[NH2:1][C:2]1[C:11]([C:12]([O:14]C)=[O:13])=[C:10]2[C:5]([CH:6]3[CH2:16][CH:7]3[CH2:8][O:9]2)=[CH:4][CH:3]=1.O.[OH-].[Li+]>O1CCOCC1.O>[NH2:1][C:2]1[C:11]([C:12]([OH:14])=[O:13])=[C:10]2[C:5]([CH:6]3[CH2:16][CH:7]3[CH2:8][O:9]2)=[CH:4][CH:3]=1A mixture of methyl (1aRS,7bSR)-5-amino-1,1a,2,7b-tetrahydrocyclopropa[c]chromene-4-carboxylate (Intermediate 42, 1.0 g) and lithium hydroxide monohydrate (0.96 g) in dioxane (16 mL) and water (14 mL) was stirred and heated at 90° C. for 1 hour. After cooling, the mixture was concentrated under vacuum and the residue was diluted with water and neutralised to pH7 with formic acid. The mixture was then extracted with ethyl acetate, dried (Na2SO4) and filtered and the filtrate was evaporated to dryness to give (1aRS,7bSR)-5-amino-1,1a,2,7b-tetrahydro-cyclopropa-[c]chromene-4-carboxylic acid (0.97 g) as a yellow oil.
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