Methyl 3-[(1-adamantylcarbon­yloxy)amino­carbon­yl]propanoate

Liu, J.; Clegg, J.K.; Codd, R.

doi:10.1107/S1600536809024210

Methyl 3-[(1-adamantylcarbonyloxy)aminocarbonyl]propanoate

In the title compound, C₁₆H₂₃NO₅, the H—N—O—C torsion angle is 98.6 (1)°, which is of a similar magnitude to other N,O-diacylhydroxylamines. The N—O distance is 1.4029 (14) Å, which is similar to the N—O distance in other N,O-diacylhydroxylamines. In the crystal, intermolecular N—H

O hydrogen bonds generate chains of molecules.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536809024210/bg2266sup1.cif Contains datablocks global, I
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536809024210/bg2266Isup2.hkl Contains datablock I

CCDC reference: 744281

checkCIF report

Key indicators

Single-crystal X-ray study
T = 150 K
Mean (C-C) = 0.002 Å
R factor = 0.048
wR factor = 0.132
Data-to-parameter ratio = 22.9

checkCIF/PLATON results

No syntax errors found



Alert level C
ABSTM02_ALERT_3_C  The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
            Tmin and Tmax reported:      0.851     0.981
            Tmin(prime) and Tmax expected:      0.971     0.986
            RR(prime) =      0.881
            Please check that your absorption correction is appropriate.
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C6     --  C7      ..       6.13 su
PLAT061_ALERT_4_C Tmax/Tmin Range Test RR' too Large .............       0.88

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

Comment top

O-Adamantanecarboxoyl-N-4-methoxy-4-oxobutanoyl-hydroxylamine (I) (Fig 1.) was prepared in our laboratory as part of our program in understanding resonance and tautomerism in biologically relevant molecules such as N,O-diacylhydroxylamines and hydroxamic acids. The torsion angle defined by H—N—O—C in each of N,O-diacetylhydroxylamine (-99.0 (1) °), N-acetyl-O-benzoylhydroxylamine (-101.3 (1) °), and N-benzoyl-O-acetylhydroxylamine (-94.1 (1) °) is negative, which is distinct from the analogous angle in N,O-dibenzoylhydroxylamine determined by the same group, which is positive (99.7 (1) °) (Schraml et al., 2004). The positive torsion angle defined by H1—N1—O4—C6 in I is 98.6 (1) °, which is akin to N,O-dibenzoylhydroxylamine. The N—O distance in I (N1—O4 = 1.4029 (14) Å) is similar to the N—O distance in other N,O-diacylhydroxylamines as cited above. Intermolecular hydrogen bonds exist in I between respective amide groups, with H1···O3 = 1.87 Å (Table 1) forming an infinite one-dimensional polymer extending along the c-axis (Fig 2.).

Related literature top

For the biological activity of compounds related to N,O-diacylhydroxylamines, see: Pelto & Pratt (2008). For linear N,O-diacylhydroxylamines, see: Göttlicher & Ochsenreiter (1974); Schraml et al. (2004); Baert et al. (1984); Masui et al. (1983); Grassi et al. (2002); Buscemi et al. (2006). For cyclic N,O-diacylhydroxylamines, see: Kongprakaiwoot et al. (2008). For a precursor of the title compound, see: Liu et al. (2009).

Experimental top

O-Adamantanecarboxoyl-N-4-methoxy-4-oxobutanoyl-hydroxylamine (I) was isolated from a methanol solution (14 ml) containing adamantane-1-carboxylate-2,5-pyrrolidinedione (0.25 g, 0.89 mmol) (Liu, et al., 2009) and NaOH (0.018 g, 0.45 mmol). The product was dried in vacuo; colourless crystals of I appeared after approximately 1 month from a 4.5 mg mL^-1 solution of I in ethanol:water (7:3).

Computing details top

Data collection: APEX2 (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT and XPREP (Bruker, 2003); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997), WinGX32 (Farrugia, 1999), POV-RAY (Cason, 2002) and WebLab ViewerPro (Molecular Simulations, 2000); software used to prepare material for publication: enCIFer (Allen et al., 2004).

Figures top

	Fig. 1. ORTEP representation of I shown with 50% probability ellipsoids.
	Fig. 2. A schematic representation of the one dimenisonal polymer formed through hydrogen bonding interactions in I. Dashed lines indicate hydrogen bonds.

