反应详情

To a methylene chloride (CH2Cl2) solution (15 mL) containing betulin (2, 450 mg, 1.016 mmol) was added dihydropyran (DHP, 94 mg, 1.12 mmol) and pyridinium p-toluene sulfonate (PPTS, 30 mg. 0.12 mmol) at room temperature and under a nitrogen (N2) blanket. The resulting mixture was stirred for three days. After completion of the reaction, 5 mL of saturated sodium bicarbonate (NaHCO3) was added to the reaction mixture. The organic layer was separated from the aqueous layer, next was washed with a saturated sodium chloride (NaCl) solution (5 mL), then dried over MgSO4, filtered, and finally the methylene chloride was removed under vacuum. The residue was chromatographed over silica gel using petroleum ether/EtOAc (4:1 volume ratio) to provide the mono-THP ether of betulin, i.e., compound 4, as a diastereomeric mixture (508 mg, 95%). The diastereomeric mixture 4 was subjected to a subsequent reaction without separation and isolation of isomers. A mass spectrum of the reaction product gave MS (CI) m/e (rel intensity) 441 (-THP, 10), 425 (-OTHP, 100), 407 (-OTHP-H2O, 12).

1. additionwas added to the reaction mixture
2. customThe organic layer was separated from the aqueous layer
3. washnext was washed with a saturated sodium chloride (NaCl) solution (5 mL)
4. dry with materialdried over MgSO4
5. filtrationfiltered
6. customfinally the methylene chloride was removed under vacuum
7. customThe residue was chromatographed over silica gel