A solution (0.1 M) of methyl 6-cyclohexyl-5-phenyl-4H-thieno[3,2-b]pyrrole-2-carboxylate in THF at 0° C. was treated with NaH (4 eq., 60% dispersion in mineral oil), and the suspension was stirred at RT for 30 min then it was treated dimethyl sulfate (3 eq.). The mixture was stirred at RT for 2 h then it was quenched with water and extracted with AcOEt. The combined organic phase was washed with aqueous NaHCO3 (saturated solution) then dried. Evaporation of the solvent gave a residue that was dissolved in MeOH. The resulting solution (0.13 M) was treated with aqueous NaOH (2 N solution, 8 eq.) then the mixture was heated to reflux for 2 h. After cooling down, the mixture was concentrated and the residue was purified by RP-HPLC (Conditions: Waters X-TERRA MS C18, 5 micron, 19×150 mm; flow: 18 mL/min; Gradient: A: H2O+0.05% TFA; B: MeCN+0.05% TFA; 95% A linear to 90% A in 2 min, linear to 60% A in 2 min, linear to 40% in 2 min, linear to 30% A in 2 min, linear to 0% A in 2 min) to afford the title compound (42%) as a solid.
