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