Six-Membered Rings with Three Heteroatoms

4-Triazines are formed from AAs after being transformed with DMF-DMA into amidines and subsequent treatment with hydrazine [90H(30)393]. Esters of heterocyclic dehydroamino acids reacted in a similar 

Ethyl sulfonamidomethylglycinate was prepared from L-cystine in several steps it was then transformed with l,l -carbonyldiimidazole into thiadia-zine derivative 51 (84JMC228). 

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