organic compounds
6-[Bis(ethoxycarbonyl)methyl]-6-deoxy-1,2;3,4-di-O-isopropylidene-D-galactopyranose
aDepartamento de Química, Universidade Federal Rural de Pernambuco, 52171-900 Recife, PE, Brazil, bChemistry Department, State University of New York, College at Buffalo, 1300 Elmwood Ave, Buffalo, NY 14222-1095, USA, and cDepartment of Chemistry & Biochemistry, University of Minnesota Duluth, Duluth, Minnesota 55812-2496, USA
*Correspondence e-mail: nazareay@buffalostate.edu
The title compound, C19H30O9, was prepared by substitution at the C6 position in 1,2;3,4-di-O-isopropylidene-6-O-trifluoromethanesulfonyl-D-galactose using sodium ethoxymalonate in dimethylformamide. The conformation is skew-boat 0S2, slightly distorted towards boat B2,5. The inflexible pyranose structure makes the title compound a suitable intermediate for further synthetic work by keeping stereogenic carbon atoms safe from inversion. Several short intramolecular C—H⋯ O contacts may stabilize the conformation of the molecule. Intermolecular C—H⋯O interactions also occur.
Related literature
For syntheses of this and similar compounds, see: Bouhlal et al. (2001); Doboszewski et al. (1987); Honeyman & Stening (1958); Sugihara et al. (1963); Tipson (1953); Cipolla et al. (1996). For the structures of diisopropylidene-galactopyranose and related compounds, see: Krajewski et al. (1990, 1994); Coutrot et al. (2001); Weaver et al. (2004, 2006); Boeyens et al. (1978); Berces et al. (2001). For conformations of small rings, see: Schwarz (1973); Cremer & Pople (1975); Boeyens (1978); Hill & Reilly (2007); Köll et al. (1994). For analysis of see: Flack (1983); Hooft et al. (2008).
Experimental
Crystal data
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Data collection: CrystalClear-SM Expert (Rigaku, 2009); cell HKL-2000 (Otwinowski & Minor, 1997); data reduction: CrystalClear-SM Expert; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: PLATON (Spek, 2009).
Supporting information
https://doi.org/10.1107/S1600536810046921/zl2327sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810046921/zl2327Isup2.hkl
Synthesis of the title compound was accomplished similar to previuosly published fluorination reaction (Doboszewski et al., 1987). We treated 1,2;3,4-di-O-isopropylidene-6-O-trifluoromethanesulfonyl-D- galactose with sodium ethoxymalonate in dimethylformamide at 333 K; the title compound was isolated in 80% yield (Figure 5). The compound is identical to previously obtained via a free-radical process in low yield (Cipolla et al., 1996). Spontaneous crystallization from a hexane-ethyl acetate system yielded colourless crystals suitable for single-crystal diffractometry (m.p. 331–334 K).
The
of the title compound was known from the synthetic route; it was also examined using Analysis of the using likelihood methods (Hooft et al., 2008) was performed using PLATON (Spek, 2003); 1570 Bijvoet pairs were employed. The results confirmed that the had been correctly assigned: the probability that the structure is inverted is smaller than 10-9 with probability of racemic at 0.002. Because no atom heavier than O is present, the standard deviation of the is relatively high. All H atoms were positioned geometrically and refined using a riding model, with C–H = 0.99–1.03 Å and Uiso(H) = 1.2 or 1.5 Ueq(C). The rotating group model was applied for the methyl groups.The title compound is an intermediate for the synthesis of a wide range of chain-extended galactopyranoses, which in turn are considered as precursors of chiral α-hydroxycarboxylic acids. The stereogenic atom C5 is retained in the target compounds. Knowledge of exact geometry of the intermediate is helpful for better understanding of upcoming steps in this ongoing synthetic project.
To realise these objectives we (BD & PRS) have prepared the title compound by substitution at the C6 position in 1,2;3,4-di-O-isopropylidene-6-O-trifluoromethanesulfonyl-D-galactose using sodium ethoxymalonate. Substitutions at this atom in diisopropylidene-galactose are rather difficult and require prolonged reaction times and/or elevated temperatures (Tipson, 1953, Honeyman & Stening, 1958, Sugihara et al., 1963, Bouhlal et al., 2001). Howeever, by using the best available
a trifluoromethanesulfonate, smooth nucleophilic substitution can been accomplished in less than 10 min (Doboszewski et al., 1987).The α radiation was necessary for determination of the absolute structure.
