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

Participants

Reaction Steps

N-(t-butylaminocarbonyl)-β-phenyl isoserine methyl ester (PREPARATION 1, 68 mg, 0.23 mM) is dissolved in dry THF (5 mL) and the solution treated with 2,4-dimethoxy benzaldehyde dimethyl acetal (70 mg, 0.33 mM) and pyridinium p-toluenesulfonate (6 mg, 0.02 mM) and the mixture warmed to reflux. Approximately 2 mL solvent is boiled away 3 times in a 45 minute period replenishing with 2 mL of fresh THF at which time TLC shows no starting material. The solvent is concentrated under reduced pressure and chromatographed (7 g of silica gel packed in ethyl acetate/1hexane, 1/3; elution with 80 mL ethyl acetate/hexane, 1/3; 45 mL ethyl acetate/hexane, 1/2; 30 mL ethyl acetate/hexane, 2/3 and 30 mL ethyl acetate/hexane, 1/1) to give the title compound: less polar isomer found in fractions 21-31--NMR (CDCl3, TMS) 1.19, 3.82, 3.85, 3.89, 4.68, 4.88, 5.52, 6.46, 6.70 and 7.25-7.50 δ, MS (FAB-High Res.) theory for C24H31N2O6 +H=443.2182, found=443.2172; more polar isomer in fractions 33-42--NMR (CDCl3, TMS) 0.99, 3.53, 3.81, 3.88, 4.05, 4.55, 5.45, 6.48, 6.79 and 7.25-7.50 δ; MS (FAB-High Res.) theory for C24H31N2O6 +H=443.2182, found=443.2180.

Provenance & Evidence