Cyclopropanecarbonyl chloride (0.014 ml) was added to a solution of Intermediate 18 (0.54 g) and N,N-diisopropylethylamine (0.063 ml) in dichloromethane (2 ml). The solution was stirred for 3 h at 23° C. The solvent was removed in vacuo and the residue purified by solid phase extraction (Isolute SCX sulphonic acid column) eluting with methanol followed by 10% 0.880 ammonia solution in methanol. The basic fraction was concentrated in vacuo and the residue was further purified using a silica gel solid phase extraction cartridge (1 g Varian Bond Elut) eluting with 0–1% methanol in ethyl acetate, to give the title compound as a clear gum (0.023 g).
