organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoIUCrDATA
ISSN: 2414-3146

Methyl 3,3,6,6-tetra­methyl-1,8-dioxo-4,5,7,9-tetra­hydro-2H-xanthene-9-carboxyl­ate

aJohannes Gutenberg University Mainz, Department of Chemistry, Duesbergweg 10-14, 55099 Mainz, Germany
*Correspondence e-mail: detert@uni-mainz.de

Edited by J. F. Gallagher, Dublin City University, Ireland (Received 27 May 2020; accepted 23 July 2020; online 28 July 2020)

The title mol­ecule, C19H24O5, is built by annulation of a half-chair cyclo­hexenone and a twist-cyclo­hexenone to a flat 4-H-pyrane boat. In the crystal, mol­ecules are connected via van der Waals inter­actions and C—H⋯O hydrogen bonds.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

The title compound was obtained as a side product during the formation of methyl meth­oxy(2,6-dioxo-4,4-di­methyl­cyclo­hex­yl)acetate according to the procedure of Grosz & Freiberg (1966[Gross, H. & Freiberg, J. (1966). Chem. Ber. 99, 3260-3267.]). A similar product (1,2,3,4,5,6,7,8-octa­hydro-3,3,6,6-tetra­methyl-1,8-dioxo-9-xanthenyl acetic acid) was obtained by Gustafsson (1948[Gustafsson, C. (1948). Suomen Kemistilehti B, 21, 3-5.]) in the condensation of dimedone and glyoxalic acid. The free acid is an isomer of the title compound with a methyl­ene group connecting the heterocyclic unit and carb­oxy­lic acid group. A short route to these compounds is the uncatalysed tandem aldol condensation/elimination/Michael addition/condensation, as discovered by Rohr & Mahrwald (2009[Rohr, K. & Mahrwald, R. (2009). Bioorg. Med. Chem. Lett. 19, 3949-3951.]).

The mol­ecule is composed of two di­methyl­cyclo­hexenone units annulated to a central 4H-pyrane (Fig. 1[link]). While the conformation of the latter is a flat boat, one cyclo­hexenone (C2–C7) forms a half-chair and the other (C9–C14) has a twist form. The pyrane boat promotes a folded shape of the mol­ecule, the angle between the mean planes through atoms C1–C3/C6/C7/O8 and O8/C9/C10/C13//C14 being 22.42 (11)°, with maximum deviations from the mean planes at O8 [−0.1046 (18) Å] and C1 [0.051 (3) Å]. The torsion angle of the ester group (O17—C15—C1—C2) is 66.4 (3)°.

[Figure 1]
Figure 1
Perspective view of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Four mol­ecules occupy the monoclinic unit cell, the packing in the cell being dominated by van der Waals inter­actions and hydrogen-bonding inter­actions (Table 1[link] and Fig. 2[link]). The C—H⋯O hydrogen bonds (Steiner, 1996[Steiner, T. (1996). Crystallogr. Rev. 6, 1-51.]) C18—H18A⋯O17 and C18—H18A⋯O19 form a hydrogen-bonded dimer while the C6—H6B⋯O24 inter­action connects two mol­ecules related by the c-glide plane.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C6—H6B⋯O24i 0.99 2.50 3.324 (4) 140
C18—H18A⋯O17ii 0.98 2.53 3.451 (5) 156
C18—H18A⋯O19ii 0.98 2.41 3.093 (4) 126
Symmetry codes: (i) [x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]; (ii) -x+2, -y+1, -z+1.
[Figure 2]
Figure 2
Partial packing diagram of the title compound with a view along the b axis. Most of the hydrogen atoms omitted for clarity. Hydrogen bonds are depicted with dashed lines.