of 6-deoxy-6-(diethylmalonyl)-1,2;3,4-di-O -isopropylidene-D-galactopyranose is certain from the synthetic route which does not affect asymmetric atoms of the starting compound. Nevertheless, we preferred to receive a direct experimental confirmation using X-ray diffractometry data. Because there are no heavy atoms in a chiral molecule of title compound, Cu KIn the
of title compound (Fig.1), all bond lengths and bond angles have standard dimensions.Fig. 2 shows that the pyranose ring adopts a skew-boat with atoms C1, C3, C4, and C5 being within 0.03–0.08 Å from their mean plane, and O1 and C2 atoms being at 0.633 (2) and -0.557 (2) Å, respectively. Such conformation is named OS2 in the IUPAC notation (Schwarz, 1973). A quantitative analysis of the ring conformations in the titlw compound was performed using the method of Cremer and Pople (Cremer & Pople, 1975, Boeyens, 1978) for the calculation of parameters of puckering. The polar parameters for the pyranose ring are Q = 0.639 (2) Å, Φ = 325.1 (2)°, and θ = 80.3 (2)°. These suggest the conformation as skew-boat 0S2 (Φ = 330°, θ = 90°), slightly distorted towards boat B2,5, (Φ = 300°, θ = 90°); the same conformation is designated as a twist-boat OT2 when using the Boeyenes nomenclature. This conformation is similar to many other known galactopyranoses with two substituent isopropylidene rings (see, for example, POCSUV (Krajewski et al., 1994): Q = 0.632 (5) Å, θ = 82.8 (5)°,Φ = 327.4 (4)°; JERJIUL (Krajewski et al., 1990): Q = 0.631 (5) Å, θ = 79.7 (5)°, Φ = 324.9 (5)°; ICALED (Coutrot et al., 2001): Q = 0.646 (4) Å, θ = 83.9 (4)°, Φ = 334.2 (3)°; BIHZUO (Weaver et al., 2004): Q = 0.661 (2) Å, θ = 81.3 (2)°, Φ = 327.1 (2)°; ADXPOP (Boeyens, Rathbone & Woolard,1978): Q = 0.65 Å, Φ = 329°, θ = 81°). All conformations of substituted compounds are radically different from the chair conformation of unsubstituted α -D-galactopyranose. This is caused by the presence of the two isopropylidene substituents that make the geometry of the pyranose ring more rigid and less sensitive towards any effects of substituents at the remaining C5 position. A detailed discussion of terminology and different puckering coordinates being used to describe six-membered non-aromatic cycles can be found in Hill & Reilly (2007) and Köll et al. (1994).
The same approach yielded the parameters of puckering Q(2) = 0.279 (2) Å, Φ = 283.3 (4)° and Q(2) = 0.234 (2) Å, Φ = 177.1 (7)° for the 1,2- and 3,4- isopropylidene rings. These values correspond to the envelope conformations 4E (Φ = 288°) and E1 (Φ = 180°) with atoms O3 and O4 being out of their corresponding planes by 0.426 (2) and 0.357 (2) Å correspondingly (Fig. 3 and 4). All other atoms in both five-membered rings are located within 0.01 Å from their mean planes.
No classic hydrogen bonds are possible for the title compound. However, several short C—H··· O contacts were detected that possibly stabilize the existing conformation of the molecule (Table 1).
The inflexible pyranose structure makes the title compound a suitable intermediate for further synthetic work by keeping the stereogenic carbon atoms C1—C5 safe from inversion. For the same reason, it is very probable that in solution this molecule will keep almost the same geometry as in the molecular crystal.
