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In the title compound, C18H24N2O4, the tert-butyl and carbo­methoxy substituents on the central ring are syn with respect to each other. The conformation of the central ring is such that the C atom carrying the carbo­methoxy group lies 0.609 (2) Å out of the mean plane of the other five atoms.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802002210/om6076sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536802002210/om6076Isup2.hkl
Contains datablock I

CCDC reference: 182612

Key indicators

  • Single-crystal X-ray study
  • T = 120 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.039
  • wR factor = 0.088
  • Data-to-parameter ratio = 12.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes

REFLT_03 From the CIF: _diffrn_reflns_theta_max 30.00 From the CIF: _reflns_number_total 2780 Count of symmetry unique reflns 2800 Completeness (_total/calc) 99.29% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 0 Fraction of Friedel pairs measured 0.000 Are heavy atom types Z>Si present no Please check that the estimate of the number of Friedel pairs is correct. If it is not, please give the correct count in the _publ_section_exptl_refinement section of the submitted CIF.

Comment top

α-Amino acids are receiving increasing attention in view of their interesting chemical and biological properties, both in free forms and as constituents of peptides (Spatola, 1983). The title compound, (I), was prepared to be used as a precursor of α-alkylated aspartic acid derivatives. Similar derivatives of α-alkylated aspartic acid precursors had been synthesized before (Juaristi et al., 1998). The crystal structure of (I) was determined to prove its successful synthesis.

The tert-butyl group at C1 and the carbomethoxy group at C4 are relatively syn. The conformation of the central diazine ring is such that C4 lies 0.609 (2) Å out of the best plane of the other five atoms, which are coplanar to within a maximum deviation of -0.043 (2) Å (for C1).

Experimental top

To a solution of 1-benzoyl-2(S)-tert-butyl-(6S)-carboxyperhydropyrimidin-4-one (Juaristi et al., 1996) (2 g, 6 mmol) was added silver oxide (2.85 g, 12.3 mmol) in 100 ml of dry tetrahydrofuran under argon. The resulting mixture was stirred at ambient temperature for 30 min. Methyl iodide (1.11 ml, 18 mmol) was added, and stirring was continued for 72 h. The reaction mixture was filtered over Celite (eluting with CH2Cl2) and concentrated at reduced pressure. The product was purified by flash chromatography, at first eluting with (hexanes/ethyl acetate, 9:1) and gradually increasing the concentration of ethyl acetate (hexanes/ethyl acetate, 4:1) and finally eluting with ethyl acetate and acetic acid (ethyl acetate/acetic acid, 4:1) to give 1.47 g (74.2% yield) as a crystalline solid. Crystals were grown by evaporation from hexanes/ethyl acetate, (9:1).

Refinement top

The absolute configuration could not be determined, but was assumed to correspond to the known configuration of the starting materials. H atoms were placed in calculated positions with C—H bond distances in the range 0.95–1.00 Å and Uiso = 1.2Ueq of the attached atom (1.5 for methyl groups), and thereafter treated as riding. A torsional parameter was refined for each methyl group.

Computing details top

Data collection: COLLECT (Nonius, 2000); cell refinement: DENZO and SCALEPACK; data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. Atom-numbering scheme showing ellipsoids at the 50% probability level.
1-Benzoyl-2(S)-tert-butyl-4-methoxy-6(S)-carbomethoxy-1,2,5,6-tetrahydro- 1,3-pyrimidine top
Crystal data top
C18H24N2O4F(000) = 356
Mr = 332.39Dx = 1.227 Mg m3
Monoclinic, P21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ybCell parameters from 2391 reflections
a = 10.283 (3) Åθ = 2.5–30.0°
b = 8.124 (2) ŵ = 0.09 mm1
c = 11.757 (4) ÅT = 120 K
β = 113.673 (11)°Fragment, colorless
V = 899.5 (5) Å30.45 × 0.25 × 0.10 mm
Z = 2
Data collection top
KappaCCD (with Oxford Cryostream)
diffractometer
2368 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.025
Graphite monochromatorθmax = 30.0°, θmin = 3.3°
ω scans with κ offsetsh = 1414
8506 measured reflectionsk = 911
2780 independent reflectionsl = 1616
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.039H-atom parameters constrained
wR(F2) = 0.088 w = 1/[σ2(Fo2) + (0.0334P)2 + 0.1725P]
where P = (Fo2 + 2Fc2)/3
S = 1.03(Δ/σ)max < 0.001
2780 reflectionsΔρmax = 0.19 e Å3
223 parametersΔρmin = 0.18 e Å3
1 restraintExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.035 (4)
Crystal data top
C18H24N2O4V = 899.5 (5) Å3
Mr = 332.39Z = 2
Monoclinic, P21Mo Kα radiation
a = 10.283 (3) ŵ = 0.09 mm1
b = 8.124 (2) ÅT = 120 K
c = 11.757 (4) Å0.45 × 0.25 × 0.10 mm
β = 113.673 (11)°
Data collection top
KappaCCD (with Oxford Cryostream)
diffractometer
2368 reflections with I > 2σ(I)
8506 measured reflectionsRint = 0.025
2780 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0391 restraint
wR(F2) = 0.088H-atom parameters constrained
S = 1.03Δρmax = 0.19 e Å3
2780 reflectionsΔρmin = 0.18 e Å3
223 parameters
Special details top