Synthesis and crystallization

Dimedone (7.01 g, 0.05 mol, 1 eq.) and tri­ethyl­amine (5.05 g, 50 mmol, 6.9 ml, 1 eq.) were dissolved in di­chloro­methane (25 ml) in a 250 ml flask under nitro­gen. Methyl chloro­meth­oxy­acetate (5.9 ml, 6.49 g, 0.525 mol, 1.05 eq.) was added dropwise to the ice-cooled mixture under stirring and the stirring was continued for 75 min at room temperature and a further 3 h under reflux conditions. The solvent was evaporated, methyl tert-butyl ether was added to the suspension and triethyl ammonium chloride was removed via filtration. The etheral layer was washed with aqueous sodium carbonate and brine, and dried over sodium sulfate. Evaporation of the solvent and chromatography (silica gel, petroleum ether/ethyl acetate = 3/1, Rf = 3:1) yielded 0.83 g (2.5 mmol, 5%) of the title compound as colourless crystals with m.p. = 474–478 K. The main product yield was 83%. Crystals of the title compound were obtained from a solution in ethyl acetate. IR: 2959, 2875, 1728, 1663, 1368, 1193, 995. 1H NMR (300 MHz, CDCl3) δ/p.p.m.: 4.47–4.46 (s, 1H), 3.68 (s, 3H), 2.43 (2*d, 2*2 gem H, J = 18 Hz), 4H), 2.27 (2*d, 2*2 gem H, J = 18 Hz), 1.11 (s, 12H).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula C19H24O5
Mr 332.38
Crystal system, space group Monoclinic, P21/c
Temperature (K) 120
a, b, c (Å) 13.1494 (10), 9.6899 (6), 14.8185 (13)
β (°) 113.295 (6)
V3) 1734.2 (2)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.09
Crystal size (mm) 0.22 × 0.11 × 0.06
 
Data collection
Diffractometer Stoe IPDS 2T
No. of measured, independent and observed [I > 2σ(I)] reflections 8583, 4123, 2784
Rint 0.036
(sin θ/λ)max−1) 0.659
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.072, 0.185, 1.05
No. of reflections 4123
No. of parameters 222
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.24, −0.30
Computer programs: X-AREA WinXpose, X-AREA Recipe and X-AREA Integrate (Stoe & Cie, 2019[Stoe & Cie (2019). X-RED and X-AREA. Stoe & Cie, Darmstadt, Germany.]), SIR2004 (Burla et al., 2005[Burla, M. C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G. L., De Caro, L., Giacovazzo, C., Polidori, G. & Spagna, R. (2005). J. Appl. Cryst. 38, 381-388.]), SHELXL2018/3 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]) and PLATON (Spek, 2020[Spek, A. L. (2020). Acta Cryst. E76, 1-11.]).

Structural data


Computing details top

Data collection: X-AREA WinXpose (Stoe & Cie, 2019); cell refinement: X-AREA Recipe (Stoe & Cie, 2019); data reduction: X-AREA Integrate (Stoe & Cie, 2019); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2020).

