FC(F)(F)C(O)=O.C(OC([NH:15][C:16]1[C:25]([C:26]([O:28][CH3:29])=[O:27])=[C:24]2[C:19]([C:20]3([CH3:31])[CH2:30][CH:21]3[CH2:22][O:23]2)=[CH:18][CH:17]=1)=O)(C)(C)C>ClCCl>[NH2:15][C:16]1[C:25]([C:26]([O:28][CH3:29])=[O:27])=[C:24]2[C:19]([C:20]3([CH3:31])[CH2:30][CH:21]3[CH2:22][O:23]2)=[CH:18][CH:17]=1Trifluoroacetic acid (4 mL) was added to a solution of methyl (1aRS,7bSR)-5-(tert-butoxycarbonylamino)-7b-methyl-1,1a,2,7b-tetrahydrocyclopropa-[c]chromene-4-carboxylate (Intermediate 51, 0.6 g) in dichloromethane (4 mL) and the resultant dark solution was stirred at room temperature for 1 hour. The solution was evaporated to dryness and the residue was partitioned between water and ethyl acetate and treated with a small amount of solid sodium bicarbonate until the pH of the aqueous layer was >7. The layers were separated and the aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with water, dried (MgSO4) and filtered. The filtrate was evaporated to dryness to give methyl (1aRS,7bSR)-5-amino-7b-methyl-1,1a,2,7b-tetrahydrocyclopropa-[c]chromene-4-carboxylate (0.402 g) as a red/orange solid.
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