown strong cytotoxic effects against a wide range of cancer cells (Yu et al., 2008). However they also possess cardiac toxicity due to the inhibition of sodium-potassium ATPase (Tian et al., 2013). Thus structural modification of the pharmacological profile of the molecule was warranted. Recently we treated deacetylcinobufagin (isolated in our laboratory) with ammonium acetate, and a new hydrated derivative, C₂₄H₃₃O₄N . H₂O, the title compound, named deacetylcinobufalactam, was obtained after recrystallization from methanol at room temperature. We report herein the crystal structure of this compound.

The molecule of the title compound (Fig. 1) consists of three cyclohexane rings (A, B and C), one five-membered ring (D), one six-membered lactam ring (E) and an epoxide ring (F). The stereochemistry of the ring juncture is A/Bcis, B/Ctrans, C/Dcis and D/Fcis. The cyclohexane rings A, B and C have normal chair conformations. The five-membered ring (D adopts an envelope conformation with C17 displaced by -0.381 (3) Å from the mean plane of the remaining four atoms (C13, C14, C15 and C16). The lactam ring (E) and the epoxide ring (F) are planar and roughly perpendicular to each other with a dihedral angle of 96.6 (4)°. The absolute configuration determined for bufalin (Rohrer et al., 1982), a similar cardiactonic steroid, was invoked, giving the assignments of the 10 chiral centres in the title molecule as shown in Fig. 1.

In the crystal, intermolecular hydroxyl and water O—H···O hydrogen bonds to hydroxyl, carbonyl and water O-atom acceptors and a hetero-amine N—H···O_hydroxyl hydrogen bond (Table 1) link the molecules into a three-dimensional network structure (Figure 2).

2. Experimental

Deacetylcinobufagin (40.0 mg) was dissolved in DMF, then ammonium acetate (38.5 mg) was added under nitrogen protection. The mixture was stirred for three hours at 100 °C. After completion of the reaction, the mixture was poured into water and extracted with ethyl acetate. The ethyl acetate extract was washed with water to remove the solvent DMF and the excess ammonium acetate and condensed by rotary evaporation under reduced pressure. The residue was recrystallized in methanol at room temperature to afford colorless crystals (28.6 mg, yield 71.7%).