Methyl 3,3,6,6-tetramethyl-1,8-dioxo-4,5,7,9-tetrahydro-2H-xanthene-9-carboxylate top
Crystal data top
C19H24O5F(000) = 712
Mr = 332.38Dx = 1.273 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 13.1494 (10) ÅCell parameters from 9146 reflections
b = 9.6899 (6) Åθ = 2.6–28.2°
c = 14.8185 (13) ŵ = 0.09 mm1
β = 113.295 (6)°T = 120 K
V = 1734.2 (2) Å3Plate, colourless
Z = 40.22 × 0.11 × 0.06 mm
Data collection top
STOE IPDS 2T
diffractometer
2784 reflections with I > 2σ(I)
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focusRint = 0.036
Detector resolution: 6.67 pixels mm-1θmax = 28.0°, θmin = 2.6°
rotation method, ω scansh = 1617
8583 measured reflectionsk = 1212
4123 independent reflectionsl = 1919
Refinement top
Refinement on F2Primary atom site location: dual
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.072H-atom parameters constrained
wR(F2) = 0.185 w = 1/[σ2(Fo2) + (0.0577P)2 + 2.4014P]
where P = (Fo2 + 2Fc2)/3
S = 1.05(Δ/σ)max = 0.002
4123 reflectionsΔρmax = 0.24 e Å3
222 parametersΔρmin = 0.30 e Å3
0 restraints
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Hydrogen atoms attached to carbons were placed at calculated positions and were refined in the riding-model approximation with C–H = 0.95 Å, and with Uiso(H) = 1.2 Ueq(C).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.6910 (2)0.3522 (3)0.3759 (2)0.0290 (5)
H10.7155260.3376440.3207670.035*
C20.7343 (2)0.2359 (3)0.4490 (2)0.0284 (5)
C30.8403 (2)0.1694 (3)0.4650 (2)0.0292 (5)
C40.8801 (2)0.0564 (3)0.5415 (2)0.0327 (6)
H4A0.9621000.0565450.5708060.039*
H4B0.8556490.0338350.5086750.039*
C50.8385 (2)0.0705 (3)0.6237 (2)0.0302 (6)
C60.7113 (2)0.0808 (3)0.5759 (2)0.0313 (6)
H6A0.6799510.0100950.5482210.038*
H6B0.6831070.1053460.6266320.038*
C70.67398 (19)0.1865 (3)0.49633 (19)0.0270 (5)
O80.56625 (14)0.22547 (18)0.47408 (13)0.0293 (4)
C90.5126 (2)0.2955 (3)0.38683 (19)0.0283 (5)
C100.3910 (2)0.3002 (3)0.3590 (2)0.0301 (6)
H10A0.3759490.3132860.4188290.036*
H10B0.3580020.2110940.3288960.036*
C110.3362 (2)0.4177 (3)0.2862 (2)0.0312 (6)
C120.3794 (2)0.4120 (3)0.2043 (2)0.0329 (6)
H12A0.3548230.3247150.1672850.040*
H12B0.3470030.4892670.1580800.040*
C130.5040 (2)0.4207 (3)0.2430 (2)0.0302 (5)
C140.5668 (2)0.3511 (3)0.33598 (19)0.0276 (5)
C150.7354 (2)0.4908 (3)0.4252 (2)0.0307 (6)
O160.68175 (18)0.5800 (2)0.4402 (2)0.0579 (7)
O170.84313 (17)0.5003 (2)0.4521 (2)0.0606 (8)
C180.8958 (3)0.6248 (3)0.5039 (3)0.0611 (11)
H18A0.9762720.6166540.5252730.092*
