An ortho­rhom­bic polymorph of 6-de­oxy-6-iodo-1,2:3,4-di-O-isopropyl­idene-α-d-galactopyran­oside

Hoong-Kun Fun; Wei-Ching Liew; Sankappa Rai; Prakash Shetty; Arun M Isloor

doi:10.1107/S1600536809029031

. 2009 Jul 25;65(Pt 8):o1999–o2000. doi: 10.1107/S1600536809029031

An orthorhombic polymorph of 6-deoxy-6-iodo-1,2:3,4-di-O-isopropylidene-α-d-galactopyranoside

Hoong-Kun Fun ^a,^*,^‡, Wei-Ching Liew ^a, Sankappa Rai ^b, Prakash Shetty ^c, Arun M Isloor ^d

PMCID: PMC2977305 PMID: 21583671

Abstract

The title compound, C₁₂H₁₉IO₅, is the orthorhombic polymorph of a previously reported monoclinic form [Krajewski et al. (1987 ▶). Bull. Pol. Acad. Sci. Chem. 35, 91–102]. The dihedral angles between the six-membered ring and the two five-membered rings are 67.66 (14) and 71.79 (13)°, whereas the dihedral angle between the five-membered rings is 74.41 (12)°, indicating that all three rings are twisted from each other. The six-membered ring has a twist-boat conformation while both of the five-membered rings have envelope conformations. The crystal structure is stabilized by a network of C—H⋯O contacts linking the molecules into a two-dimensional array parallel to the ab plane.

Related literature

For the monoclinic polymorph of the title compound, see: Krajewski et al. (1987 ▶). For the synthesis and biological evaluation of 6-substituted purines, see: Gambogi Braga et al. (2007 ▶). For halogenation reagent systems, see: Classon et al. (1988 ▶). For the synthesis of perosamine derivatives, see: Stevens et al. (1970 ▶). For the synthesis of labilose, see: Westwood et al. (1967 ▶). For ring conformations and ring puckering analysis, see: Boeyens (1978 ▶); Cremer & Pople (1975 ▶). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

C₁₂H₁₉IO₅
M _r = 370.17
Orthorhombic,
a = 7.3595 (1) Å
b = 11.5145 (2) Å
c = 16.9945 (2) Å
V = 1440.13 (4) Å³
Z = 4
Mo Kα radiation
μ = 2.23 mm⁻¹
T = 100 K
0.17 × 0.11 × 0.11 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.703, T _max = 0.785
27359 measured reflections
7509 independent reflections
6211 reflections with I > 2σ(I)
R _int = 0.046

Refinement

R[F ² > 2σ(F ²)] = 0.035
wR(F ²) = 0.096
S = 1.07
7509 reflections
167 parameters
H-atom parameters constrained
Δρ_max = 0.87 e Å⁻³
Δρ_min = −1.24 e Å⁻³
Absolute structure: Flack (1983 ▶), 3286 Friedel pairs
Flack parameter: −0.020 (19)

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809029031/tk2509sup1.cif

e-65-o1999-sup1.cif^{(17.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809029031/tk2509Isup2.hkl

e-65-o1999-Isup2.hkl^{(367.4KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8B⋯O2ⁱ	0.97	2.42	3.377 (3)	169
C12—H12C⋯O2ⁱⁱ	0.96	2.60	3.477 (4)	152

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

HKF and WCL thank Universiti Sains Malaysia (USM) for a Research University Golden Goose Grant (No. 1001/PFIZIK/811012). WCL thanks USM for a student assistantship. AMI is grateful to the Director, NITK, Surathkal, India, for providing research facilities

supplementary crystallographic information

Comment

Libilomycin, an antibiotic which inhibits the growth of Gram-positive bacteria (Westwood et al., 1967) and which is effective against certain tumor cells, is produced by the microorganism, streptomyces albosporeas (Stevens et al., 1970), and contains 6-iodo,6-deoxy-1,2,3,4-di-O-isopropylidine-α-D-galactopyranoside as a part of its structure (Classon et al., 1988). These intermediates are used for the synthesis of 6-substituted purines which show high activity against Leishmania amazonensis (Gambogi Braga et al., 2007). These results prompted us to synthesize the title compound, (I).

Compound (I), Fig. 1, crystallized in the orthorhombic space group P2₁2₁2₁ but has been reported previously (Krajewski et al., 1987) in the monoclinic space group P2₁, with a = 11.157 (2) Å, b = 20.047 (4) Å, c = 14.188 (2) Å and β = 107.67 (1)°. The dihedral angles between the six-membered ring systems, ring A (C1/C3/C4/C6/C7/O5), and the five-membered ring systems [rings B (C1—C3/O1—O2) and C (C4—C6/O3—O4)] are 67.66 (14)° and 71.79 (13)°, repectively. Moreover, the dihedral angle between rings B and C is 74.41 (12)° indicating that all the three rings are twisted from each other. Ring A adopts the twist-boat conformation (Boeyens, 1978; Cremer & Pople, 1975) with puckering amplitude Q = 0.629 (2) Å, φ = 75.3 (3)° and θ = 325.6 (2)°. On the other hand, each of rings B and C adopt an envelope conformation with flap atoms O2 and C5, respectively, but having different puckering parameters. For ring B, the puckering amplitude Q = 0.285 (2) Å and φ = 294.9 (5)° whereas for ring C, the puckering amplitude Q = 0.323 (3) Å and φ = 150.8 (4)°.

The crystal packing (Fig. 2 & Fig. 3) is consolidated by C8—H8B···O2 and C12—H12C···O2 contacts (Table 1) that link the molecules into a 2-D array parallel to the ab plane.

Experimental

Triphenylphosphine (0.53 g, 1.9 mmol) and imidazole (0.4 g, 5.7 mmol) was added to the mixture of 1,2,3,4-di-O-isopropylidine-α-D-galactopyranoside (0.5 g, 1.9 mmol) in toluene: acetonitrile (2: 1, 10 ml). The mixture was heated to 70 °C. Iodine (0.6 g, 3.8 mmol) was then added portion-wise for a period of 30 min and mixture was further stirred for 2 hours. The completion of the reaction was confirmed by TLC (30% EtOAc/hexane, R_f - 0.6). The brown reaction mixture was concentrated under vacuum and the residue was purified by column chromatography using 25% ethylacetate in petroleum ether to get desired compound as white crystals. (Yield 600 mg, 83%, m.p. 334–336 K).