The mass spectral fragmentation of isoxazolyldihydropyridines

The mass spectral fragmentation of 4-isoxazolyl-1,4-dihydropyridines has been examined with the aid of linked metastable scanning. Three prominent pathways involve (i) O-N bond cleavage of the isoxazole followed by the loss of R²CN, (ii) loss of carboalkoxy from the 3- and/or 5- position of the dihydropyridine and, (iii) loss of the 4-isoxazolyl-substituent.