Synthesis of homochiral amino acid pyrazine and pyrrole analogues of glutamate antagonists

Use of the acid 7 and the aldehydes 23a and 23b in “ring switching” reactions with hydrazines has given β-(1-aminopyrrole)amino acids as kinetic products. The products from the reaction of the aldehyde have been converted into β-(pyrazine)amino acids by an equilibration–dehydration sequence. A variety of homochiral reduced heterocyclic amino acids containing two chiral centres has been prepared in this way. Some of the product amino acids undergo “reverse ring switching” to the corresponding pyroglutamic acid derivatives. © 2002 The Royal Society of Chemistry.