Serendipitous oxidation product of BIBN4096BS: A potent CGRP receptor antagonist

An oxidation product (5) formed during the synthesis of BIBN-4096BS (1) was found to be a potent CGRP antagonist (IC50 = 0.11 nM). While 5 was found to be ten-fold less potent than 1, another analog 8 with lower molecular weight containing the oxidized fragment demonstrated twenty-fold higher activity than its parent 7. Alternative conditions which preclude the formation of the oxidation product are described. The activities of 1, 5, 7 and 8 in functional cAMP assay are also discussed.

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