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
xyzUiso*/Ueq
O10.37008 (14)0.33594 (17)0.09520 (12)0.0249 (3)
O20.50381 (16)0.7956 (2)0.44708 (15)0.0419 (4)
O30.57215 (13)0.6150 (2)0.33832 (14)0.0298 (3)
O40.01145 (13)0.70686 (18)0.24520 (12)0.0269 (3)
N10.21989 (14)0.66471 (19)0.27711 (13)0.0184 (3)
N20.24587 (16)0.5725 (2)0.08579 (14)0.0217 (3)
C10.18222 (18)0.6900 (2)0.14142 (15)0.0198 (4)
H10.07740.67150.09950.024*
C20.31471 (18)0.4502 (2)0.14657 (17)0.0200 (4)
C30.34699 (19)0.4111 (2)0.27940 (17)0.0219 (4)
H3A0.44070.35640.31770.026*
H3B0.27430.33500.28430.026*
C40.34815 (17)0.5690 (2)0.34919 (16)0.0201 (4)
H40.34120.53660.42860.024*
C50.48208 (18)0.6742 (3)0.38369 (17)0.0246 (4)
C60.2073 (2)0.8684 (2)0.10656 (18)0.0244 (4)
C70.1284 (3)0.8832 (3)0.0345 (2)0.0507 (7)
H7A0.13900.99520.06040.076*
H7B0.02740.85930.05820.076*
H7C0.16810.80450.07510.076*
C80.3640 (3)0.9064 (3)0.1444 (3)0.0523 (8)
H8A0.40770.81930.11390.078*
H8B0.41130.91220.23520.078*
H8C0.37391.01220.10860.078*
C90.1440 (2)0.9941 (3)0.1661 (2)0.0314 (5)
H9A0.19320.98750.25670.047*
H9B0.04280.97060.14160.047*
H9C0.15521.10490.13840.047*
C100.11096 (17)0.6749 (2)0.31641 (16)0.0201 (4)
C110.14387 (17)0.6545 (2)0.45231 (17)0.0207 (4)
C120.05856 (19)0.5494 (3)0.48634 (18)0.0258 (4)
H120.01200.48450.42510.031*
C130.0764 (2)0.5392 (3)0.6093 (2)0.0324 (5)
H130.01960.46550.63240.039*
C140.1769 (2)0.6361 (3)0.69869 (19)0.0316 (5)
H140.18770.62990.78270.038*
C150.2617 (2)0.7420 (3)0.66558 (18)0.0298 (4)
H150.33060.80820.72690.036*
C160.24566 (19)0.7511 (3)0.54227 (18)0.0257 (4)
H160.30410.82310.51960.031*
C170.3371 (2)0.3551 (3)0.03509 (19)0.0319 (5)
H17A0.23390.35420.08170.048*
H17B0.37940.26430.06340.048*
H17C0.37570.45990.04900.048*
C180.7014 (2)0.7111 (4)0.3683 (2)0.0425 (6)
H18A0.67640.82600.34370.064*
H18B0.75580.66630.32350.064*
H18C0.75880.70570.45790.064*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0311 (7)0.0212 (7)0.0232 (7)0.0060 (6)0.0118 (5)0.0008 (5)
O20.0381 (8)0.0500 (10)0.0418 (9)0.0215 (8)0.0205 (7)0.0257 (8)
O30.0198 (6)0.0334 (8)0.0375 (8)0.0015 (6)0.0130 (6)0.0001 (7)
O40.0194 (6)0.0334 (8)0.0247 (7)0.0026 (6)0.0054 (5)0.0029 (6)
N10.0177 (6)0.0190 (7)0.0168 (7)0.0009 (6)0.0050 (5)0.0015 (6)
N20.0239 (7)0.0198 (8)0.0205 (7)0.0018 (6)0.0079 (6)0.0004 (6)
C10.0206 (8)0.0207 (9)0.0171 (8)0.0028 (7)0.0066 (6)0.0005 (7)
C20.0204 (8)0.0179 (9)0.0211 (9)0.0015 (7)0.0078 (7)0.0030 (7)
C30.0251 (8)0.0162 (8)0.0226 (9)0.0018 (7)0.0078 (7)0.0016 (7)
C40.0202 (8)0.0206 (9)0.0178 (8)0.0019 (7)0.0058 (6)0.0007 (7)
C50.0211 (8)0.0310 (10)0.0192 (8)0.0017 (8)0.0054 (7)0.0010 (8)
