3) in the construction of tetronic and tetramic acidsfrom various carboxylic acid derivatives is demonstrated by new reactions and extensions of known ones. With α-hydroxy or α-amino esters, 3 affords tetronates or tetramates. A two-step synthesis of (-)-epi-blastmycinolactol shows that allyl α-hydroxy esters can be domino Wittig-Claisen reacted to give 3-allyltetronic acids. More extended Wittig-Claisen-Conia