O[CH2:2][CH2:3][CH2:4][C:5]1[C:6](=[O:12])[NH:7][NH:8][C:9](=[O:11])[CH:10]=1.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.N(C(OC(C)C)=O)=NC(OC(C)C)=O>C1COCC1>[N:7]1[NH:8][C:9](=[O:11])[CH:10]=[C:5]2[CH2:4][CH2:3][CH2:2][O:12][C:6]=12A suspension of 4-(3-hydroxypropyl)-1,2-dihydro-3,6-pyridazinedione (1.48 g, 8.7 mmol) in THF (105 ml) was held in an ultrasound bath for 5 minutes, then cooled under argon in an ice bath. Triphenylphosphine (3.67 g, 14 mmol) was added, followed by diisopropyl azodicarboxylate (2.76 ml, 14 mmol). After 30 minutes the solvent was evaporated and the residue kept under high vacuum overnight. Chromatography, eluting first with 2.5% methanol/dichloromethane until triphenylphosphine oxide was removed and then with 5% methanol/dichloromethane, gave the product as an off-white solid (1.049 g, 79%).
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