AN UNUSUAL STEREOSELECTIVE DECARBOXYLATION - A KEY REACTION TO AN IMPORTANT INTERMEDIATE FOR CARBAPENEM ANTIBIOTICS

The dramatic difference in reactivity of the two diastereomeric acid e sters 4A and 4B during decarboxylation has been thoroughly investigate d, The (R) isomer 4A underwent decarboxylation to provide a 94:6 mixtu re of 5A and 5B at 80 degrees C in 5-6 h. Under the same conditions th e (S) isomer 4B did not undergo decarboxylation and with further heati ng to 120 degrees C gave mainly the ring-opened decomposition product 6 along with unidentified decomposition products, A mechanistic ration ale for this unusual reactivity profile is provided.