The product of step (b) above (500 mg) was treated with concentrated hydrochloric acid (0.8 ml) and water (0.8 ml) to form a paste. The paste was stirred at 0°-10° and a solution of sodium nitrite (105 mg) in water (0.5 ml) added dropwise. After stirring for 40 minutes the resultant solution was added slowly to pyridine (5 ml) stirred at 80°. The mixture was stirred for a further 40 minutes then concentrated in vacuo. The residue was slurried with 0.880 ammonia and the mixture again concentrated in vacuo. The residue was slurried with water and extracted with ethyl acetate. The ethyl acetate was washed with water and brine, then dried and evaporated to leave a brown gum. Flash chromatography produced the required product as a pale brown solid, MS MW 393 bp 216.