For syntheses of this and similar compounds, see: Bouhlal et al. (2001); Doboszewski et al. (1987); Honeyman & Stening (1958); Sugihara et al. (1963); Tipson (1953); Cipolla et al. (1996). For the structures of diisopropylidene-galactopyranose and related compounds, see: Krajewski et al. (1990, 1994); Coutrot et al. (2001); Weaver et al. (2004, 2006); Boeyens et al. (1978); Berces et al. (2001). For conformations of small rings, see: Schwarz (1973); Cremer & Pople (1975); Boeyens (1978); Hill & Reilly (2007); Köll et al. (1994). For analysis of
see: Flack (1983); Hooft et al. (2008).Data collection: CrystalClear-SM Expert (Rigaku, 2009); cell
HKL-2000 (Otwinowski & Minor, 1997); data reduction: CrystalClear-SM Expert (Rigaku, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1999); software used to prepare material for publication: PLATON (Spek, 2009).C19H30O9 | Dx = 1.240 Mg m−3 |
Mr = 402.43 | Melting point: 322 K |
Orthorhombic, P212121 | Cu Kα radiation, λ = 1.54187 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 9579 reflections |
a = 8.3287 (4) Å | θ = 6.7–68.2° |
b = 10.8895 (4) Å | µ = 0.83 mm−1 |
c = 23.7706 (16) Å | T = 292 K |
V = 2155.9 (2) Å3 | Prism, colourless |
Z = 4 | 0.38 × 0.26 × 0.21 mm |
F(000) = 864 |
Rigaku R-AXIS RAPID II imaging plate diffractometer | 3745 independent reflections |
Radiation source: fine-focus sealed tube | 2824 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.075 |
Detector resolution: 10 pixels mm-1 | θmax = 66.5°, θmin = 6.7° |
ω scans | h = −6→9 |
Absorption correction: multi-scan (ABSCOR; Higashi,1995) | k = −12→10 |
Tmin = 0.822, Tmax = 0.840 | l = −28→19 |
9353 measured reflections |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.040 | w = 1/[σ2(Fo2) + (0.0285P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.096 | (Δ/σ)max < 0.001 |
S = 1.02 | Δρmax = 0.19 e Å−3 |
3745 reflections | Δρmin = −0.15 e Å−3 |
275 parameters | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0057 (5) |
Primary atom site location: structure-invariant direct methods | Absolute structure: Flack (1983), 1607 Friedel pairs |
Secondary atom site location: difference Fourier map | Absolute structure parameter: 0.06 (18) |
C19H30O9 | V = 2155.9 (2) Å3 |
Mr = 402.43 | Z = 4 |
Orthorhombic, P212121 | Cu Kα radiation |
a = 8.3287 (4) Å | µ = 0.83 mm−1 |
b = 10.8895 (4) Å | T = 292 K |
c = 23.7706 (16) Å | 0.38 × 0.26 × 0.21 mm |
Rigaku R-AXIS RAPID II imaging plate diffractometer | 3745 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi,1995) | 2824 reflections with I > 2σ(I) |
Tmin = 0.822, Tmax = 0.840 | Rint = 0.075 |
9353 measured reflections |
R[F2 > 2σ(F2)] = 0.040 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.096 | Δρmax = 0.19 e Å−3 |
S = 1.02 | Δρmin = −0.15 e Å−3 |
3745 reflections | Absolute structure: Flack (1983), 1607 Friedel pairs |
275 parameters | Absolute structure parameter: 0.06 (18) |
0 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.30842 (18) | 0.05824 (11) | 0.37716 (6) | 0.0531 (4) | |
O2 | 0.2263 (2) | 0.25329 (12) | 0.35151 (6) | 0.0653 (5) | |
O3 | 0.2044 (2) | 0.30221 (12) | 0.44385 (6) | 0.0646 (5) | |
O4 | 0.0989 (2) | −0.00622 (15) | 0.48415 (7) | 0.0747 (5) | |
