One of the products obtained from the fruit of the indigenous Australian tree
Melicope ellyrana has been confirmed as the flavonoid pachypodol (4,5′-dihydroxy-3,3′,7-trimethoxyflavone), C
18H
16O
7. This compound is similar to a number of the flavonones from the same species with the exception of the reduced side chain. The usual intramolecular hydrogen bonding between the hydroxy and the adjacent carbonyl or methoxy substituent groups is found, together with intermolecular hydrogen bonding between one of these hydroxy groups and a methoxy O atom [O
O 2.875 (4) Å], giving an infinite chain.
Supporting information
CCDC reference: 175372
Key indicators
- Single-crystal X-ray study
- T = 293 K
- Mean (C-C) = 0.005 Å
- R factor = 0.045
- wR factor = 0.155
- Data-to-parameter ratio = 12.0
checkCIF results
No syntax errors found
ADDSYM reports no extra symmetry
The title compound was obtained as one of the 23 fractions from the n-hexane
extract of the fresh fruit of Melicope ellyrana (Smith et al.,
2001a).
The H atoms of both hydroxyl groups were located from a difference map and their
positional parameters only were refined while the remainder were included at
calculated positions and allowed to ride with the attached atom.
Data collection: MSC/AFC Diffractometer Control Software
(Molecular Structure Corporation, 1999a); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN for Windows (Molecular Structure Corporation, 1999b); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON for Windows (Spek, 1999); software used to prepare material for publication: TEXSAN for Windows.
4,5'-dihydroxy-3,3',7-trimethoxyflavone
top
Crystal data top
C18H16O7 | Z = 2 |
Mr = 344.31 | F(000) = 360 |
Triclinic, P1 | Dx = 1.442 Mg m−3 |
a = 9.399 (6) Å | Mo Kα radiation, λ = 0.71069 Å |
b = 11.836 (9) Å | Cell parameters from 25 reflections |
c = 8.041 (3) Å | θ = 11.0–19.5° |
α = 97.64 (5)° | µ = 0.11 mm−1 |
β = 111.08 (3)° | T = 293 K |
γ = 71.83 (7)° | Prismatic, yellow |
V = 792.8 (8) Å3 | 0.60 × 0.20 × 0.20 mm |
Data collection top
Rigaku AFC-7R diffractometer | Rint = 0.073 |
Radiation source: Rigaku rotating anode | θmax = 25.1°, θmin = 2.6° |
Graphite monochromator | h = 0→11 |
ω–2θ scans | k = −13→14 |
2983 measured reflections | l = −9→8 |
2798 independent reflections | 3 standard reflections every 150 reflections |
1383 reflections with I > 2σ(I) | intensity decay: 0.8% |
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)] = 0.045 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.155 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.00 | w = 1/[σ2(Fo2) + (0.0773P)2 + 0.0882P] where P = (Fo2 + 2Fc2)/3 |
2798 reflections | (Δ/σ)max < 0.001 |
233 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.29 e Å−3 |
