Under N2 was charged the product of step (vi) above (175.5 g, 0.324 mol), the product of step (x) above (145.0 g, 0.369 mmol) and iPrOAc (8800 mL). The resulting solution was heated to 60° C. and NEt3 (9.3 mL) was charged in one portion, then the mixture was left to stir at 60° C. overnight, following which HPLC analysis indicated 25.77% product of step (vi), 3.60% product of step (x) and 57.85% product of step (xi). Further product of step (x) (36.0 g, 0.092 mol) was charged, then the reaction was left to stir at 60° C. overnight, whereupon HPLC analysis indicated 5.47% product of step (vi), 3.72% product of step (x) and 73.33% product of step (xi). The reaction mixture was cooled to room temperature, before being concentrated to isolate a dark purple solid (522.9 g). This solid was recrystallised from acetonitrile (2615 mL, 5 volumes), before being collected via vacuum filtration and washed with iPrOAc (2×500 mL). The pink solid obtained was dried, under vacuum, at 40° C. overnight, yielding 181.1 g (66.5%) of the title compound with HPLC purity 99.27%. 1H NMR conformed to structure.