H18B0.8775560.6372930.5613970.092*
H18C0.8692760.7044000.4600440.092*
O190.89116 (15)0.19842 (19)0.41368 (14)0.0334 (4)
C200.8901 (2)0.1983 (3)0.6859 (2)0.0369 (6)
H20A0.9710000.1906560.7126770.055*
H20B0.8652830.2049280.7400140.055*
H20C0.8670420.2811330.6448300.055*
C210.8723 (2)0.0569 (3)0.6899 (2)0.0407 (7)
H21A0.8412830.1396990.6507050.061*
H21B0.8441600.0486350.7417790.061*
H21C0.9532730.0639270.7196170.061*
C220.3647 (2)0.5576 (3)0.3387 (2)0.0386 (7)
H22A0.3324180.6318530.2909530.058*
H22B0.4453060.5686870.3691900.058*
H22C0.3345740.5617230.3894700.058*
C230.2108 (2)0.3990 (3)0.2434 (2)0.0386 (7)
H23A0.1757030.4757360.1988430.058*
H23B0.1846110.3976020.2968370.058*
H23C0.1914550.3118060.2071270.058*
O240.55164 (16)0.4811 (2)0.19806 (15)0.0394 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0238 (11)0.0255 (12)0.0370 (14)0.0006 (10)0.0111 (10)0.0008 (10)
C20.0257 (12)0.0230 (12)0.0356 (14)0.0012 (10)0.0110 (11)0.0004 (10)
C30.0251 (12)0.0255 (12)0.0373 (15)0.0023 (10)0.0125 (11)0.0049 (11)
C40.0301 (13)0.0271 (13)0.0409 (16)0.0045 (11)0.0142 (12)0.0013 (11)
C50.0253 (12)0.0290 (13)0.0340 (14)0.0027 (10)0.0095 (11)0.0048 (11)
C60.0294 (12)0.0268 (12)0.0375 (15)0.0010 (11)0.0131 (11)0.0041 (11)
C70.0209 (11)0.0234 (11)0.0349 (14)0.0004 (9)0.0091 (10)0.0030 (10)
O80.0231 (8)0.0295 (9)0.0348 (10)0.0014 (7)0.0109 (7)0.0041 (8)
C90.0268 (12)0.0237 (12)0.0326 (14)0.0025 (10)0.0100 (10)0.0026 (10)
C100.0240 (12)0.0266 (13)0.0385 (15)0.0018 (10)0.0110 (11)0.0034 (11)
C110.0251 (12)0.0267 (13)0.0402 (15)0.0024 (10)0.0113 (11)0.0050 (11)
C120.0279 (12)0.0315 (13)0.0380 (15)0.0011 (11)0.0115 (11)0.0021 (11)
C130.0297 (12)0.0256 (12)0.0351 (14)0.0012 (10)0.0125 (11)0.0017 (11)
C140.0244 (11)0.0229 (12)0.0344 (14)0.0005 (10)0.0103 (10)0.0008 (10)
C150.0262 (12)0.0258 (12)0.0396 (15)0.0022 (10)0.0124 (11)0.0033 (11)
O160.0392 (12)0.0427 (13)0.094 (2)0.0050 (10)0.0282 (13)0.0255 (13)
O170.0286 (11)0.0317 (11)0.116 (2)0.0079 (9)0.0229 (13)0.0240 (13)
C180.0410 (17)0.0309 (16)0.104 (3)0.0120 (14)0.0204 (19)0.0201 (18)
O190.0305 (9)0.0317 (10)0.0425 (11)0.0013 (8)0.0193 (9)0.0026 (8)
C200.0311 (13)0.0402 (16)0.0355 (15)0.0013 (12)0.0089 (12)0.0025 (12)
C210.0368 (15)0.0381 (16)0.0460 (18)0.0077 (13)0.0151 (13)0.0103 (13)
C220.0377 (14)0.0295 (14)0.0512 (18)0.0048 (12)0.0204 (14)0.0010 (13)
C230.0289 (13)0.0376 (15)0.0461 (17)0.0024 (12)0.0112 (12)0.0106 (13)
O240.0367 (10)0.0391 (11)0.0470 (12)0.0054 (9)0.0214 (10)0.0129 (9)
