5-Fluoro-1-octanoyl­uracil

The crystal structure of 5-fluoro-1-octanoyl­uracil [5-fluoro-1-octanoyl­pyrimidine-2,4(1H,3H)-dione, C₁₂H₁₇FN₂O₃], a lipophilic prodrug of 5-fluoro­uracil, is described. The 5-fluoro­pyrimidine-2,4(1H,3H)-dione moiety is similar to the known structure of 1-acetyl-5-fluoro­uracil. The 1-octanoyl group and the 5-fluoro­uracil moiety are essentially coplanar, with the octanoyl carbonyl group oriented towards the the ring C-H group and away from the nearer ring carbonyl group. The torsion angle C-N-C-O (from the ring CH group to the octanoyl carbonyl group) of 9.2 (2)° is similar to the corresponding torsion angles reported for 1-acetyl-5-fluoro­uracil (17.3 and 1.6°) and 1,3-di­acetyl-5-fluoro­uracil (8.8°).

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and local programs.

5-fluoro-1-octanoylpyrimidine-2,4(1H,3H)-dione

Crystal data

C12H17FN2O3	F(000) = 272
Mr = 256.28	Dx = 1.347 Mg m^−3
Triclinic, P1	Melting point: 63–65°C K
a = 5.4500 (11) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.7410 (19) Å	Cell parameters from 4236 reflections
c = 12.307 (3) Å	θ = 1.0–25.4°
α = 80.27 (3)°	µ = 0.11 mm^−1
β = 85.97 (3)°	T = 173 K
γ = 79.13 (3)°	Irregular plate-like fragment, colourless
V = 631.9 (2) Å^3	0.32 × 0.20 × 0.04 mm
Z = 2

Data collection

Nonius KappaCCD diffractometer	1562 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.034
Graphite monochromator	θmax = 25.2°, θmin = 1.7°
Detector resolution: 18 pixels mm^-1	h = −6→6
ω scans at fixed χ = 55°	k = −11→11
4358 measured reflections	l = −14→14
2277 independent reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.041	H-atom parameters constrained
wR(F^2) = 0.100	w = 1/[σ^2(Fo^2) + (0.0424P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.001
2277 reflections	Δρmax = 0.21 e Å^−3
165 parameters	Δρmin = −0.20 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.048 (5)