O5 | 0.3563 (2) | −0.07330 (14) | 0.48515 (7) | 0.0817 (6) | |
O6 | 0.6685 (2) | 0.16820 (13) | 0.27264 (7) | 0.0718 (5) | |
O7 | 0.7237 (2) | 0.22413 (15) | 0.36113 (7) | 0.0852 (6) | |
O8 | 0.7062 (2) | −0.17738 (13) | 0.31233 (6) | 0.0666 (5) | |
O9 | 0.8976 (2) | −0.03812 (18) | 0.32008 (11) | 0.1155 (9) | |
C1 | 0.1819 (3) | 0.14252 (17) | 0.37891 (9) | 0.0523 (6) | |
H1A | 0.088 (2) | 0.1070 (8) | 0.3597 (4) | 0.063* | |
C2 | 0.1329 (3) | 0.18443 (17) | 0.43770 (9) | 0.0573 (6) | |
H2A | 0.012 (3) | 0.1918 (2) | 0.43999 (11) | 0.069* | |
C3 | 0.1939 (3) | 0.10213 (19) | 0.48485 (10) | 0.0600 (6) | |
H3A | 0.1836 (4) | 0.1456 (10) | 0.5227 (8) | 0.072* | |
C4 | 0.3665 (3) | 0.0557 (2) | 0.47632 (9) | 0.0566 (6) | |
H4A | 0.4367 (16) | 0.0921 (8) | 0.5044 (6) | 0.068* | |
C5 | 0.4315 (3) | 0.0817 (2) | 0.41783 (9) | 0.0490 (5) | |
H5A | 0.4630 (7) | 0.1708 (18) | 0.41554 (10) | 0.059* | |
C6 | 0.2124 (3) | 0.35512 (18) | 0.38911 (9) | 0.0580 (6) | |
C7 | 0.3592 (3) | 0.4335 (2) | 0.38497 (12) | 0.0860 (10) | |
H7A | 0.3572 (11) | 0.4945 (14) | 0.4142 (7) | 0.129* | |
H7B | 0.3615 (12) | 0.4733 (15) | 0.3489 (6) | 0.129* | |
H7C | 0.4532 (15) | 0.3831 (8) | 0.3892 (8) | 0.129* | |
C8 | 0.0607 (3) | 0.4254 (2) | 0.37542 (11) | 0.0742 (8) | |
H8A | 0.0457 (11) | 0.4951 (13) | 0.4040 (6) | 0.111* | |
H8B | −0.0360 (13) | 0.3671 (8) | 0.3773 (7) | 0.111* | |
H8C | 0.0694 (9) | 0.4617 (14) | 0.3357 (6) | 0.111* | |
C9 | 0.1971 (3) | −0.1063 (2) | 0.49989 (10) | 0.0657 (7) | |
C10 | 0.1486 (5) | −0.2177 (2) | 0.46606 (14) | 0.1124 (13) | |
H10A | 0.034 (2) | −0.2405 (13) | 0.4754 (7) | 0.169* | |
H10B | 0.222 (2) | −0.2886 (14) | 0.4756 (8) | 0.169* | |
H10C | 0.157 (3) | −0.1985 (8) | 0.4246 (7) | 0.169* | |
C11 | 0.1883 (4) | −0.1306 (3) | 0.56235 (11) | 0.0901 (10) | |
H11A | 0.0735 (17) | −0.1545 (17) | 0.5730 (2) | 0.135* | |
H11B | 0.221 (2) | −0.0531 (13) | 0.5838 (3) | 0.135* | |
H11C | 0.265 (2) | −0.2007 (15) | 0.5725 (2) | 0.135* | |
C12 | 0.5762 (3) | 0.00309 (19) | 0.40257 (9) | 0.0557 (6) | |
H12A | 0.5494 (4) | −0.0868 (13) | 0.40954 (15) | 0.067* | |
H12B | 0.6699 (14) | 0.0260 (3) | 0.4279 (4) | 0.067* | |
C13 | 0.6261 (3) | 0.01977 (16) | 0.34089 (9) | 0.0510 (6) | |
H13A | 0.535 (2) | 0.0017 (4) | 0.3179 (5) | 0.061* | |
C14 | 0.6788 (3) | 0.1493 (2) | 0.32781 (11) | 0.0585 (6) | |
C15 | 0.7163 (4) | 0.2883 (2) | 0.25156 (13) | 0.0870 (10) | |
H15A | 0.826 (2) | 0.3111 (5) | 0.2665 (3) | 0.104* | |
H15B | 0.6368 (15) | 0.3532 (13) | 0.2641 (3) | 0.104* | |
C16 | 0.7196 (4) | 0.2807 (2) | 0.18966 (12) | 0.0887 (10) | |
H16A | 0.799 (2) | 0.2184 (16) | 0.1779 (2) | 0.133* | |
H16B | 0.750 (2) | 0.3614 (13) | 0.1739 (3) | 0.133* | |
H16C | 0.6122 (18) | 0.2572 (17) | 0.1757 (3) | 0.133* | |
C17 | 0.7604 (3) | −0.0665 (2) | 0.32388 (10) | 0.0608 (6) | |
C18 | 0.8256 (3) | −0.2666 (2) | 0.29360 (12) | 0.0725 (8) | |
H18A | 0.9058 (14) | −0.2830 (3) | 0.3248 (5) | 0.087* | |
H18B | 0.8859 (11) | −0.2336 (6) | 0.2598 (5) | 0.087* | |
C19 | 0.7401 (4) | −0.3825 (2) | 0.27835 (11) | 0.0828 (10) | |
H19A | 0.6860 (18) | −0.4159 (10) | 0.3119 (5) | 0.124* | |
H19B | 0.8182 (11) | −0.4430 (10) | 0.2641 (7) | 0.124* | |
H19C | 0.6597 (18) | −0.3651 (4) | 0.2490 (6) | 0.124* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0620 (10) | 0.0461 (7) | 0.0511 (9) | 0.0023 (8) | −0.0101 (7) | −0.0076 (7) |