Geometric parameters (Å, º) top
C1—C141.501 (3)C11—C121.532 (4)
C1—C21.510 (4)C11—C221.534 (4)
C1—C151.530 (4)C12—C131.508 (3)
C1—H11.0000C12—H12A0.9900
C2—C71.337 (3)C12—H12B0.9900
C2—C31.468 (3)C13—O241.229 (3)
C3—O191.228 (3)C13—C141.461 (4)
C3—C41.513 (4)C15—O161.191 (3)
C4—C51.526 (4)C15—O171.314 (3)
C4—H4A0.9900O17—C181.450 (4)
C4—H4B0.9900C18—H18A0.9800
C5—C211.529 (4)C18—H18B0.9800
C5—C201.533 (4)C18—H18C0.9800
C5—C61.541 (3)C20—H20A0.9800
C6—C71.490 (4)C20—H20B0.9800
C6—H6A0.9900C20—H20C0.9800
C6—H6B0.9900C21—H21A0.9800
C7—O81.374 (3)C21—H21B0.9800
O8—C91.381 (3)C21—H21C0.9800
C9—C141.338 (3)C22—H22A0.9800
C9—C101.486 (3)C22—H22B0.9800
C10—C111.538 (4)C22—H22C0.9800
C10—H10A0.9900C23—H23A0.9800
C10—H10B0.9900C23—H23B0.9800
C11—C231.526 (3)C23—H23C0.9800
C14—C1—C2108.7 (2)C22—C11—C10110.2 (2)
C14—C1—C15110.2 (2)C13—C12—C11112.6 (2)
C2—C1—C15110.4 (2)C13—C12—H12A109.1
C14—C1—H1109.2C11—C12—H12A109.1
C2—C1—H1109.2C13—C12—H12B109.1
C15—C1—H1109.2C11—C12—H12B109.1
C7—C2—C3118.7 (2)H12A—C12—H12B107.8
C7—C2—C1120.7 (2)O24—C13—C14120.7 (2)
C3—C2—C1120.5 (2)O24—C13—C12122.0 (2)
O19—C3—C2121.0 (2)C14—C13—C12117.2 (2)
O19—C3—C4121.2 (2)C9—C14—C13119.2 (2)
C2—C3—C4117.7 (2)C9—C14—C1121.3 (2)
C3—C4—C5114.0 (2)C13—C14—C1119.4 (2)
C3—C4—H4A108.8O16—C15—O17122.7 (3)
C5—C4—H4A108.8O16—C15—C1125.7 (2)
C3—C4—H4B108.8O17—C15—C1111.6 (2)
C5—C4—H4B108.8C15—O17—C18116.8 (2)
H4A—C4—H4B107.7O17—C18—H18A109.5
C4—C5—C21109.6 (2)O17—C18—H18B109.5
C4—C5—C20109.8 (2)H18A—C18—H18B109.5
C21—C5—C20108.6 (2)O17—C18—H18C109.5
C4—C5—C6107.8 (2)H18A—C18—H18C109.5
C21—C5—C6109.6 (2)H18B—C18—H18C109.5
C20—C5—C6111.5 (2)C5—C20—H20A109.5
C7—C6—C5111.5 (2)C5—C20—H20B109.5
C7—C6—H6A109.3H20A—C20—H20B109.5
C5—C6—H6A109.3C5—C20—H20C109.5
C7—C6—H6B109.3H20A—C20—H20C109.5
C5—C6—H6B109.3H20B—C20—H20C109.5
H6A—C6—H6B108.0C5—C21—H21A109.5
C2—C7—O8123.0 (2)C5—C21—H21B109.5
C2—C7—C6125.6 (2)H21A—C21—H21B109.5
O8—C7—C6111.4 (2)C5—C21—H21C109.5
C7—O8—C9117.1 (2)H21A—C21—H21C109.5
C14—C9—O8122.5 (2)H21B—C21—H21C109.5
C14—C9—C10125.8 (2)C11—C22—H22A109.5
O8—C9—C10111.7 (2)C11—C22—H22B109.5
C9—C10—C11111.8 (2)H22A—C22—H22B109.5
C9—C10—H10A109.2C11—C22—H22C109.5
C11—C10—H10A109.2H22A—C22—H22C109.5
C9—C10—H10B109.2H22B—C22—H22C109.5
C11—C10—H10B109.2C11—C23—H23A109.5
H10A—C10—H10B107.9C11—C23—H23B109.5
C23—C11—C12110.2 (2)H23A—C23—H23B109.5
C23—C11—C22108.8 (2)C11—C23—H23C109.5
C12—C11—C22109.9 (2)H23A—C23—H23C109.5
C23—C11—C10109.5 (2)H23B—C23—H23C109.5
C12—C11—C10108.1 (2)