Methyl 3-[(1-adamantylcarbonyloxy)aminocarbonyl]propanoate top

Crystal data top

C₁₆H₂₃NO₅	F(000) = 1328
M_r = 309.35	D_x = 1.296 Mg m⁻³
Orthorhombic, Pccn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ab 2ac	Cell parameters from 3869 reflections
a = 15.7837 (5) Å	θ = 2.8–30.0°
b = 21.0715 (7) Å	µ = 0.10 mm⁻¹
c = 9.5341 (3) Å	T = 150 K
V = 3170.91 (18) Å³	Block, colourless
Z = 8	0.30 × 0.20 × 0.15 mm

Data collection top

Bruker APEXII-FR591 diffractometer	4586 independent reflections
Radiation source: rotating anode	2890 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.036
ω+ϕ scans	θ_max = 30.0°, θ_min = 3.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 2007)	h = −22→22
T_min = 0.851, T_max = 0.981	k = −26→29
22952 measured reflections	l = −13→11

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.132	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.0599P)² + 0.4178P] where P = (F_o² + 2F_c²)/3
4586 reflections	(Δ/σ)_max < 0.001
200 parameters	Δρ_max = 0.25 e Å⁻³
0 restraints	Δρ_min = −0.26 e Å⁻³

Crystal data top

C₁₆H₂₃NO₅	V = 3170.91 (18) Å³
M_r = 309.35	Z = 8
Orthorhombic, Pccn	Mo Kα radiation
a = 15.7837 (5) Å	µ = 0.10 mm⁻¹
b = 21.0715 (7) Å	T = 150 K
c = 9.5341 (3) Å	0.30 × 0.20 × 0.15 mm

Data collection top

Bruker APEXII-FR591 diffractometer	4586 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2007)	2890 reflections with I > 2σ(I)
T_min = 0.851, T_max = 0.981	R_int = 0.036
22952 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.048	0 restraints
wR(F²) = 0.132	H-atom parameters constrained
S = 1.04	Δρ_max = 0.25 e Å⁻³
4586 reflections	Δρ_min = −0.26 e Å⁻³
200 parameters

Special details top

Experimental. The crystal was coated in Exxon Paratone N hydrocarbon oil and mounted on a thin mohair fibre attached to a copper pin. Upon mounting on the diffractometer, the crystal was quenched to 150(K) under a cold nitrogen gas stream supplied by an Oxford Cryosystems Cryostream and data were collected at this temperature.