C60.0296 (9)0.0191 (9)0.0254 (10)0.0039 (7)0.0121 (8)0.0054 (8)
C70.095 (2)0.0272 (12)0.0291 (12)0.0178 (13)0.0238 (13)0.0083 (10)
C80.0407 (13)0.0308 (12)0.096 (2)0.0073 (11)0.0380 (14)0.0294 (14)
C90.0407 (11)0.0190 (9)0.0355 (12)0.0027 (9)0.0162 (9)0.0007 (8)
C100.0201 (7)0.0187 (8)0.0210 (8)0.0026 (7)0.0078 (6)0.0036 (7)
C110.0193 (7)0.0203 (9)0.0228 (8)0.0021 (7)0.0089 (6)0.0006 (7)
C120.0239 (8)0.0247 (9)0.0288 (10)0.0011 (8)0.0106 (7)0.0004 (8)
C130.0372 (11)0.0301 (11)0.0377 (12)0.0002 (9)0.0233 (9)0.0067 (9)
C140.0407 (11)0.0348 (12)0.0246 (10)0.0073 (9)0.0185 (8)0.0036 (9)
C150.0326 (10)0.0331 (11)0.0230 (9)0.0005 (9)0.0104 (8)0.0054 (8)
C160.0264 (9)0.0290 (10)0.0233 (9)0.0043 (8)0.0116 (7)0.0029 (8)
C170.0388 (11)0.0342 (11)0.0270 (10)0.0067 (10)0.0179 (9)0.0015 (9)
C180.0211 (9)0.0536 (16)0.0523 (14)0.0048 (10)0.0144 (9)0.0018 (12)
Geometric parameters (Å, º) top
O1—C21.351 (2)C8—H8A0.9800
O1—C171.438 (2)C8—H8B0.9800
O2—C51.202 (3)C8—H8C0.9800
O3—C51.330 (2)C9—H9A0.9800
O3—C181.457 (3)C9—H9B0.9800
O4—C101.227 (2)C9—H9C0.9800
N1—C101.375 (2)C10—C111.504 (2)
N1—C41.471 (2)C11—C161.393 (3)
N1—C11.497 (2)C11—C121.393 (3)
N2—C21.262 (2)C12—C131.384 (3)
N2—C11.453 (2)C12—H120.9500
C1—C61.555 (3)C13—C141.385 (3)
C1—H11.0000C13—H130.9500
C2—C31.495 (3)C14—C151.387 (3)
C3—C41.520 (3)C14—H140.9500
C3—H3A0.9900C15—C161.394 (3)
C3—H3B0.9900C15—H150.9500
C4—C51.530 (3)C16—H160.9500
C4—H41.0000C17—H17A0.9800
C6—C81.521 (3)C17—H17B0.9800
C6—C91.524 (3)C17—H17C0.9800
C6—C71.530 (3)C18—H18A0.9800
C7—H7A0.9800C18—H18B0.9800
C7—H7B0.9800C18—H18C0.9800
C7—H7C0.9800
C2—O1—C17116.11 (15)H8A—C8—H8B109.5
C5—O3—C18115.06 (18)C6—C8—H8C109.5
C10—N1—C4120.07 (14)H8A—C8—H8C109.5
C10—N1—C1116.92 (13)H8B—C8—H8C109.5
C4—N1—C1118.36 (13)C6—C9—H9A109.5
C2—N2—C1120.94 (16)C6—C9—H9B109.5
N2—C1—N1114.76 (14)H9A—C9—H9B109.5
N2—C1—C6109.94 (15)C6—C9—H9C109.5
N1—C1—C6114.18 (14)H9A—C9—H9C109.5
N2—C1—H1105.7H9B—C9—H9C109.5
N1—C1—H1105.7O4—C10—N1122.29 (16)
C6—C1—H1105.7O4—C10—C11118.67 (16)
N2—C2—O1121.93 (16)N1—C10—C11118.97 (14)
N2—C2—C3126.69 (17)C16—C11—C12119.67 (17)
O1—C2—C3111.38 (15)C16—C11—C10121.66 (16)
C2—C3—C4109.57 (15)C12—C11—C10118.26 (16)
C2—C3—H3A109.8C13—C12—C11120.08 (18)
C4—C3—H3A109.8C13—C12—H12120.0
C2—C3—H3B109.8C11—C12—H12120.0
C4—C3—H3B109.8C12—C13—C14120.3 (2)
H3A—C3—H3B108.2C12—C13—H13119.8
N1—C4—C3108.90 (13)C14—C13—H13119.8
N1—C4—C5111.16 (15)C13—C14—C15120.01 (19)
C3—C4—C5115.17 (15)C13—C14—H14120.0
N1—C4—H4107.1C15—C14—H14120.0
C3—C4—H4107.1C14—C15—C16119.99 (19)
C5—C4—H4107.1C14—C15—H15120.0
O2—C5—O3123.98 (18)C16—C15—H15120.0
