| 摘要 |
1-[ alpha -(Carboxy)-4-hydroxybenzyl]-3 beta -aminoazetidin-2-one esters are prepared by converting 2-acyl-3,3-dialkyl-7-oxo- alpha -[4-(benzyloxy)phenyl]-4-thia-2,6-diazabicyclo[3.2.0]heptane-6-acetic acid esters with mercuric acetate in an aqueous organic solvent mixture, e.g., in aqueous methanol, to 7-oxo-3-phenyl- alpha -[4-(benzyloxy)phenyl]-4-oxa-2,6-diazabicyclo[3.2.0]hept-2-ene-1-acetic acid esters and the latter are reacted with PCl5 and pyridine to provide the monocyclic 1-[ alpha -(carboxy)-4-benzyloxybenzyl]-3 beta -( alpha -chlorobenzylideneamino)-4-chloroazetidin-2-one esters. Reduction of the dichloro azetidin-2-one with an organo tin hydride and azobisisobutyronitrile affords the deschloro, 1-[ alpha -(carboxy)-4-benzyloxybenzyl]-3 beta -benzylideneaminoazetidin-2-one ester. The latter is hydrolyzed and the benzyloxy group is cleaved via catalytic hydrogenolysis to yield an ester of 1-[ alpha -(carboxy)-4-hydroxybenzyl]-3 beta -aminoazetidin-2-one. The 3 beta -amino ester is useful for the preparation of the antibiotic FR 1923 (nocardicin).
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