O2 | 0.0976 (13) | 0.0470 (8) | 0.0515 (9) | 0.0008 (8) | 0.0044 (9) | 0.0014 (6) |
O3 | 0.0955 (13) | 0.0472 (8) | 0.0510 (9) | 0.0018 (9) | −0.0093 (9) | −0.0041 (7) |
O4 | 0.0744 (13) | 0.0687 (10) | 0.0811 (13) | −0.0030 (10) | 0.0129 (9) | 0.0232 (9) |
O5 | 0.0809 (13) | 0.0615 (9) | 0.1028 (14) | 0.0083 (10) | 0.0273 (11) | 0.0349 (9) |
O6 | 0.0982 (15) | 0.0526 (8) | 0.0645 (11) | −0.0142 (9) | 0.0074 (10) | 0.0135 (8) |
O7 | 0.1065 (16) | 0.0676 (10) | 0.0814 (13) | −0.0359 (11) | 0.0086 (12) | −0.0092 (9) |
O8 | 0.0630 (11) | 0.0515 (8) | 0.0854 (12) | −0.0037 (9) | 0.0082 (10) | −0.0091 (8) |
O9 | 0.0547 (12) | 0.0826 (12) | 0.209 (3) | −0.0130 (11) | 0.0071 (14) | −0.0325 (14) |
C1 | 0.0597 (15) | 0.0464 (11) | 0.0508 (13) | −0.0018 (12) | −0.0106 (12) | −0.0010 (9) |
C2 | 0.0730 (18) | 0.0486 (12) | 0.0504 (14) | 0.0037 (12) | 0.0039 (12) | −0.0024 (10) |
C3 | 0.0764 (18) | 0.0570 (12) | 0.0466 (14) | 0.0017 (14) | 0.0079 (13) | 0.0032 (10) |
C4 | 0.0679 (17) | 0.0551 (12) | 0.0467 (13) | −0.0024 (13) | −0.0017 (12) | 0.0068 (11) |
C5 | 0.0588 (15) | 0.0430 (10) | 0.0452 (13) | −0.0078 (11) | −0.0057 (11) | 0.0016 (9) |
C6 | 0.0759 (18) | 0.0446 (11) | 0.0534 (14) | 0.0025 (13) | −0.0021 (13) | 0.0002 (10) |
C7 | 0.087 (2) | 0.0612 (15) | 0.110 (2) | −0.0130 (16) | −0.0115 (17) | 0.0115 (15) |
C8 | 0.0827 (19) | 0.0598 (14) | 0.0800 (19) | 0.0081 (15) | −0.0057 (14) | 0.0083 (13) |
C9 | 0.0756 (19) | 0.0581 (13) | 0.0635 (16) | 0.0010 (14) | 0.0195 (15) | 0.0125 (11) |
C10 | 0.146 (4) | 0.0824 (19) | 0.108 (3) | −0.020 (2) | 0.013 (2) | −0.0156 (18) |
C11 | 0.109 (2) | 0.0972 (19) | 0.0644 (17) | 0.015 (2) | 0.0238 (17) | 0.0259 (15) |
C12 | 0.0600 (15) | 0.0517 (11) | 0.0555 (15) | −0.0035 (13) | −0.0012 (12) | 0.0091 (10) |
C13 | 0.0539 (14) | 0.0458 (11) | 0.0534 (14) | −0.0058 (11) | 0.0009 (11) | 0.0032 (10) |
C14 | 0.0595 (17) | 0.0515 (12) | 0.0645 (16) | −0.0050 (12) | 0.0059 (13) | 0.0027 (11) |
C15 | 0.113 (3) | 0.0524 (13) | 0.096 (2) | −0.0125 (16) | 0.026 (2) | 0.0189 (14) |
C16 | 0.091 (2) | 0.0784 (17) | 0.096 (2) | 0.0061 (17) | 0.0249 (19) | 0.0356 (16) |
C17 | 0.0568 (17) | 0.0571 (13) | 0.0684 (16) | −0.0068 (13) | 0.0037 (13) | −0.0003 (12) |
C18 | 0.0680 (19) | 0.0702 (15) | 0.0794 (18) | 0.0135 (16) | 0.0072 (15) | −0.0077 (13) |
C19 | 0.109 (3) | 0.0585 (14) | 0.0807 (19) | 0.0077 (16) | −0.0041 (17) | −0.0091 (13) |
O1—C1 | 1.398 (2) | C7—H7C | 0.9614 |
O1—C5 | 1.432 (2) | C8—H8A | 1.0264 |
O2—C1 | 1.420 (2) | C8—H8B | 1.0264 |
O2—C6 | 1.429 (2) | C8—H8C | 1.0264 |
O3—C2 | 1.422 (2) | C9—C11 | 1.510 (3) |
O3—C6 | 1.425 (2) | C9—C10 | 1.511 (4) |
O4—C9 | 1.413 (3) | C10—H10A | 1.0094 |
O4—C3 | 1.421 (2) | C10—H10B | 1.0094 |
O5—C9 | 1.418 (3) | C10—H10C | 1.0094 |
O5—C4 | 1.423 (3) | C11—H11A | 1.0229 |
O6—C14 | 1.330 (3) | C11—H11B | 1.0229 |
O6—C15 | 1.456 (2) | C11—H11C | 1.0229 |
O7—C14 | 1.196 (3) | C12—C13 | 1.535 (3) |
O8—C17 | 1.317 (3) | C12—H12A | 1.0171 |
O8—C18 | 1.460 (3) | C12—H12B | 1.0171 |
O9—C17 | 1.187 (3) | C13—C14 | 1.509 (3) |
C1—C2 | 1.526 (3) | C13—C17 | 1.515 (3) |
C1—H1A | 0.9878 | C13—H13A | 0.9571 |
C2—C3 | 1.523 (3) | C15—C16 | 1.474 (4) |
C2—H2A | 1.0091 | C15—H15A | 1.0130 |
