1,4-Dioxane → (2R,3S,5R,6R) 2-Carbamoyloxymethyl-2-methyl-6-(2-phenoxyacetamido)penam-3-carboxylic Acid p-Nitrobenzyl Ester

Participants

Reaction Steps

A solution of (1S,3S,5R,6R) 2,2-dimethyl-6-phenoxyacetamidopenam-3-carboxylic acid-1-oxide p-nitrobenzyl ester (7.52 g, 15.0 mmol) and trichloroacetyl isocyanate (5.0 ml, 7.9 g, 42 mmol) in dioxane (75 ml) was refluxed under nitrogen for 3.5 hours and concentrated in vacuo. The concentrate was stirred with methanol (100 ml) and the solution was decanted from a black tar with methanol rinses (2×10 ml). The solution was diluted with water (5 ml), adjusted to pH 7.4 with 5% sodium bicarbonate, and held at pH 7.4-7.5 with 3% H2SO4 for 2.5 hours. The mixture was distributed between methylene chloride (100 ml) and water (50 ml). The organic phase was washed with water (50 ml), combined with a CH2Cl2 back extract (50 ml), dried (4A molecular sieve), polish filtered with CH2Cl2 washes (2×20 ml), and concentrated in vacuo to a light brown oil.

Provenance & Evidence