[O:1]1[CH2:5][CH2:4]/[C:3](=[CH:6]/[C:7]([O:9][CH2:10][CH3:11])=[O:8])/[CH2:2]1.[NH3:12]>O1CCOCC1.CO>[NH2:12][C:3]1([CH2:6][C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH2:4][CH2:5][O:1][CH2:2]1Ethyl (2Z)-dihydrofuran-3(2H)-ylideneacetate (Preparation 36, 1.29 g, 8.25 mmol) was stirred in 1,4-dioxane (7 mL) in a microwave vial. A solution of 7M ammonia in methanol (5 mL) was added and the reaction heated for 4 hours at 150° C. in a Biotage Initiator™ microwave. The reaction was concentrated in vacuo, but later deemed not to have reached completion. A solution of 7M ammonia in methanol (7 mL) was added and the reaction heated again for 3 hours at 150° C. in the microwave. A further portion of 7M ammonia in methanol (3 mL) was added and the reaction heated for a further 2 hours. The reaction was concentrated in vacuo to afford the title compound along with the methyl ester where trans-esterification had occurred. The material was used without further purification in the next step.
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