On the other hand, DP5 showed m/z diagnostic MS2 m/z ions at 282.0872 and 253.0280 indicating the loss of -SO2 and C5H3NO fragments suggesting the hydroxylation of the pyridinyl ring. Finally, DP8 presented m/z fragment ions at 226.0171 and 162.0565 (loss of -C6H4N2O and -C6H4N2-SO2...