C3—C4 | 1.537 (3) | C15—H15B | 1.0130 |
C3—H3A | 1.0200 | C16—H16A | 0.9879 |
C4—C5 | 1.518 (3) | C16—H16B | 0.9879 |
C4—H4A | 0.9713 | C16—H16C | 0.9879 |
C5—C12 | 1.522 (3) | C18—C19 | 1.494 (3) |
C5—H5A | 1.0065 | C18—H18A | 1.0133 |
C6—C7 | 1.494 (3) | C18—H18B | 1.0133 |
C6—C8 | 1.513 (3) | C19—H19A | 0.9857 |
C7—H7A | 0.9614 | C19—H19B | 0.9857 |
C7—H7B | 0.9614 | C19—H19C | 0.9857 |
C1—O1—C5 | 113.72 (15) | O4—C9—C10 | 108.9 (2) |
C1—O2—C6 | 110.56 (16) | O5—C9—C10 | 108.8 (2) |
C2—O3—C6 | 106.90 (15) | C11—C9—C10 | 111.7 (2) |
C9—O4—C3 | 108.33 (17) | C9—C10—H10A | 109.5 |
C9—O5—C4 | 110.03 (18) | C9—C10—H10B | 109.5 |
C14—O6—C15 | 117.44 (19) | H10A—C10—H10B | 109.5 |
C17—O8—C18 | 116.12 (19) | C9—C10—H10C | 109.5 |
O1—C1—O2 | 110.33 (18) | H10A—C10—H10C | 109.5 |
O1—C1—C2 | 115.16 (18) | H10B—C10—H10C | 109.5 |
O2—C1—C2 | 103.64 (15) | C9—C11—H11A | 109.5 |
O1—C1—H1A | 109.2 | C9—C11—H11B | 109.5 |
O2—C1—H1A | 109.2 | H11A—C11—H11B | 109.5 |
C2—C1—H1A | 109.2 | C9—C11—H11C | 109.5 |
O3—C2—C3 | 108.38 (19) | H11A—C11—H11C | 109.5 |
O3—C2—C1 | 104.60 (18) | H11B—C11—H11C | 109.5 |
C3—C2—C1 | 114.14 (18) | C5—C12—C13 | 112.06 (17) |
O3—C2—H2A | 109.8 | C5—C12—H12A | 109.2 |
C3—C2—H2A | 109.8 | C13—C12—H12A | 109.2 |
C1—C2—H2A | 109.8 | C5—C12—H12B | 109.2 |
O4—C3—C2 | 107.09 (19) | C13—C12—H12B | 109.2 |
O4—C3—C4 | 104.26 (18) | H12A—C12—H12B | 107.9 |
C2—C3—C4 | 114.1 (2) | C14—C13—C17 | 108.06 (19) |
O4—C3—H3A | 110.4 | C14—C13—C12 | 112.71 (17) |
C2—C3—H3A | 110.4 | C17—C13—C12 | 112.42 (17) |
C4—C3—H3A | 110.4 | C14—C13—H13A | 107.8 |
O5—C4—C5 | 109.92 (18) | C17—C13—H13A | 107.8 |
O5—C4—C3 | 104.44 (18) | C12—C13—H13A | 107.8 |
C5—C4—C3 | 113.11 (19) | O7—C14—O6 | 124.5 (2) |
O5—C4—H4A | 109.7 | O7—C14—C13 | 126.2 (2) |
C5—C4—H4A | 109.7 | O6—C14—C13 | 109.2 (2) |
C3—C4—H4A | 109.7 | O6—C15—C16 | 107.3 (2) |
O1—C5—C4 | 109.26 (18) | O6—C15—H15A | 110.2 |
O1—C5—C12 | 107.79 (17) | C16—C15—H15A | 110.2 |
C4—C5—C12 | 113.28 (17) | O6—C15—H15B | 110.2 |
O1—C5—H5A | 108.8 | C16—C15—H15B | 110.2 |
C4—C5—H5A | 108.8 | H15A—C15—H15B | 108.5 |
C12—C5—H5A | 108.8 | C15—C16—H16A | 109.5 |
O3—C6—O2 | 105.14 (15) | C15—C16—H16B | 109.5 |
O3—C6—C7 | 109.3 (2) | H16A—C16—H16B | 109.5 |
O2—C6—C7 | 109.6 (2) | C15—C16—H16C | 109.5 |
O3—C6—C8 | 111.2 (2) | H16A—C16—H16C | 109.5 |
O2—C6—C8 | 109.00 (19) | H16B—C16—H16C | 109.5 |
C7—C6—C8 | 112.36 (18) | O9—C17—O8 | 123.5 (2) |
C6—C7—H7A | 109.5 | O9—C17—C13 | 124.7 (2) |
C6—C7—H7B | 109.5 | O8—C17—C13 | 111.8 (2) |
H7A—C7—H7B | 109.5 | O8—C18—C19 | 108.2 (2) |
C6—C7—H7C | 109.5 | O8—C18—H18A | 110.1 |
H7A—C7—H7C | 109.5 | C19—C18—H18A | 110.1 |
H7B—C7—H7C | 109.5 | O8—C18—H18B | 110.1 |
C6—C8—H8A | 109.5 | C19—C18—H18B | 110.1 |
C6—C8—H8B | 109.5 | H18A—C18—H18B | 108.4 |
H8A—C8—H8B | 109.5 | C18—C19—H19A | 109.5 |
C6—C8—H8C | 109.5 | C18—C19—H19B | 109.5 |
H8A—C8—H8C | 109.5 | H19A—C19—H19B | 109.5 |
H8B—C8—H8C | 109.5 | C18—C19—H19C | 109.5 |
O4—C9—O5 | 106.31 (17) | H19A—C19—H19C | 109.5 |
O4—C9—C11 | 111.6 (2) | H19B—C19—H19C | 109.5 |
O5—C9—C11 | 109.4 (2) | ||
C5—O1—C1—O2 | 78.7 (2) | C2—O3—C6—C7 | −146.7 (2) |
C5—O1—C1—C2 | −38.2 (2) | C2—O3—C6—C8 | 88.7 (2) |
C6—O2—C1—O1 | −122.13 (19) | C1—O2—C6—O3 | 16.5 (3) |
C6—O2—C1—C2 | 1.7 (3) | C1—O2—C6—C7 | 133.8 (2) |
