2-O-Benzhydryl-3,4-(S)-O-benzyl­idene-d-xylono-1,4-lactone

Sarah F Jenkinson; Sebastian D Rule; Kathrine V Booth; George W J Fleet; David J Watkin; Sigthor Petursson

doi:10.1107/S1600536808012567

. 2008 May 7;64(Pt 6):o1012. doi: 10.1107/S1600536808012567

2-O-Benzhydryl-3,4-(S)-O-benzylidene-d-xylono-1,4-lactone

Sarah F Jenkinson ^a,^*, Sebastian D Rule ^a, Kathrine V Booth ^a, George W J Fleet ^a, David J Watkin ^b, Sigthor Petursson ^c

PMCID: PMC2961596 PMID: 21202537

Abstract

X-ray crystallography unequivocally shows that protection of the free hydroxyl group of 3,5-O-benzylidene-d-xylono-1,4-lactone with diphenyldiazomethane proceeded smoothly to give the title compound, C₂₅H₂₂O₅, with no accompanying epimerization. Unlike the analogously protected lyxono lactone, the isomeric xylono lactone has two molecules present in the asymmetric unit (Z′ = 2). The 5-ring lactones adopt envelope conformations and the 6-ring ketals adopt chair conformations.

Related literature

For related literature, see: Collins & Ferrier (1995 ▶); Draths et al. (1992 ▶); Jackson et al. (1982 ▶); Petursson & Webber (1982 ▶); Petursson et al. (2007 ▶); Petursson (2001 ▶, 2003 ▶); Best et al. (2008 ▶); Jenkinson et al. (2008 ▶); Görbitz (1999 ▶).

Experimental

Crystal data

C₂₅H₂₂O₅
M _r = 402.45
Monoclinic,
a = 14.8159 (3) Å
b = 9.1959 (2) Å
c = 15.0797 (2) Å
β = 93.7245 (12)°
V = 2050.20 (7) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 150 K
0.80 × 0.30 × 0.10 mm

Data collection

Nonius KappaCCD area-detector diffractometer
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997 ▶) T _min = 0.55, T _max = 0.99
25081 measured reflections
4938 independent reflections
3950 reflections with I > 2σ(I)
R _int = 0.047

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.101
S = 0.89
4938 reflections
542 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.25 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: COLLECT (Nonius, 2001 ▶).; cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997 ▶); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994 ▶); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003 ▶); molecular graphics: CAMERON (Watkin et al., 1996 ▶); software used to prepare material for publication: CRYSTALS.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808012567/lh2623sup1.cif

e-64-o1012-sup1.cif^{(29.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808012567/lh2623Isup2.hkl

e-64-o1012-Isup2.hkl^{(246.6KB, hkl)}

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

supplementary crystallographic information

Comment

Carbohydrates provide excellent starting materials for the synthesis of small chiral molecules (Collins & Ferrier, 1995). They are relatively inexpensive and provide an almost boundless pool of chiral building blocks (Draths et al., 1992). Much of their synthetic utility is however dependent on developing successful protecting group strategies.

Diazodiphenylmethane has been found to be a useful protecting group in the synthesis of methyl 2,3,6-tri-O-methyl-α-D-glucopyranoside and kojibiose octa-acetate (Jackson et al., 1982); monoalkylations of vicinal diols have been achieved with this reagent and other diaryldiazoalkanes with high regioselectivities (Petursson & Webber, 1982; Petursson et al., 2007; Petursson, 2003; Petursson, 2001). This is of particular interest for the protection of base sensitive sugar lactones as the reaction is carried out under neutral conditions (Best et al. 2008; Jenkinson et al. 2008).

The utility of the benzhydryl group as a protecting group in carbohydrate chemistry has here been demonstrated with the reaction of 3,5-O-benzylidene-D-xylono-1,4-lactone 1 with diphenyldiazomethane (Fig. 1). No epimerization at C2 was observed (Fig. 2).

Unlike the analogously protected lyxono lactone (Jenkinson et al., 2008), the asymmetric unit of the isomeric xylono lactone contains two crystallographically distinct molecules which are related by a pseudo 2-fold axis of symmetry. These are similar in geometry with the exception of two of the phenyl rings which sit at approximately 90° to each other (Fig. 3). When the core 20 atoms, of the carbohydrate backbone and 1 phenyl group, are mapped there is good overlap- r.m.s. deviations: posn 0.1139 Å, bond 0.0104 Å, torsion 2.5205°.

The crystal packing shows alternating layers of molecules in the ac plane (Fig. 4). The 5-ring lactones adopt envelope conformations with C2 or C102 out of the plane. The 6-ring ketals adopt chair conformations. There is no classic hydrogen-bonding.

Experimental

The title lactone was recrystallized from a 1:1 mixture of ethyl acetate and cyclohexane: m.p. 395–397 K; [α]_D²³ +129.1 (c, 1.02 in CHCl₃).