Methyl trans-4-bromo-2-butenoate (Methyl 4-bromocrotonate) was used in the synthesis of highly substituted benzoxepines or benzopyrans and L-α-amino [4,5-3H]adipic acid. Methyl trans-4-bromo-2-butenoate (Methyl 4-bromocrotonate) was used in the synthesis of highly substituted benzoxepines or benzopyrans and L-α-amino [4,5-3H]adipic acid.