C6—O3—C2—C3 | 152.18 (19) | C1—O2—C6—C8 | −102.8 (2) |
C6—O3—C2—C1 | 30.0 (2) | C3—O4—C9—O5 | −26.3 (2) |
O1—C1—C2—O3 | 101.3 (2) | C3—O4—C9—C11 | 93.0 (3) |
O2—C1—C2—O3 | −19.2 (2) | C3—O4—C9—C10 | −143.3 (2) |
O1—C1—C2—C3 | −16.9 (3) | C4—O5—C9—O4 | 17.1 (3) |
O2—C1—C2—C3 | −137.5 (2) | C4—O5—C9—C11 | −103.5 (2) |
C9—O4—C3—C2 | 145.74 (19) | C4—O5—C9—C10 | 134.2 (2) |
C9—O4—C3—C4 | 24.4 (2) | O1—C5—C12—C13 | 51.9 (2) |
O3—C2—C3—O4 | 169.21 (18) | C4—C5—C12—C13 | 172.91 (19) |
C1—C2—C3—O4 | −74.7 (3) | C5—C12—C13—C14 | 62.8 (2) |
O3—C2—C3—C4 | −76.0 (2) | C5—C12—C13—C17 | −174.81 (18) |
C1—C2—C3—C4 | 40.2 (3) | C15—O6—C14—O7 | 0.4 (4) |
C9—O5—C4—C5 | −123.7 (2) | C15—O6—C14—C13 | −179.3 (2) |
C9—O5—C4—C3 | −2.1 (3) | C17—C13—C14—O7 | −104.0 (3) |
O4—C3—C4—O5 | −13.5 (2) | C12—C13—C14—O7 | 20.9 (4) |
C2—C3—C4—O5 | −129.97 (19) | C17—C13—C14—O6 | 75.7 (3) |
O4—C3—C4—C5 | 106.0 (2) | C12—C13—C14—O6 | −159.4 (2) |
C2—C3—C4—C5 | −10.5 (3) | C14—O6—C15—C16 | 171.0 (2) |
C1—O1—C5—C4 | 69.3 (2) | C18—O8—C17—O9 | −0.5 (4) |
C1—O1—C5—C12 | −167.25 (15) | C18—O8—C17—C13 | 177.98 (19) |
O5—C4—C5—O1 | 74.9 (2) | C14—C13—C17—O9 | 23.8 (3) |
C3—C4—C5—O1 | −41.4 (2) | C12—C13—C17—O9 | −101.2 (3) |
O5—C4—C5—C12 | −45.3 (3) | C14—C13—C17—O8 | −154.6 (2) |
C3—C4—C5—C12 | −161.60 (18) | C12—C13—C17—O8 | 80.4 (2) |
C2—O3—C6—O2 | −29.2 (3) | C17—O8—C18—C19 | −175.6 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
C1—H1A···O9i | 0.98 | 2.43 | 3.381 (3) | 163 |
C5—H5A···O7 | 1.01 | 2.59 | 3.185 (3) | 117 |
C8—H8B···O7i | 1.03 | 2.56 | 3.577 (3) | 169 |
C12—H12A···O5 | 1.02 | 2.42 | 2.811 (3) | 102 |
C13—H13A···O1 | 0.96 | 2.43 | 2.814 (3) | 103 |
C16—H16B···O1ii | 0.99 | 2.51 | 3.422 (3) | 153 |
Symmetry codes: (i) x−1, y, z; (ii) −x+1, y+1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C19H30O9 |
Mr | 402.43 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 292 |
a, b, c (Å) | 8.3287 (4), 10.8895 (4), 23.7706 (16) |
V (Å3) | 2155.9 (2) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.83 |
Crystal size (mm) | 0.38 × 0.26 × 0.21 |
Data collection | |
Diffractometer | Rigaku R-AXIS RAPID II imaging plate |
Absorption correction | Multi-scan (ABSCOR; Higashi,1995) |
Tmin, Tmax | 0.822, 0.840 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9353, 3745, 2824 |
Rint | 0.075 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.040, 0.096, 1.02 |
No. of reflections | 3745 |
No. of parameters | 275 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.19, −0.15 |
Absolute structure | Flack (1983), 1607 Friedel pairs |
Absolute structure parameter | 0.06 (18) |
Computer programs: CrystalClear-SM Expert (Rigaku, 2009), HKL-2000 (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1999), PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
C1—H1A···O9i | 0.98 | 2.43 | 3.381 (3) | 163 |
C5—H5A···O7 | 1.01 | 2.59 | 3.185 (3) | 117 |
C8—H8B···O7i | 1.03 | 2.56 | 3.577 (3) | 169 |
C12—H12A···O5 | 1.02 | 2.42 | 2.811 (3) | 102 |
C13—H13A···O1 | 0.96 | 2.43 | 2.814 (3) | 103 |
C16—H16B···O1ii | 0.99 | 2.51 | 3.422 (3) | 153 |
Symmetry codes: (i) x−1, y, z; (ii) −x+1, y+1/2, −z+1/2. |
Acknowledgements
This study was supported by the NSF (grant CHE-0922366 for X-ray diffractometer) and SUNY (grant No 1073053).
