A solution of tolanoic-Thr methyl ester (4) (2.34 g, 7.0 mmol) in MeOH (20 ml) and DCM (30 ml) was added to a cooled (−10° C. bath) suspension of hydroxylamine HCl salt (4.81 g, 70.0 mmol) and NaOMe (4.16 g, 77.0 mmol) in MeOH (30 ml). Follow reaction by LCMS. After stirring for 2 hours, the reaction seems to stall at 50% completion. Add an additional 1 equivalent of NaOMe (0.416 g). After 3 hours, the reaction was 75% complete. Add an additional 0.5 equivalent of NaOMe (0.21 g). After 4 hours, the reaction was 90% complete. Add an additional 0.15 equivalent of NaOMe (0.064 g) for a total of 12.65 equivalents of NaOMe. The pH of the reaction was between 11-12 and had reacted about 95% completion. The reaction was diluted with EtOAc (500 ml) and washed with sat. aq. NaHCO3 (2×60 ml), 50% diluted brine (60 ml), sat. brine (60 ml), dried with Na2SO4, filtered and concentrated under reduced pressure. The residue was dissolved in minimal DMA. The product was purified by prep. HPLC using a reverse phase Ultro 120 C18 column running a 2% gradient (AcCN/water, 0.1% TFA). The purified fractions were lyophilized to dryness. The product as the TFA salt was dissolved in AcCN/water (50:50) (80 ml), 1N aq. HCl (13 equivalent) and lyophilized again to give 1.3 g of white powder in 55% yield and >97% purity.
