To a solution of acetaldehyde (0.041 ml from a stock solution made up from 0.0127 l acetaldehyde dissolved in 1 ml DCM)) in dry DCM (0.4 ml) treated with acetic acid (0.1 ml from a stock solution made up from 0.0054 ml acetic acid dissolved in 1 ml DCM) was added N-{(3S)-1-[(1S)-2-(3-aminopiperidin-1-yl)-1-methyl-2-oxoethyl]-2-oxopyrrolidin-3-yl }-6-chloronaphthalene-2-sulfonamide [Example 365] (0.045 g) followed by tetraethylammonium triacetoxyborohydride (0.005 g). The mixture was stirred at room temperature, under nitrogen, for 60 h. DCM (1 ml) was added and the resultant solution washed with saturated sodium bicarbonate (1 ml) in a hydrophobic frit. The solvent was concentrated under reduced pressure and the residue purified by mass directed preparative h.p.l.c. to give the title compound (0.8 mg) as an oil.