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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	−0.10511 (9)	0.03188 (7)	0.34190 (19)	0.0397 (4)
H1A	−0.1286	0.0521	0.4259	0.060*
H1B	−0.1195	−0.0134	0.3422	0.060*
H1C	−0.1289	0.0520	0.2580	0.060*
C2	0.01542 (9)	0.09834 (6)	0.33007 (15)	0.0282 (3)
C3	0.11059 (9)	0.09992 (7)	0.32346 (18)	0.0347 (3)
H3A	0.1293	0.0852	0.2299	0.042*
H3B	0.1339	0.0704	0.3944	0.042*
C4	0.14536 (9)	0.16607 (7)	0.34972 (19)	0.0395 (4)
H4A	0.1174	0.1965	0.2855	0.047*
H4B	0.1321	0.1790	0.4471	0.047*
C5	0.24014 (10)	0.16868 (7)	0.32743 (19)	0.0381 (4)
C6	0.41331 (9)	0.12429 (6)	0.41915 (16)	0.0285 (3)
C7	0.50576 (8)	0.13370 (5)	0.38462 (14)	0.0217 (3)
C8	0.51335 (8)	0.13881 (6)	0.22281 (15)	0.0264 (3)
H8A	0.4889	0.1005	0.1782	0.032*
H8B	0.4816	0.1763	0.1890	0.032*
C9	0.60700 (8)	0.14499 (6)	0.18337 (15)	0.0272 (3)
H9	0.6124	0.1480	0.0791	0.033*
C10	0.64442 (8)	0.20472 (6)	0.25077 (15)	0.0277 (3)
H10A	0.7048	0.2090	0.2240	0.033*
H10B	0.6137	0.2427	0.2167	0.033*
C11	0.63684 (8)	0.20033 (6)	0.40991 (15)	0.0271 (3)
H11	0.6612	0.2395	0.4533	0.032*
C12	0.54299 (8)	0.19452 (6)	0.45073 (16)	0.0269 (3)
H12A	0.5114	0.2321	0.4169	0.032*
H12B	0.5375	0.1926	0.5541	0.032*
C13	0.55512 (8)	0.07550 (6)	0.43587 (16)	0.0279 (3)
H13A	0.5313	0.0366	0.3930	0.034*
H13B	0.5499	0.0718	0.5390	0.034*
C14	0.64869 (9)	0.08217 (6)	0.39547 (17)	0.0321 (3)
H14	0.6808	0.0442	0.4292	0.039*
C15	0.68529 (9)	0.14227 (7)	0.46296 (18)	0.0358 (4)
H15A	0.6804	0.1394	0.5663	0.043*
H15B	0.7460	0.1463	0.4388	0.043*
C16	0.65534 (9)	0.08664 (6)	0.23537 (17)	0.0341 (4)
H16A	0.7156	0.0898	0.2075	0.041*
H16B	0.6313	0.0479	0.1922	0.041*
N1	0.28451 (7)	0.17669 (6)	0.44376 (15)	0.0376 (3)
H1	0.2595	0.1786	0.5262	0.045*
O1	−0.01378 (6)	0.03915 (5)	0.34139 (12)	0.0391 (3)
O2	−0.02969 (6)	0.14408 (5)	0.32255 (14)	0.0420 (3)
O3	0.27389 (7)	0.16496 (7)	0.21147 (14)	0.0595 (4)
O4	0.37279 (6)	0.18202 (4)	0.43133 (12)	0.0349 (3)
O5	0.37653 (7)	0.07535 (5)	0.43361 (14)	0.0506 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0367 (8)	0.0359 (7)	0.0464 (10)	−0.0018 (6)	0.0100 (8)	−0.0004 (7)
C2	0.0327 (7)	0.0296 (6)	0.0223 (7)	0.0045 (5)	0.0017 (6)	−0.0017 (6)
C3	0.0298 (7)	0.0359 (7)	0.0384 (9)	0.0084 (6)	0.0016 (7)	−0.0012 (6)
C4	0.0256 (7)	0.0431 (8)	0.0497 (11)	0.0040 (6)	−0.0011 (7)	−0.0097 (7)
C5	0.0289 (7)	0.0449 (8)	0.0406 (10)	0.0021 (6)	0.0015 (8)	−0.0026 (7)
C6	0.0271 (7)	0.0301 (6)	0.0281 (8)	−0.0026 (5)	0.0018 (6)	0.0000 (6)
C7	0.0217 (6)	0.0227 (6)	0.0206 (7)	−0.0040 (4)	0.0008 (6)	0.0009 (5)
C8	0.0281 (7)	0.0299 (6)	0.0211 (7)	−0.0070 (5)	−0.0028 (6)	0.0010 (5)
C9	0.0313 (7)	0.0299 (6)	0.0203 (7)	−0.0075 (5)	0.0042 (6)	0.0012 (5)
C10	0.0273 (6)	0.0239 (6)	0.0318 (9)	−0.0060 (5)	0.0018 (6)	0.0058 (5)
C11	0.0270 (6)	0.0253 (6)	0.0289 (8)	−0.0078 (5)	−0.0055 (6)	−0.0005 (5)
C12	0.0305 (7)	0.0268 (6)	0.0234 (8)	−0.0031 (5)	−0.0018 (6)	−0.0027 (5)
C13	0.0306 (7)	0.0238 (6)	0.0294 (8)	−0.0035 (5)	0.0021 (7)	0.0074 (5)
C14	0.0264 (7)	0.0267 (6)	0.0433 (10)	0.0033 (5)	−0.0003 (7)	0.0103 (6)
C15	0.0259 (7)	0.0435 (8)	0.0382 (9)	−0.0039 (6)	−0.0099 (7)	0.0099 (7)
C16	0.0304 (7)	0.0259 (6)	0.0459 (10)	−0.0028 (5)	0.0123 (7)	−0.0021 (6)
N1	0.0215 (6)	0.0512 (7)	0.0401 (8)	0.0015 (5)	0.0037 (6)	−0.0063 (6)
O1	0.0342 (5)	0.0295 (5)	0.0538 (8)	0.0035 (4)	0.0041 (5)	−0.0012 (5)
O2	0.0312 (5)	0.0327 (5)	0.0621 (8)	0.0069 (4)	0.0012 (6)	0.0032 (5)
O3	0.0365 (7)	0.1062 (11)	0.0358 (8)	0.0027 (7)	0.0009 (6)	0.0004 (7)
O4	0.0213 (5)	0.0350 (5)	0.0485 (7)	0.0011 (4)	0.0008 (5)	−0.0027 (5)
O5	0.0314 (5)	0.0362 (6)	0.0841 (10)	−0.0085 (4)	0.0154 (6)	0.0045 (6)

