Methyl (1aRS,7bSR)-5-[2-((Z)-3-diethylaminoprop-1-enyl)-4-fluorobenzenesulfonylamino]-1,1a,2,7b-tetrahydrocyclopropa[c]chromene-4-carboxylate (Intermediate 40, 0.185 g) and lithium hydroxide monohydrate (0.159 g) were suspended in dioxane (4 mL) and water (1 mL). The reaction mixture was irradiated in the microwave at 135° C. for 30 minutes. After cooling, the mixture was acidified to pH4 with formic acid, then ethanol and toluene were added and the mixture concentrated in vacuo. The residue was triturated with a mixture of methanol and DCM (10%) and the solid was filtered off and washed with a mixture of methanol and DCM. The filtrate was concentrated in vacuo and the residue was purified by chromatography on silica, eluting with a mixture of methanol and DCM with a gradient of 0-8%. The resultant product was triturated with ethyl acetate and dried in vacuo at 50° C. to give (1aRS,7bSR)-5-[2-((Z)-3-diethylaminoprop-1-enyl)-4-fluorobenzenesulfonylamino]-1,1a,2,7b-tetrahydrocyclopropa[c]chromene-4-carboxylic acid (0.066 g) as a white solid.