C14—C1—C2—C725.2 (3)O8—C9—C10—C11159.3 (2)
C15—C1—C2—C795.7 (3)C9—C10—C11—C23167.9 (2)
C14—C1—C2—C3151.0 (2)C9—C10—C11—C1247.7 (3)
C15—C1—C2—C388.1 (3)C9—C10—C11—C2272.5 (3)
C7—C2—C3—O19170.0 (2)C23—C11—C12—C13176.3 (2)
C1—C2—C3—O196.3 (4)C22—C11—C12—C1363.7 (3)
C7—C2—C3—C45.4 (4)C10—C11—C12—C1356.7 (3)
C1—C2—C3—C4178.2 (2)C11—C12—C13—O24144.6 (3)
O19—C3—C4—C5156.8 (2)C11—C12—C13—C1436.9 (3)
C2—C3—C4—C527.7 (3)O8—C9—C14—C13178.5 (2)
C3—C4—C5—C21173.5 (2)C10—C9—C14—C131.7 (4)
C3—C4—C5—C2067.3 (3)O8—C9—C14—C15.9 (4)
C3—C4—C5—C654.3 (3)C10—C9—C14—C1173.9 (2)
C4—C5—C6—C749.8 (3)O24—C13—C14—C9174.9 (3)
C21—C5—C6—C7168.9 (2)C12—C13—C14—C96.5 (4)
C20—C5—C6—C770.8 (3)O24—C13—C14—C10.8 (4)
C3—C2—C7—O8168.6 (2)C12—C13—C14—C1177.8 (2)
C1—C2—C7—O87.7 (4)C2—C1—C14—C924.4 (3)
C3—C2—C7—C69.2 (4)C15—C1—C14—C996.7 (3)
C1—C2—C7—C6174.5 (2)C2—C1—C14—C13160.0 (2)
C5—C6—C7—C220.1 (4)C15—C1—C14—C1378.9 (3)
C5—C6—C7—O8161.9 (2)C14—C1—C15—O167.8 (4)
C2—C7—O8—C913.7 (3)C2—C1—C15—O16112.2 (3)
C6—C7—O8—C9164.4 (2)C14—C1—C15—O17173.5 (2)
C7—O8—C9—C1414.7 (4)C2—C1—C15—O1766.4 (3)
C7—O8—C9—C10165.5 (2)O16—C15—O17—C181.4 (5)
C14—C9—C10—C1120.5 (4)C1—C15—O17—C18177.2 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C6—H6B···O24i0.992.503.324 (4)140
C18—H18A···O17ii0.982.533.451 (5)156
C18—H18A···O19ii0.982.413.093 (4)126
Symmetry codes: (i) x, y+1/2, z+1/2; (ii) x+2, y+1, z+1.
 

References

First citationBurla, M. C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G. L., De Caro, L., Giacovazzo, C., Polidori, G. & Spagna, R. (2005). J. Appl. Cryst. 38, 381–388.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationGross, H. & Freiberg, J. (1966). Chem. Ber. 99, 3260–3267.  CAS Google Scholar
First citationGustafsson, C. (1948). Suomen Kemistilehti B, 21, 3–5.  Google Scholar
First citationRohr, K. & Mahrwald, R. (2009). Bioorg. Med. Chem. Lett. 19, 3949–3951.  Web of Science CrossRef PubMed CAS Google Scholar
First citationSheldrick, G. M. (2015). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSpek, A. L. (2020). Acta Cryst. E76, 1–11.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSteiner, T. (1996). Crystallogr. Rev. 6, 1–51.  CrossRef CAS Google Scholar
First citationStoe & Cie (2019). X-RED and X-AREA. Stoe & Cie, Darmstadt, Germany.  Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoIUCrDATA
ISSN: 2414-3146
Follow IUCr Journals
Sign up for e-alerts
Follow IUCr on Twitter
Follow us on facebook
Sign up for RSS feeds