Geometric parameters (Å, º) top

C1—O1	1.4498 (17)	C9—C16	1.5296 (19)
C1—H1A	0.9800	C9—C10	1.5316 (18)
C1—H1B	0.9800	C9—H9	1.0000
C1—H1C	0.9800	C10—C11	1.525 (2)
C2—O2	1.2005 (16)	C10—H10A	0.9900
C2—O1	1.3340 (16)	C10—H10B	0.9900
C2—C3	1.5038 (19)	C11—C15	1.5289 (19)
C3—C4	1.519 (2)	C11—C12	1.5364 (18)
C3—H3A	0.9900	C11—H11	1.0000
C3—H3B	0.9900	C12—H12A	0.9900
C4—C5	1.512 (2)	C12—H12B	0.9900
C4—H4A	0.9900	C13—C14	1.5327 (19)
C4—H4B	0.9900	C13—H13A	0.9900
C5—O3	1.230 (2)	C13—H13B	0.9900
C5—N1	1.322 (2)	C14—C16	1.533 (2)
C6—O5	1.1913 (16)	C14—C15	1.533 (2)
C6—O4	1.3792 (16)	C14—H14	1.0000
C6—C7	1.5090 (18)	C15—H15A	0.9900
C7—C13	1.5329 (17)	C15—H15B	0.9900
C7—C12	1.5443 (17)	C16—H16A	0.9900
C7—C8	1.5510 (19)	C16—H16B	0.9900
C8—C9	1.5308 (18)	N1—O4	1.4029 (14)
C8—H8A	0.9900	N1—H1	0.8800
C8—H8B	0.9900

O1—C1—H1A	109.5	C11—C10—H10A	109.7
O1—C1—H1B	109.5	C9—C10—H10A	109.7
H1A—C1—H1B	109.5	C11—C10—H10B	109.7
O1—C1—H1C	109.5	C9—C10—H10B	109.7
H1A—C1—H1C	109.5	H10A—C10—H10B	108.2
H1B—C1—H1C	109.5	C10—C11—C15	109.78 (12)
O2—C2—O1	123.41 (13)	C10—C11—C12	109.42 (11)
O2—C2—C3	124.90 (13)	C15—C11—C12	109.55 (11)
O1—C2—C3	111.67 (11)	C10—C11—H11	109.4
C2—C3—C4	111.98 (11)	C15—C11—H11	109.4
C2—C3—H3A	109.2	C12—C11—H11	109.4
C4—C3—H3A	109.2	C11—C12—C7	109.24 (11)
C2—C3—H3B	109.2	C11—C12—H12A	109.8
C4—C3—H3B	109.2	C7—C12—H12A	109.8
H3A—C3—H3B	107.9	C11—C12—H12B	109.8
C5—C4—C3	111.57 (12)	C7—C12—H12B	109.8
C5—C4—H4A	109.3	H12A—C12—H12B	108.3
C3—C4—H4A	109.3	C7—C13—C14	109.65 (10)
C5—C4—H4B	109.3	C7—C13—H13A	109.7
C3—C4—H4B	109.3	C14—C13—H13A	109.7
H4A—C4—H4B	108.0	C7—C13—H13B	109.7
O3—C5—N1	122.19 (14)	C14—C13—H13B	109.7
O3—C5—C4	123.55 (15)	H13A—C13—H13B	108.2
N1—C5—C4	114.25 (15)	C13—C14—C16	108.77 (12)
O5—C6—O4	121.84 (12)	C13—C14—C15	109.46 (12)
O5—C6—C7	127.62 (12)	C16—C14—C15	109.96 (11)
O4—C6—C7	110.54 (10)	C13—C14—H14	109.5
C6—C7—C13	108.46 (10)	C16—C14—H14	109.5
C6—C7—C12	112.83 (11)	C15—C14—H14	109.5
C13—C7—C12	109.90 (11)	C11—C15—C14	109.49 (11)
C6—C7—C8	107.50 (11)	C11—C15—H15A	109.8
C13—C7—C8	109.47 (11)	C14—C15—H15A	109.8
C12—C7—C8	108.61 (10)	C11—C15—H15B	109.8
C9—C8—C7	108.95 (11)	C14—C15—H15B	109.8
C9—C8—H8A	109.9	H15A—C15—H15B	108.2
C7—C8—H8A	109.9	C9—C16—C14	109.75 (11)
C9—C8—H8B	109.9	C9—C16—H16A	109.7
C7—C8—H8B	109.9	C14—C16—H16A	109.7
H8A—C8—H8B	108.3	C9—C16—H16B	109.7
C16—C9—C8	109.49 (10)	C14—C16—H16B	109.7
C16—C9—C10	109.40 (12)	H16A—C16—H16B	108.2
C8—C9—C10	109.83 (11)	C5—N1—O4	117.73 (13)
C16—C9—H9	109.4	C5—N1—H1	121.1
C8—C9—H9	109.4	O4—N1—H1	121.1
C10—C9—H9	109.4	C2—O1—C1	116.27 (11)
C11—C10—C9	109.72 (10)	C6—O4—N1	113.40 (10)