Special details

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 > 2σ(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. The torsion angle of methyl hydrogen atoms was assigned via the SHELXL97 instruction AFIX 137.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N1	0.4938 (2)	0.88612 (13)	0.40804 (10)	0.0211 (3)
C2	0.7381 (3)	0.81445 (17)	0.38701 (13)	0.0239 (4)
O2	0.8867 (2)	0.86322 (12)	0.32137 (9)	0.0330 (3)
N3	0.7978 (2)	0.68201 (13)	0.44892 (10)	0.0245 (4)
H3	0.9447	0.6327	0.4331	0.029*
C4	0.6582 (3)	0.61694 (18)	0.53204 (13)	0.0256 (4)
O4	0.7347 (2)	0.49871 (11)	0.58329 (9)	0.0331 (3)
C5	0.4169 (3)	0.70182 (17)	0.55021 (13)	0.0252 (4)
F5	0.26729 (17)	0.64464 (10)	0.63032 (7)	0.0384 (3)
C6	0.3404 (3)	0.82681 (17)	0.49141 (12)	0.0240 (4)
H6	0.1780	0.8775	0.5060	0.029*
O7	0.1924 (2)	1.08259 (11)	0.38610 (8)	0.0304 (3)
C7	0.3881 (3)	1.02401 (17)	0.34910 (13)	0.0235 (4)
C8	0.5234 (3)	1.08731 (17)	0.24820 (12)	0.0270 (4)
H8A	0.5838	1.0138	0.2012	0.032*
H8B	0.6708	1.1199	0.2706	0.032*
C9	0.3553 (3)	1.21184 (17)	0.18167 (13)	0.0288 (4)
H9A	0.2514	1.2691	0.2330	0.035*
H9B	0.4609	1.2729	0.1351	0.035*
C10	0.1859 (3)	1.16378 (17)	0.10863 (13)	0.0312 (4)
H10A	0.0816	1.1025	0.1557	0.037*
H10B	0.2909	1.1058	0.0581	0.037*
C11	0.0148 (3)	1.28433 (17)	0.04029 (13)	0.0319 (4)
H11A	−0.1031	1.3361	0.0907	0.038*
H11B	0.1173	1.3513	−0.0009	0.038*
C12	−0.1340 (3)	1.23524 (17)	−0.04105 (13)	0.0322 (5)
H12A	−0.0157	1.1829	−0.0910	0.039*
H12B	−0.2364	1.1684	0.0004	0.039*
C13	−0.3045 (3)	1.35377 (18)	−0.11009 (13)	0.0362 (5)
H13A	−0.2018	1.4180	−0.1548	0.043*
H13B	−0.4180	1.4091	−0.0604	0.043*
C14	−0.4600 (3)	1.3013 (2)	−0.18645 (14)	0.0421 (5)
H14A	−0.3490	1.2472	−0.2365	0.063*
H14B	−0.5645	1.3824	−0.2295	0.063*
H14C	−0.5669	1.2404	−0.1427	0.063*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0153 (8)	0.0227 (8)	0.0238 (7)	0.0000 (6)	0.0011 (6)	−0.0041 (6)
C2	0.0201 (10)	0.0266 (10)	0.0254 (9)	−0.0017 (8)	−0.0020 (8)	−0.0076 (8)
O2	0.0213 (7)	0.0362 (8)	0.0360 (7)	−0.0001 (6)	0.0051 (6)	0.0012 (6)
N3	0.0166 (7)	0.0234 (8)	0.0307 (8)	0.0022 (6)	0.0026 (6)	−0.0041 (7)
C4	0.0216 (10)	0.0259 (10)	0.0291 (10)	−0.0022 (8)	−0.0012 (8)	−0.0061 (9)
O4	0.0284 (7)	0.0263 (7)	0.0393 (7)	0.0022 (6)	0.0018 (6)	0.0009 (6)
C5	0.0208 (9)	0.0272 (10)	0.0262 (9)	−0.0048 (8)	0.0055 (8)	−0.0029 (8)
F5	0.0291 (6)	0.0337 (6)	0.0444 (6)	−0.0009 (5)	0.0108 (5)	0.0056 (5)
C6	0.0169 (9)	0.0278 (10)	0.0272 (9)	−0.0012 (8)	0.0015 (7)	−0.0084 (8)
O7	0.0242 (7)	0.0291 (7)	0.0335 (7)	0.0030 (6)	0.0038 (5)	−0.0030 (6)
C7	0.0209 (9)	0.0242 (10)	0.0255 (9)	−0.0021 (8)	−0.0041 (8)	−0.0051 (8)
C8	0.0258 (10)	0.0266 (10)	0.0275 (9)	−0.0026 (8)	0.0000 (7)	−0.0038 (8)
C9	0.0286 (10)	0.0284 (10)	0.0266 (9)	−0.0026 (8)	0.0016 (8)	0.0000 (8)
C10	0.0321 (10)	0.0282 (10)	0.0314 (10)	−0.0039 (8)	−0.0015 (8)	−0.0009 (8)
C11	0.0329 (10)	0.0315 (10)	0.0300 (10)	−0.0036 (8)	−0.0020 (8)	−0.0037 (8)
C12	0.0318 (10)	0.0329 (11)	0.0309 (10)	−0.0038 (9)	0.0003 (8)	−0.0052 (8)
C13	0.0393 (11)	0.0367 (11)	0.0322 (10)	−0.0060 (9)	−0.0063 (9)	−0.0029 (9)
C14	0.0409 (12)	0.0516 (13)	0.0350 (11)	−0.0102 (10)	−0.0057 (9)	−0.0063 (9)

Geometric parameters (Å, º)

N1—C6	1.3950 (19)	C5—F5	1.3490 (18)
N1—C2	1.410 (2)	O7—C7	1.2084 (18)
N1—C7	1.449 (2)	C7—C8	1.500 (2)
C2—O2	1.2074 (18)	C8—C9	1.527 (2)
C2—N3	1.3766 (19)	C9—C10	1.517 (2)
N3—C4	1.3714 (19)	C10—C11	1.523 (2)
C4—O4	1.2282 (18)	C11—C12	1.520 (2)
C4—C5	1.440 (2)	C12—C13	1.514 (2)
C5—C6	1.316 (2)	C13—C14	1.517 (2)
C6—N1—C2	120.36 (14)	F5—C5—C4	116.15 (14)
C6—N1—C7	115.90 (13)	C5—C6—N1	121.15 (15)
C2—N1—C7	123.71 (13)	O7—C7—N1	116.73 (14)
O2—C2—N3	121.57 (14)	O7—C7—C8	123.48 (15)
O2—C2—N1	124.02 (15)	N1—C7—C8	119.78 (14)
N3—C2—N1	114.41 (14)	C7—C8—C9	111.77 (14)
C4—N3—C2	128.42 (14)	C10—C9—C8	112.19 (13)
O4—C4—N3	122.42 (15)	C9—C10—C11	114.19 (14)
O4—C4—C5	125.06 (16)	C12—C11—C10	113.52 (14)
N3—C4—C5	112.53 (15)	C13—C12—C11	114.28 (14)
C6—C5—F5	120.89 (14)	C12—C13—C14	113.15 (14)
C6—C5—C4	122.95 (16)