Crystal data top
C18H16O7 | γ = 71.83 (7)° |
Mr = 344.31 | V = 792.8 (8) Å3 |
Triclinic, P1 | Z = 2 |
a = 9.399 (6) Å | Mo Kα radiation |
b = 11.836 (9) Å | µ = 0.11 mm−1 |
c = 8.041 (3) Å | T = 293 K |
α = 97.64 (5)° | 0.60 × 0.20 × 0.20 mm |
β = 111.08 (3)° | |
Data collection top
Rigaku AFC-7R diffractometer | Rint = 0.073 |
2983 measured reflections | 3 standard reflections every 150 reflections |
2798 independent reflections | intensity decay: 0.8% |
1383 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.045 | 0 restraints |
wR(F2) = 0.155 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.00 | Δρmax = 0.20 e Å−3 |
2798 reflections | Δρmin = −0.29 e Å−3 |
233 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 | x | y | z | Uiso*/Ueq | |
O1 | 0.5549 (2) | 0.67398 (16) | 0.4730 (3) | 0.0416 (6) | |
O2 | 0.7168 (3) | 0.30782 (19) | 0.1726 (3) | 0.0572 (7) | |
O3 | 0.1697 (2) | 0.87229 (17) | 0.4575 (3) | 0.0447 (6) | |
O4 | 0.7394 (3) | 1.0726 (2) | 1.0165 (3) | 0.0602 (7) | |
O5 | 0.4334 (2) | 1.16198 (17) | 0.8146 (3) | 0.0500 (6) | |
O6 | 0.0885 (3) | 0.6939 (2) | 0.2185 (3) | 0.0642 (7) | |
O7 | 0.1743 (3) | 0.4917 (2) | 0.0539 (3) | 0.0666 (8) | |
C1 | 0.4398 (3) | 0.7707 (2) | 0.5028 (4) | 0.0382 (7) | |
C2 | 0.2840 (3) | 0.7803 (2) | 0.4158 (4) | 0.0384 (7) | |
C3 | 0.2329 (4) | 0.6885 (3) | 0.2918 (4) | 0.0426 (8) | |
C4 | 0.3578 (3) | 0.5905 (2) | 0.2616 (4) | 0.0390 (7) | |
C5 | 0.3259 (4) | 0.4943 (3) | 0.1424 (4) | 0.0460 (8) | |
C6 | 0.4496 (4) | 0.4029 (3) | 0.1164 (4) | 0.0484 (8) | |
C7 | 0.6058 (4) | 0.4030 (2) | 0.2094 (4) | 0.0433 (8) | |
C8 | 0.6428 (4) | 0.4942 (3) | 0.3299 (4) | 0.0426 (8) | |
C9 | 0.5163 (3) | 0.5859 (2) | 0.3514 (4) | 0.0372 (7) | |
C10 | 0.5142 (3) | 0.8505 (2) | 0.6393 (4) | 0.0365 (7) | |
C11 | 0.6709 (4) | 0.8100 (3) | 0.7484 (4) | 0.0432 (8) | |
C12 | 0.7448 (4) | 0.8843 (3) | 0.8746 (4) | 0.0457 (8) | |
C13 | 0.6618 (3) | 1.0015 (3) | 0.8936 (4) | 0.0413 (8) | |
C14 | 0.5040 (3) | 1.0443 (2) | 0.7858 (4) | 0.0382 (7) | |
C15 | 0.4307 (3) | 0.9697 (3) | 0.6611 (4) | 0.0415 (8) | |
C16 | 0.2678 (4) | 1.2085 (3) | 0.7215 (5) | 0.0558 (9) | |
C17 | 0.0697 (4) | 0.9524 (3) | 0.3142 (5) | 0.0561 (9) | |
C18 | 0.8813 (5) | 0.2993 (3) | 0.2640 (6) | 0.0685 (11) | |
H1 | 0.672 (4) | 1.135 (3) | 1.015 (5) | 0.058* | |
H2 | 0.4282 | 0.3398 | 0.0342 | 0.057* | |
H3 | 0.7287 | 0.7294 | 0.7367 | 0.052* | |
H4 | 0.8528 | 0.8545 | 0.9486 | 0.054* | |
H5 | 0.3221 | 0.9994 | 0.5897 | 0.050* | |
H6 | 0.2289 | 1.2846 | 0.7701 | 0.066* | |
H9 | −0.0047 | 1.0138 | 0.3534 | 0.067* | |
H10 | 0.1336 | 0.9858 | 0.2785 | 0.067* | |
H11 | 0.0149 | 0.9099 | 0.2162 | 0.067* | |
H12 | 0.9042 | 0.2967 | 0.3882 | 0.081* | |
