Sodium Bicarbonate → Cephalothin

Participants

Reaction Steps

A suspension of p-methoxybenzyl dl-3-acetoxymethyl-7β-(2-thienylacetamido)-3-cephem-4-carboxylate (13.8 mg., 0.027 mMol) in anisole (70 μl.) is cooled in an ice-bath. Ice-cold trifluoroacetic acid (350 μl.) is added and the mixture is swirled to make it homogeneous. The resulting solution is kept at 0°C. for 5 minutes, then evaporated in vacuo at 0°C. to remove excess trifluoroacetic acid. The oily residue is allowed to warm to room temperature under vacuum, then diluted with anisole (0.5 ml.) and evaporated in vacuo at 35°C. The resulting semi-solid is taken up in water (5 ml.) containing sodium bicarbonate (23 mg., 0.27 mMol) and the solution is extracted with methylene chloride (3 × 2 ml.). The aqueous phase (pH 8.65) is acidified to pH 2.6 with 1 M pH 2 phosphate and is extracted with ethyl acetate (4 × 3 ml.). The combined extracts are dried over magnesium sulfate, filtered, and evaporated in vacuo to yield dl-3-acetoxymethyl-7β-(2-thienylacetamido)-3-cephem-4-carboxylic acid (10.1 mg.) as a white solid: ir (neat) 2.8-4.5, 5.60, 5.76, 5.91, 6.50, 7.23, 8.10 and 9.63μ; nmr (Me2CO-d6) τ 7.96 (s, 3, CH3CO), 6.58, 6.20 (dd, 2, J=19Hz, 2-CH2), 6.08 (s, 2, ArCH2), 5.20, 4.83 (dd, 2, J=13Hz, CH2OAc), 4.86 (d, 1, J=4.5Hz, H6), 4.13 (d of d, 1, J=4.5Hz and J-9Hz. H7), 2.85 (m, 3, ArH), and 1.96 (d, 1, J=9Hz, NH).

Provenance & Evidence