反应详情

A suspension of 2.2 g of methylene-(2S,5R)-3,3-dimethyl-6-(3-methyl-2-oxobutylidene)-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate pivalate in 300 ml of dimethyl sulphoxide and 500 ml of phosphate buffer (pH 7.1) is treated at 20° with 2 ml of a suspension of pig liver esterase (3 mg/ml). The reaction mixture is stirred at 20° for 2 hours and subsequently extracted with ether. The aqueous phase is acidified (pH 3.2) with 50% citric acid and extracted with ether. The organic extract is washed with distilled water, dried over magnesium sulphate, filtered and evaporated. There is obtained an oily residue which is dissolved in 200 ml of ether and treated with 2.4 ml of a 2M solution of sodium 2-ethylcaproate. The crystalline precipitate is filtered off under suction, washed with ether and dried over phosphorus pentoxide in vacuo. There is obtained sodium (2S,5R)-3,3-dimethyl-6-(3-methyl-2 -oxobutylidene)-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate of melting point 145° (decomposition). [Rf : 0.41; chloroform/ethyl acetate/acetic acid (5:4:1); NMR (D2O) δ (ppm); 1.17 (6H); 1.53 (3H); 1.61 (3H); 2.95 (1H); 4.4 (1H); 6.05 (1H); 6.9 (1H)].

1. extractionsubsequently extracted with ether
2. extractionextracted with ether
3. extractionThe organic extract
4. washis washed with distilled water
5. dry with materialdried over magnesium sulphate
6. filtrationfiltered
7. customevaporated
8. customThere is obtained an oily residue which
9. filtrationThe crystalline precipitate is filtered off under suction
10. washwashed with ether
11. dry with materialdried over phosphorus pentoxide in vacuo