H13 | 0.9446 | 0.2288 | 0.2246 | 0.081* | |
H14 | 0.9037 | 0.3665 | 0.2377 | 0.081* | |
H15 | 0.117 (4) | 0.559 (3) | 0.095 (5) | 0.061* | |
H16 | 0.7498 | 0.4945 | 0.3940 | 0.051* | |
H7 | 0.2508 | 1.2160 | 0.5986 | 0.066* | |
H8 | 0.2125 | 1.1564 | 0.7315 | 0.066* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0384 (12) | 0.0310 (11) | 0.0449 (12) | −0.0064 (9) | 0.0090 (10) | −0.0107 (9) |
O2 | 0.0589 (15) | 0.0388 (13) | 0.0642 (16) | −0.0031 (11) | 0.0241 (13) | −0.0135 (11) |
O3 | 0.0400 (12) | 0.0361 (12) | 0.0487 (13) | −0.0034 (10) | 0.0129 (10) | −0.0058 (10) |
O4 | 0.0475 (14) | 0.0438 (14) | 0.0659 (16) | −0.0088 (11) | 0.0042 (12) | −0.0234 (13) |
O5 | 0.0404 (13) | 0.0330 (12) | 0.0616 (15) | −0.0051 (10) | 0.0095 (11) | −0.0132 (10) |
O6 | 0.0426 (14) | 0.0515 (14) | 0.0832 (18) | −0.0138 (11) | 0.0109 (13) | −0.0205 (13) |
O7 | 0.0529 (16) | 0.0486 (15) | 0.0804 (19) | −0.0178 (12) | 0.0081 (14) | −0.0246 (13) |
C1 | 0.0423 (19) | 0.0264 (15) | 0.0414 (18) | −0.0059 (14) | 0.0138 (15) | −0.0037 (13) |
C2 | 0.0386 (18) | 0.0284 (16) | 0.0444 (19) | −0.0049 (13) | 0.0150 (15) | −0.0033 (13) |
C3 | 0.0376 (19) | 0.0375 (17) | 0.048 (2) | −0.0121 (14) | 0.0094 (15) | −0.0032 (14) |
C4 | 0.0427 (18) | 0.0311 (16) | 0.0383 (17) | −0.0100 (14) | 0.0096 (14) | −0.0025 (13) |
C5 | 0.049 (2) | 0.0374 (18) | 0.0465 (19) | −0.0162 (15) | 0.0098 (15) | −0.0088 (15) |
C6 | 0.062 (2) | 0.0343 (17) | 0.0452 (19) | −0.0148 (16) | 0.0167 (17) | −0.0098 (14) |
C7 | 0.052 (2) | 0.0294 (16) | 0.0467 (19) | −0.0064 (14) | 0.0201 (16) | −0.0029 (14) |
C8 | 0.0458 (19) | 0.0326 (16) | 0.0445 (19) | −0.0076 (14) | 0.0147 (15) | −0.0052 (14) |
C9 | 0.0436 (18) | 0.0300 (16) | 0.0359 (17) | −0.0113 (14) | 0.0119 (14) | −0.0042 (13) |
C10 | 0.0379 (17) | 0.0329 (16) | 0.0358 (16) | −0.0094 (13) | 0.0109 (14) | −0.0023 (13) |
C11 | 0.0444 (19) | 0.0305 (16) | 0.0480 (19) | −0.0056 (14) | 0.0145 (15) | −0.0063 (14) |
C12 | 0.0367 (17) | 0.0429 (18) | 0.0446 (19) | −0.0060 (14) | 0.0058 (14) | −0.0065 (15) |
C13 | 0.0404 (18) | 0.0378 (18) | 0.0408 (18) | −0.0123 (14) | 0.0104 (15) | −0.0090 (14) |
C14 | 0.0434 (18) | 0.0259 (15) | 0.0431 (18) | −0.0069 (13) | 0.0179 (15) | −0.0087 (13) |
C15 | 0.0344 (17) | 0.0347 (17) | 0.0461 (19) | −0.0055 (14) | 0.0081 (14) | −0.0036 (14) |
C16 | 0.043 (2) | 0.0390 (19) | 0.071 (2) | −0.0038 (15) | 0.0109 (17) | −0.0051 (17) |
C17 | 0.051 (2) | 0.0409 (19) | 0.062 (2) | −0.0023 (16) | 0.0109 (17) | 0.0015 (17) |
C18 | 0.063 (3) | 0.050 (2) | 0.089 (3) | −0.0011 (18) | 0.037 (2) | −0.0074 (19) |
Geometric parameters (Å, º) top
O1—C9 | 1.372 (3) | C7—C8 | 1.393 (4) |
O1—C1 | 1.371 (3) | C8—C9 | 1.384 (4) |
O2—C7 | 1.358 (4) | C8—H16 | 0.95 |
