Phosphate → 2,2-Dimethyl-3alpha-cyanopenam

関与物質

反応手順

Activated mossy zinc (500 mg) and zinc dust (100 mg) are added to a solution of 2,2-dimethyl-3α-cyano-6α-bromopenam (522 mg, 2 mmol) and p-(2-tetrahydropyranyloxy)benzaldehyde (750 mg, 3.75 mmol) prepared according to E. Piers, W. deWaal and R. W. Britton, J. Am. Chem. Soc., 93, 5113 (1971) in 1 ml of dry tetrahydrofuran. After stirring vigorously at 50° for 3 hrs., the mixture is allowed to cool and 1 ml of pH 5 phosphate buffer is added. After standing for 10 min., the solids are removed by filtration and washed thoroughly with ethyl acetate. The filtrate is extracted with ethyl acetate. The combined extracts are washed with phosphate buffer and saturated sodium chloride, dried with sodium sulfate and the solvents removed by evaporation. The crude material is purified by chromatography on 60 g of silica gel using 40% acetone/chloroform as eluant to afford 2,2-dimethyl-3α-cyanopenam as a by-product melting at 73°- 75° C. and a mixture of 2,2-dimethyl-3α-cyano-6α-[p-(2-tetrahydropyranyloxy)-α-hydroxybenzyl]penam and 2,2-dimethyl-3α-cyano-6β-[p-(2-tetrahydropyranyloxy)-α-hydroxybenzy]-penam. Separation of the 6α-and 6β-compounds is effected by PLC (10% acetone/toluene; two developments) providing the individual 6α- and 6β-compounds.

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