O2—C5—C4123.09 (17)C11—C16—C15119.91 (18)
O3—C5—C4112.92 (17)C11—C16—H16120.0
C8—C6—C9109.10 (19)C15—C16—H16120.0
C8—C6—C7109.9 (2)O1—C17—H17A109.5
C9—C6—C7107.86 (17)O1—C17—H17B109.5
C8—C6—C1112.36 (16)H17A—C17—H17B109.5
C9—C6—C1110.87 (16)O1—C17—H17C109.5
C7—C6—C1106.67 (17)H17A—C17—H17C109.5
C6—C7—H7A109.5H17B—C17—H17C109.5
C6—C7—H7B109.5O3—C18—H18A109.5
H7A—C7—H7B109.5O3—C18—H18B109.5
C6—C7—H7C109.5H18A—C18—H18B109.5
H7A—C7—H7C109.5O3—C18—H18C109.5
H7B—C7—H7C109.5H18A—C18—H18C109.5
C6—C8—H8A109.5H18B—C18—H18C109.5
C6—C8—H8B109.5
C2—N2—C1—N17.0 (2)C3—C4—C5—O34.7 (2)
C2—N2—C1—C6137.32 (17)N2—C1—C6—C856.5 (2)
C10—N1—C1—N2135.36 (16)N1—C1—C6—C874.2 (2)
C4—N1—C1—N220.5 (2)N2—C1—C6—C9178.85 (15)
C10—N1—C1—C696.41 (19)N1—C1—C6—C948.2 (2)
C4—N1—C1—C6107.72 (17)N2—C1—C6—C764.0 (2)
C1—N2—C2—O1177.38 (15)N1—C1—C6—C7165.38 (17)
C1—N2—C2—C33.0 (3)C4—N1—C10—O4157.06 (17)
C17—O1—C2—N24.5 (2)C1—N1—C10—O41.6 (3)
C17—O1—C2—C3175.86 (16)C4—N1—C10—C1126.1 (2)
N2—C2—C3—C426.2 (3)C1—N1—C10—C11178.50 (15)
O1—C2—C3—C4153.49 (14)O4—C10—C11—C16122.3 (2)
C10—N1—C4—C3106.96 (18)N1—C10—C11—C1654.7 (2)
C1—N1—C4—C348.13 (19)O4—C10—C11—C1250.4 (3)
C10—N1—C4—C5125.12 (17)N1—C10—C11—C12132.65 (18)
C1—N1—C4—C579.79 (19)C16—C11—C12—C131.0 (3)
C2—C3—C4—N148.18 (19)C10—C11—C12—C13173.76 (18)
C2—C3—C4—C577.44 (19)C11—C12—C13—C141.4 (3)
C18—O3—C5—O21.5 (3)C12—C13—C14—C151.0 (3)
C18—O3—C5—C4179.82 (17)C13—C14—C15—C160.1 (3)
N1—C4—C5—O261.5 (2)C12—C11—C16—C150.0 (3)
C3—C4—C5—O2174.07 (19)C10—C11—C16—C15172.60 (18)
N1—C4—C5—O3119.79 (17)C14—C15—C16—C110.4 (3)

Experimental details

Crystal data
Chemical formulaC18H24N2O4
Mr332.39
Crystal system, space groupMonoclinic, P21
Temperature (K)120
a, b, c (Å)10.283 (3), 8.124 (2), 11.757 (4)
β (°) 113.673 (11)
V3)899.5 (5)
Z2
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.45 × 0.25 × 0.10
Data collection
DiffractometerKappaCCD (with Oxford Cryostream)
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
8506, 2780, 2368
Rint0.025
(sin θ/λ)max1)0.703
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.039, 0.088, 1.03
No. of reflections2780
No. of parameters223
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.19, 0.18

Computer programs: COLLECT (Nonius, 2000), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997), SHELXL97.

Selected geometric parameters (Å, º) top
N1—C101.375 (2)N2—C21.262 (2)
N1—C41.471 (2)N2—C11.453 (2)
N1—C11.497 (2)
C2—N2—C1—N17.0 (2)N2—C2—C3—C426.2 (3)
C4—N1—C1—N220.5 (2)C1—N1—C4—C348.13 (19)
C1—N2—C2—C33.0 (3)C2—C3—C4—N148.18 (19)
C17—O1—C2—N24.5 (2)
 

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