O2—C18 | 1.431 (4) | C10—C11 | 1.382 (4) |
O3—C2 | 1.373 (3) | C10—C15 | 1.408 (4) |
O3—C17 | 1.437 (4) | C11—C12 | 1.386 (4) |
O4—C13 | 1.364 (4) | C11—H3 | 0.95 |
O4—H1 | 0.81 (3) | C12—C13 | 1.381 (4) |
O5—C14 | 1.372 (3) | C12—H4 | 0.95 |
O5—C16 | 1.422 (4) | C13—C14 | 1.390 (4) |
O6—C3 | 1.255 (4) | C14—C15 | 1.380 (4) |
O7—C5 | 1.353 (4) | C15—H5 | 0.95 |
O7—H15 | 0.91 (3) | C16—H6 | 0.95 |
C1—C2 | 1.352 (4) | C16—H7 | 0.96 |
C1—C10 | 1.472 (4) | C16—H8 | 0.95 |
C2—C3 | 1.448 (4) | C17—H9 | 0.95 |
C3—C4 | 1.436 (4) | C17—H10 | 0.95 |
C4—C9 | 1.389 (4) | C17—H11 | 0.95 |
C4—C5 | 1.422 (4) | C18—H12 | 0.95 |
C5—C6 | 1.377 (5) | C18—H13 | 0.95 |
C6—C7 | 1.388 (4) | C18—H14 | 0.95 |
C6—H2 | 0.95 | | |
| | | |
C9—O1—C1 | 121.4 (2) | C15—C10—C1 | 121.7 (3) |
C7—O2—C18 | 118.5 (3) | C10—C11—C12 | 121.4 (3) |
C2—O3—C17 | 114.3 (2) | C10—C11—H3 | 119 |
C13—O4—H1 | 105 (3) | C12—C11—H3 | 120 |
C14—O5—C16 | 117.8 (2) | C13—C12—C11 | 120.1 (3) |
C5—O7—H15 | 102 (2) | C13—C12—H4 | 120 |
C2—C1—O1 | 120.5 (2) | C11—C12—H4 | 120 |
C2—C1—C10 | 129.5 (3) | O4—C13—C12 | 118.5 (3) |
O1—C1—C10 | 109.9 (2) | O4—C13—C14 | 121.8 (3) |
C1—C2—O3 | 120.0 (3) | C12—C13—C14 | 119.7 (3) |
C1—C2—C3 | 121.6 (3) | O5—C14—C15 | 125.1 (3) |
O3—C2—C3 | 118.0 (3) | O5—C14—C13 | 114.9 (3) |
O6—C3—C4 | 122.5 (3) | C15—C14—C13 | 120.0 (3) |
O6—C3—C2 | 121.7 (3) | C14—C15—C10 | 120.9 (3) |
C4—C3—C2 | 115.8 (3) | C14—C15—H5 | 119 |
C9—C4—C5 | 117.3 (3) | C10—C15—H5 | 120 |
C9—C4—C3 | 120.5 (3) | O5—C16—H6 | 110 |
C5—C4—C3 | 122.2 (3) | O5—C16—H7 | 109 |
O7—C5—C6 | 119.5 (3) | H6—C16—H7 | 109 |
O7—C5—C4 | 120.4 (3) | O5—C16—H8 | 110 |
C6—C5—C4 | 120.1 (3) | H6—C16—H8 | 110 |
C5—C6—C7 | 120.1 (3) | H7—C16—H8 | 109 |
C5—C6—H2 | 120 | O3—C17—H9 | 109 |
C7—C6—H2 | 120 | O3—C17—H10 | 109 |
O2—C7—C6 | 114.5 (3) | H9—C17—H10 | 110 |
O2—C7—C8 | 123.7 (3) | O3—C17—H11 | 109 |
C6—C7—C8 | 121.8 (3) | H9—C17—H11 | 110 |
C9—C8—C7 | 116.8 (3) | H10—C17—H11 | 110 |
C9—C8—H16 | 121 | O2—C18—H12 | 110 |
C7—C8—H16 | 122 | O2—C18—H13 | 109 |
O1—C9—C8 | 116.1 (3) | H12—C18—H13 | 110 |
O1—C9—C4 | 120.1 (3) | O2—C18—H14 | 109 |
C8—C9—C4 | 123.8 (3) | H12—C18—H14 | 110 |
C11—C10—C15 | 117.9 (3) | H13—C18—H14 | 109 |
C11—C10—C1 | 120.3 (3) | | |
| | | |
C9—O1—C1—C2 | 1.7 (4) | C1—O1—C9—C8 | 178.5 (3) |
C9—O1—C1—C10 | 179.8 (2) | C1—O1—C9—C4 | −3.1 (4) |
O1—C1—C2—O3 | 174.5 (3) | C7—C8—C9—O1 | 178.9 (3) |
C10—C1—C2—O3 | −3.2 (5) | C7—C8—C9—C4 | 0.5 (5) |
O1—C1—C2—C3 | 1.4 (5) | C5—C4—C9—O1 | −177.7 (3) |
C10—C1—C2—C3 | −176.4 (3) | C3—C4—C9—O1 | 1.4 (4) |
C17—O3—C2—C1 | 116.6 (3) | C5—C4—C9—C8 | 0.6 (5) |
C17—O3—C2—C3 | −70.0 (4) | C3—C4—C9—C8 | 179.7 (3) |
C1—C2—C3—O6 | 175.9 (3) | C2—C1—C10—C11 | 161.4 (3) |
O3—C2—C3—O6 | 2.6 (5) | O1—C1—C10—C11 | −16.6 (4) |