O2—C2—C3—C4	17.1 (2)	C13—C7—C12—C11	58.97 (15)
O1—C2—C3—C4	−164.72 (13)	C8—C7—C12—C11	−60.76 (14)
C2—C3—C4—C5	−173.84 (14)	C6—C7—C13—C14	177.11 (12)
C3—C4—C5—O3	70.9 (2)	C12—C7—C13—C14	−59.12 (15)
C3—C4—C5—N1	−110.41 (16)	C8—C7—C13—C14	60.09 (14)
O5—C6—C7—C13	−26.1 (2)	C7—C13—C14—C16	−60.43 (14)
O4—C6—C7—C13	154.74 (12)	C7—C13—C14—C15	59.74 (16)
O5—C6—C7—C12	−148.06 (16)	C10—C11—C15—C14	−59.45 (15)
O4—C6—C7—C12	32.74 (16)	C12—C11—C15—C14	60.73 (16)
O5—C6—C7—C8	92.22 (18)	C13—C14—C15—C11	−60.58 (16)
O4—C6—C7—C8	−86.97 (13)	C16—C14—C15—C11	58.86 (15)
C6—C7—C8—C9	−177.12 (10)	C8—C9—C16—C14	−61.11 (14)
C13—C7—C8—C9	−59.50 (12)	C10—C9—C16—C14	59.30 (14)
C12—C7—C8—C9	60.50 (13)	C13—C14—C16—C9	60.84 (13)
C7—C8—C9—C16	59.84 (14)	C15—C14—C16—C9	−59.02 (14)
C7—C8—C9—C10	−60.31 (13)	O3—C5—N1—O4	1.1 (2)
C16—C9—C10—C11	−59.98 (14)	C4—C5—N1—O4	−177.63 (12)
C8—C9—C10—C11	60.21 (14)	O2—C2—O1—C1	1.0 (2)
C9—C10—C11—C15	60.21 (14)	C3—C2—O1—C1	−177.17 (13)
C9—C10—C11—C12	−60.05 (13)	O5—C6—O4—N1	−7.7 (2)
C10—C11—C12—C7	60.71 (13)	C7—C6—O4—N1	171.54 (11)
C15—C11—C12—C7	−59.69 (15)	C5—N1—O4—C6	−81.34 (16)
C6—C7—C12—C11	−179.84 (11)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O3ⁱ	0.88	1.87	2.7250 (19)	165

Symmetry code: (i) −x+1/2, y, z+1/2.

Experimental details

Crystal data
Chemical formula	C₁₆H₂₃NO₅
M_r	309.35
Crystal system, space group	Orthorhombic, Pccn
Temperature (K)	150
a, b, c (Å)	15.7837 (5), 21.0715 (7), 9.5341 (3)
V (Å³)	3170.91 (18)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.30 × 0.20 × 0.15

Data collection
Diffractometer	Bruker APEXII-FR591 diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2007)
T_min, T_max	0.851, 0.981
No. of measured, independent and observed [I > 2σ(I)] reflections	22952, 4586, 2890
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.704

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.048, 0.132, 1.04
No. of reflections	4586
No. of parameters	200
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.25, −0.26

Computer programs: APEX2 (Bruker, 2003), SAINT (Bruker, 2003), SAINT and XPREP (Bruker, 2003), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), WinGX32 (Farrugia, 1999), POV-RAY (Cason, 2002) and WebLab ViewerPro (Molecular Simulations, 2000), enCIFer (Allen et al., 2004).