Benzenesulfonic acid, 4-methyl-, compd. with pyridine (1:1) → (4S,5R)-N-Carbobenzyloxy-2-(2,4-dimethoxyphenyl)-4-phenyl-5-oxazolidinecarboxylic acid methyl ester

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Reaction Steps

N-Carbobenzyloxy-β-phenyl isoserine methyl ester (Preparation No. 19, 3C, 0.375 g, 1.14 mM) is dissolved in dry THF (10 mL) and the solution treated with 2,4-dimethoxy benzaldehyde dimethyl acetal (4, 0.300 g, 1.42 mM) and pyridinium p-toluenesulfonate (10 mg) and the solution heated to distill off the THF and methanol. After ½ the THF is distilled off, THF (10 mL) is added and the reaction distilled to ½ volume again. The process is repeated three times. The reaction is then concentrated in vacuo and the residue chromatographed over 75 g silica gel packed and eluted in acetone-hexane (300 mL of 20-80 and 300 mL of 25-75). Fractions of 20 mL are collected and analyzed by TLC. The following fractions are combined and evaporated under vacuum.

Provenance & Evidence