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A mixture of 2-(8-phenyl-1,4-dioxa-spiro[4.5]dec-8-yl)-acetamidine acetic acid salt (268) (500 mg, 1.5 mmol) and 2-benzyloxy-3-hydroxy-but-2-enedioic acid 4-tert-butyl ester 1-methyl ester (4) (553 mg, 1.8 mmol) in methanol (15 mL) were cooled to 0° C., followed by the addition of NaOMe (25% in methanol) (1 mL, 4.5 mmol) and the reaction mixture was stirred at room temperature for 16 h while silica thin layer chromatography was performed (ethyl acetate:hexane=7:3, Rf=0.6). The reaction mixture was diluted with ethyl acetate (40 ml) and washed with brine (2×20 mL). the reaction mixture was subsequently dried and concentrated in vacuo to get a crude mixture which was purified by normal silica gel (100-200 mesh) column chromatography using an eluent gradient (30-50% ethyl acetate in hexane) to obtain pure 5-benzyloxy-6-hydroxy-2-(8-phenyl-1,4-dioxa-spiro[4.5]dec-8-ylmethyl)-pyrimidine-4-carboxylic acid tert-butyl ester (269) (590 mg, 74.09%) as a brown sticky mass.

1. washwashed with brine (2×20 mL)
2. customthe reaction mixture was subsequently dried
3. concentrationconcentrated in vacuo
4. customto get a crude mixture which
5. customwas purified by normal silica gel (100-200 mesh) column chromatography