Compound ribo-1

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Compound data: CIF

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

Synthesised in the reaction between 2-aminooxazole 4 and aminal 8b as a mixture of diasteroisomeric pentose aminooxazolines as outlined in 1.

Crystallisation of ribo-1 from precipitate C (Supplementary Scheme 4, green). A single crystal of ribo-1 (precipitate C, Supplementary Scheme 4, green) was found to be homochiral D-ribo-1 by single crystal X-ray diffraction. The bulk sample of ribo-1 crystals were analysed by chiral HPLC (following the procedure as described above (Determination of enantiomeric ratio of ribo-1); bulk ribo-1 was found to be racemic, indicating that ribo-1 (precipitate C) had crystallised as conglomerate crystals from racemic aminal 8b (precipitate B). (Single crystal X-ray structure for D-ribo-1, CCD 1477052; Supplementary Figure 165).

Crystallisation of ribo-1 from aminal 8b: 2-Aminooxazole (4; 42 mg, 0.5 mmol) was added to a suspension of aminal 8b (prepared from rac-glyceraldehyde (2b; 126 mg, 0.5 mmol) and 2-aminothiazole (7; 100 mg, 1.0 mmol) in sodium phosphate buffer (pH 7, 1 mL) and stirred at 40 °C for 24 h. The resultant homogenous solution was then incubated at 4 °C, leading to the formation of crystalline precipitate. The supernatant was removed and the crystals washed with ice-cold water and dried under vacuum. A sample of the crystalline material (4 mg) was dissolved in D₂O (1 mL) and ¹H NMR spectra were acquired, the data matched that of ribo-1. A crystal of ribo-1 was analysed by single crystal X-ray diffraction and found to be rac-ribo-1 (rac-ribo-1ⁱ) and as an enantiomorphously twinned crystal. Chiral HPLC analysis was carried out on the bulk ribo-1 crystalline material (following the procedure as described in Determination of enantiomeric ratio of ribo-1); ribo-1 was found to be racemic by chiral HPLC, indicating that ribo-1 had crystallised as enantiomorphously twinned crystals from aminal 8b. (Single crystal X-ray structure for rac-ribo-1ⁱ_, CCD 1477049, Supplementary Figure 162).

Crystallisation of ribo-1 from ribose: D-, L- or rac-Ribose (50 mg, 0.33 mmol) and cyanamide (3; 14 mg, 0.33 mmol) were dissolved in NaHCO₃/Na₂CO₃ buffer at pH 9.4 (0.33M) and incubated at room temperature. Large crystals were observed to form after 24 h. The supernatant was removed and the crystals washed with ice-cold water and dried under vacuum. A sample of the crystalline material (5 mg) was dissolved in D₂O (1 mL) and ¹H NMR spectra were acquired, the data matched that of ribo-1. A crystal of ribo-1 was analysed by single crystal X-ray diffraction and found to be L-ribo-1 (from L-ribose), and rac-ribo-1 (from D,L-ribose). Chiral HPLC analysis was carried out on the bulk ribo-1 crystalline material (following the procedure as described in Determination of enantiomeric ratio of ribo-1); ribo-1 was found to be D-ribo-1 (from D-ribose), L-ribo-1 (from L-ribose), and rac-ribo-1 (rac-ribo-1ⁱⁱ, from rac-ribose). (Single crystal X-ray structure for L-ribo-1_, CCD 1477053, Supplementary Figure 166; single crystal X-ray structure for rac-ribo-1ⁱⁱ_, CCD 1477055, Supplementary Figure 163).

Crystallisation of ribo-1 from rac-glyceraldehyde (2b): to a stirred solution of rac-glyceraldehyde (2b; 90 mg, 1 mmol) in H₂O (1 mL) was added 2-aminooxazole (4; 84 mg, 1 mmol). The solution was adjusted to pH 6.5 with 4M HCl/NaOH and incubated at room temperature. Bundles of needle-like crystals formed after 24 h. The supernatant was removed and the crystals washed with ice-cold water and dried under vacuum. A sample of the crystalline material (5 mg) was dissolved in D₂O (1 mL) and ¹H NMR spectra were acquired, the data matched that of ribo-1. A crystal of ribo-1 was analysed by single crystal X-ray diffraction and found to be rac-ribo -1ⁱⁱⁱ and as an enantiomorphously twinned crystal. Chiral HPLC analysis was carried out on the bulk ribo-1 crystalline material (following the procedure as described in Determination of enantiomeric ratio of ribo-1); ribo-1 was found to be racemic by chiral HPLC, indicating that ribo-1 had crystallised as enantiomorphously twinned crystals from rac-glyceraldehyde (2b). (Single crystal X-ray structure for rac-ribo -1ⁱⁱⁱ_, CCD 1477050, Supplementary Figure 164)