4 μl (56 μmol) of methanesulphonyl chloride were added to a solution of 30 mg (51 μmol) of the compound of Example 58A in 0.5 ml of pyridine, and the mixture was stirred at RT overnight. Since HPLC analysis showed a lot of remaining starting material, further equivalents of methane-sulphonyl chloride (3.1 eq. in total) were added a little at a time until complete conversion had been achieved. 100 μl each of water and methanol were then added. After 5 min of stirring, the reaction mixture was diluted with about 3 ml of DMSO and separated by preparative HPLC [Method 8]. The product-containing fraction was freed from the solvent on a rotary evaporator and the residue was dried under high vacuum. This gave 22 mg (68% of theory) of the title compound.