C1—C2—C3—C4 | −2.8 (4) | C2—C1—C10—C15 | −19.9 (5) |
O3—C2—C3—C4 | −176.1 (3) | O1—C1—C10—C15 | 162.2 (3) |
O6—C3—C4—C9 | −177.3 (3) | C15—C10—C11—C12 | −0.6 (5) |
C2—C3—C4—C9 | 1.5 (4) | C1—C10—C11—C12 | 178.2 (3) |
O6—C3—C4—C5 | 1.8 (5) | C10—C11—C12—C13 | 0.0 (5) |
C2—C3—C4—C5 | −179.5 (3) | C11—C12—C13—O4 | −178.6 (3) |
C9—C4—C5—O7 | 178.4 (3) | C11—C12—C13—C14 | 0.1 (5) |
C3—C4—C5—O7 | −0.7 (5) | C16—O5—C14—C15 | 6.4 (4) |
C9—C4—C5—C6 | −1.6 (5) | C16—O5—C14—C13 | −173.9 (3) |
C3—C4—C5—C6 | 179.3 (3) | O4—C13—C14—O5 | −0.7 (4) |
O7—C5—C6—C7 | −178.5 (3) | C12—C13—C14—O5 | −179.5 (3) |
C4—C5—C6—C7 | 1.4 (5) | O4—C13—C14—C15 | 179.0 (3) |
C18—O2—C7—C6 | −179.1 (3) | C12—C13—C14—C15 | 0.3 (5) |
C18—O2—C7—C8 | 0.9 (5) | O5—C14—C15—C10 | 178.9 (3) |
C5—C6—C7—O2 | 179.7 (3) | C13—C14—C15—C10 | −0.9 (5) |
C5—C6—C7—C8 | −0.3 (5) | C11—C10—C15—C14 | 1.0 (5) |
O2—C7—C8—C9 | 179.3 (3) | C1—C10—C15—C14 | −177.8 (3) |
C6—C7—C8—C9 | −0.7 (5) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H1···O2i | 0.81 (4) | 2.33 (4) | 2.875 (4) | 125 (3) |
O4—H1···O5 | 0.81 (4) | 2.20 (4) | 2.688 (4) | 120 (3) |
O7—H15···O6 | 0.91 (4) | 1.76 (3) | 2.618 (4) | 156 (4) |
C6—H2···O5ii | 0.95 | 2.56 | 3.494 (5) | 167 |
C11—H3···O1 | 0.95 | 2.32 | 2.664 (4) | 100 |
C15—H5···O3 | 0.95 | 2.30 | 2.898 (4) | 121 |
C17—H9···O3iii | 0.95 | 2.53 | 3.433 (5) | 160 |
C17—H11···O6 | 0.95 | 2.43 | 3.020 (5) | 120 |
Symmetry codes: (i) x, y+1, z+1; (ii) x, y−1, z−1; (iii) −x, −y+2, −z+1. |
Experimental details
Crystal data |
Chemical formula | C18H16O7 |
Mr | 344.31 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 9.399 (6), 11.836 (9), 8.041 (3) |
α, β, γ (°) | 97.64 (5), 111.08 (3), 71.83 (7) |
V (Å3) | 792.8 (8) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.60 × 0.20 × 0.20 |
|
Data collection |
Diffractometer | Rigaku AFC-7R diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2983, 2798, 1383 |
Rint | 0.073 |
(sin θ/λ)max (Å−1) | 0.596 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.155, 1.00 |
No. of reflections | 2798 |
No. of parameters | 233 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.20, −0.29 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H1···O2i | 0.81 (4) | 2.33 (4) | 2.875 (4) | 125 (3) |
O4—H1···O5 | 0.81 (4) | 2.20 (4) | 2.688 (4) | 120 (3) |
O7—H15···O6 | 0.91 (4) | 1.76 (3) | 2.618 (4) | 156 (4) |
C6—H2···O5ii | 0.95 | 2.56 | 3.494 (5) | 167 |
C11—H3···O1 | 0.95 | 2.32 | 2.664 (4) | 100 |
C15—H5···O3 | 0.95 | 2.30 | 2.898 (4) | 121 |
C17—H9···O3iii | 0.95 | 2.53 | 3.433 (5) | 160 |
C17—H11···O6 | 0.95 | 2.43 | 3.020 (5) | 120 |
Symmetry codes: (i) x, y+1, z+1; (ii) x, y−1, z−1; (iii) −x, −y+2, −z+1. |
