Under carefully controlled conditions, the reaction of L-cysteine with 1, 4-benzoquinone leads to a mixture of 1, 4-benzothiazine oligomers, arising by decarboxylation and subsequent polymerization of the cyclic quinonimine 1, previously reported as the reaction product. When the reaction was stopped in the early stages by addition of sodium borohydride, work up of the mixture gave, besides the reduced dimer 11, the ...
![7-hydroxy-3,4-dihydro-2H-benzo[b][1,4]thiazine-3-carboxylic acid结构式](https://image.chemsrc.com/caspic/152/121637-98-7.png)