反应详情

To a flame dried flask under an inert atmosphere containing potassium tert-butoxide (12.18 g, 108.58 mmol) and water (900 mg, 50.00 mmol) at 0° C. is added (+/-)-tetrahydro-3-oxo-3 H-oxazolo(3,4-a)pyrazin-7(1 H)-carboxylic acid phenylmethylester (Step 3, 10.00 g, 36.19 mmol). The reaction is warmed to ambient temperature, stirred for 2 hours, cooled to 0° C., acidified to pH=2 with conc. HCl, adjusted to pH=9 with 1N NaOH, and extracted with methylene chloride (2×100 mL). The organic extracts are combined, dried over Na2SO4, concentrated in vacuo, and chromatographed on silica gel (230-400 mesh, 250 mL), eluting with chloroform/methanol (95/5). The appropriate fractions are combined (Rf =0.13, TLC, chloroform/methanol, 90/10) and concentrated in vacuo to give the title compound, NMR (CDCl3) 7.34-7.25, 5.09, 3.95, 3.55-3.53, 3.41, 3.34, 2.92, 2.72-2.70.

1. customTo a flame dried flask under an inert atmosphere
2. temperaturecooled to 0° C.
3. extractionextracted with methylene chloride (2×100 mL)
4. dry with materialdried over Na2SO4
5. concentrationconcentrated in vacuo
6. customchromatographed on silica gel (230-400 mesh, 250 mL)
7. washeluting with chloroform/methanol (95/5)
8. concentrationconcentrated in vacuo