The hexane extract of the fruit of the indigenous Australian tree Melicope ellyrana (formerly Euodia ellyrana F. Meull) (Hartley, 1981) has yielded, among other products the flavonoids, pachypodol [4',5-dihydroxy-3,3',7-trimethoxyflavone, (I)], ternatin [4',5-dihydroxy-3,3',7,8-tetramethoxyflavone, (II)], 4',5-dihydroxy-3,3',8-trimethoxy-7-(3-methylbut-2-enyloxy)flavone, (III), and 3',5-dihydroxy-3,4'-dimethoxy-7-(3-methylbut-2-enyloxy)flavone, (IV). Both (III) and (IV) have provided examples of dimorphism [for (III), triclinic and monoclinic (Smith et al., 2001a) and (IV), both triclinic representing distinctly different conformational variants (Smith et al., 2001b)]. With (III), this was the first report of its isolation from Melicope species, although it had previously been isolated from Boronia coerulescens (Ashan et al., 1994), while other prenylated flavones similar to (III) and (IV) have been reported, from M. triphylla (Higa et al., 1987) and M. micrococca (Nasim, 1999). Pachypodol has also been isolated from other plant types, e.g. Larrea cuneifolia (Valesi et al., 1972) and L. tridenta (Chirikdjian, 1974) as well as Pachypodanthium confine (Annonaceae) (Cave et al., 1973), but not previously from Melicope species.
The structure has revealed the basic flavone core similar to other reported flavonoids, e.g. 5-hydroxy-3,4',7-trimethoxyflavone (Gajhede et al., 1989), and to the other flavonone components from the same species. The greatest similarity is with the structure of the dimorphic pair (IV) but with the 3-methylbut-2-enyl side chain at C7 reduced. The usual intramolecular C—H···O (methoxy) and C—H···O (ether) interaction is significant in maintaining close to coplanarity in the two ring systems [C11—H3···O1 2.664 (4) Å and C15—H5···O3 2.898 (4) Å; torsion angle C2—C1—C10—C11 161.3 (4)°]. There is an intramolecular hydrogen-bonding interaction involving the hydroxyl group at C5 and the adjacent ketone oxygen (at C3) [O7—H15···O6 2.618 (4) Å] and between the hydroxyl group at C13 and the adjacent methoxy oxygen (at C14) [O4—H1···O5 2.688 (4) Å]. A single intermolecular hydrogen-bonding interaction is found between the H atom on this hydroxyl group and a methoxy O atom of an adjacent neighbour [O4—H1···O2 2.875 (4) Å; symmetry code: x, 1 + y, 1 + z]. This completes a three-centered hydrogen-bonding association about H1 and together with a weak C6—H2···O5 contact [3.494 (5) Å; symmetry code: x, -1 + y, -1 + z] gives an infinite chain parallel to the `b' cell direction (Fig. 2). Unusual weak centrosymmetric cyclic hydrogen-bonding intermolecular associations between the oxygen and a methyl H atom of the methoxy substituent group at C2 link the primary chains peripherally [C17—H9···O3 3.433 (5) Å; symmetry code: -x, 2 - y, 1 - z].