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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.
The title compound is an intermediate for the synthesis of a wide range of chain-extended galactopyranoses, which in turn are considered as precursors of chiral α-hydroxycarboxylic acids. The stereogenic atom C5 is retained in the target compounds. Knowledge of exact geometry of the intermediate is helpful for better understanding of upcoming steps in this ongoing synthetic project.
To realise these objectives we (BD & PRS) have prepared the title compound by substitution at the C6 position in 1,2;3,4-di-O-isopropylidene-6-O-trifluoromethanesulfonyl-D-galactose using sodium ethoxymalonate. Substitutions at this atom in diisopropylidene-galactose are rather difficult and require prolonged reaction times and/or elevated temperatures (Tipson, 1953, Honeyman & Stening, 1958, Sugihara et al., 1963, Bouhlal et al., 2001). Howeever, by using the best available leaving group, a trifluoromethanesulfonate, smooth nucleophilic substitution can been accomplished in less than 10 min (Doboszewski et al., 1987).
The absolute structure of 6-deoxy-6-(diethylmalonyl)-1,2;3,4-di-O -isopropylidene-D-galactopyranose is certain from the synthetic route which does not affect asymmetric atoms of the starting compound. Nevertheless, we preferred to receive a direct experimental confirmation using X-ray diffractometry data. Because there are no heavy atoms in a chiral molecule of title compound, Cu Kα radiation was necessary for determination of the absolute structure.
In the crystal structure of title compound (Fig.1), all bond lengths and bond angles have standard dimensions.
Fig. 2 shows that the pyranose ring adopts a skew-boat with atoms C1, C3, C4, and C5 being within 0.03–0.08 Å from their mean plane, and O1 and C2 atoms being at 0.633 (2) and -0.557 (2) Å, respectively. Such conformation is named OS2 in the IUPAC notation (Schwarz, 1973). A quantitative analysis of the ring conformations in the titlw compound was performed using the method of Cremer and Pople (Cremer & Pople, 1975, Boeyens, 1978) for the calculation of parameters of puckering. The polar parameters for the pyranose ring are Q = 0.639 (2) Å, Φ = 325.1 (2)°, and θ = 80.3 (2)°. These suggest the conformation as skew-boat 0S2 (Φ = 330°, θ = 90°), slightly distorted towards boat B2,5, (Φ = 300°, θ = 90°); the same conformation is designated as a twist-boat OT2 when using the Boeyenes nomenclature. This conformation is similar to many other known galactopyranoses with two substituent isopropylidene rings (see, for example, POCSUV (Krajewski et al., 1994): Q = 0.632 (5) Å, θ = 82.8 (5)°,Φ = 327.4 (4)°; JERJIUL (Krajewski et al., 1990): Q = 0.631 (5) Å, θ = 79.7 (5)°, Φ = 324.9 (5)°; ICALED (Coutrot et al., 2001): Q = 0.646 (4) Å, θ = 83.9 (4)°, Φ = 334.2 (3)°; BIHZUO (Weaver et al., 2004): Q = 0.661 (2) Å, θ = 81.3 (2)°, Φ = 327.1 (2)°; ADXPOP (Boeyens, Rathbone & Woolard,1978): Q = 0.65 Å, Φ = 329°, θ = 81°). All conformations of substituted compounds are radically different from the chair conformation of unsubstituted α -D-galactopyranose. This is caused by the presence of the two isopropylidene substituents that make the geometry of the pyranose ring more rigid and less sensitive towards any effects of substituents at the remaining C5 position. A detailed discussion of terminology and different puckering coordinates being used to describe six-membered non-aromatic cycles can be found in Hill & Reilly (2007) and Köll et al. (1994).
The same approach yielded the parameters of puckering Q(2) = 0.279 (2) Å, Φ = 283.3 (4)° and Q(2) = 0.234 (2) Å, Φ = 177.1 (7)° for the 1,2- and 3,4- isopropylidene rings. These values correspond to the envelope conformations 4E (Φ = 288°) and E1 (Φ = 180°) with atoms O3 and O4 being out of their corresponding planes by 0.426 (2) and 0.357 (2) Å correspondingly (Fig. 3 and 4). All other atoms in both five-membered rings are located within 0.01 Å from their mean planes.
No classic hydrogen bonds are possible for the title compound. However, several short C—H··· O contacts were detected that possibly stabilize the existing conformation of the molecule (Table 1).
The inflexible pyranose structure makes the title compound a suitable intermediate for further synthetic work by keeping the stereogenic carbon atoms C1—C5 safe from inversion. For the same reason, it is very probable that in solution this molecule will keep almost the same geometry as in the molecular crystal.