[O:1]1[CH2:6][CH2:5][CH2:4]/[C:3](=[CH:7]/[C:8]([O:10][CH2:11][CH3:12])=[O:9])/[CH2:2]1.[NH3:13]>O1CCOCC1.CO>[NH2:13][C:3]1([CH2:7][C:8]([O:10][CH2:11][CH3:12])=[O:9])[CH2:4][CH2:5][CH2:6][O:1][CH2:2]1Ethyl (2Z)-dihydro-2H-pyran-3(4H)-ylideneacetate (Preparation 37, 1.21 g, 7.11 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 3 hours at 150° C. in a Biotage Initiator™ microwave. A further solution of 7M ammonia in methanol (2 mL) was added and the reaction heated again for 2 hours at 150° C. in the microwave. The reaction was concentrated in vacuo and the residue dissolved in a further portion of 7M ammonia in methanol (10 mL) and heated for a further 5 hours at 150° C. in the microwave. 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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