反应详情

A solution of (1S,3S,5R,6R) 2,2-dimethyl-6-phenylacetamidopenam-3-carboxylic acid-1-oxide p-nitrobenzyl ester (4.85 g, 10.0 mmol) and acetyl isocyanate (2.3 ml, 30 mmol) in dioxane (50 ml) was refluxed under nitrogen for 7 hours. The light orange solution was concentrated in vacuo to a foam which was chromatographed on silica gel (500 g) with methylene chloride:acetone; 9:1, v:v. Two major bands were eluted; the first was the Δ3 3-methylcephem (28%, 1.29 g) and the second was the title compound obtained in 45% yield (2.56 g) as an off-white foam: mp 83°-85°; nmr 100 MHz (CDCl3) ppm 8.24 (2, d, J=9 Hz, 1/2 aromatic AB pNB), 7.61 (2, d, J=9, 1/2 pNB AB), 7.28 (5, s, phenyl), 5.54 (2, m's C6 --C5 --H's), 5.40 (2, br s, pNB methylene), 4.91 (1, s, C3 --H), 4.27 1, d, J=12, 1/2 C2 --CHHO AB), 4.08 (1, d, J=12, 1/2 C2 -methylene AB), 3.12 (2, s, ##STR72## 2.12 (3, s, acetyl), and 1.41 (3, s, C2 --CH3).

1. concentrationThe light orange solution was concentrated in vacuo to a foam which
2. customwas chromatographed on silica gel (500 g) with methylene chloride
3. washTwo major bands were eluted
4. customobtained in 45% yield (2.56 g) as an off-white foam