5.3 g of the acid of Step A were dissolved in 66 ml of dichloromethane and then 46 ml of a solution of diphenyl diazomethane at 6.5 g in ether were added at 15° C. The mixture was stirred for 16 hours at ambient temperature and then water was added, followed by decanting and acidifying with acetic acid. Washing with a saturated solution of sodium bicarbonate, drying and evaporating the solvents yielded after chromatography on silica and eluting with an ethyl acetate—hexane mixture (50-50) 4.0 g of the desired product with a Rf=0.17.
