Chemistry is the experimental and theoretical study of materials on their properties at both the macroscopic and microscopic levels. 52-90-4, Name is L-Cysteine, molecular formula is C3H7NO2S. In an article, author is Depciuch, Joanna,once mentioned of 52-90-4, Quality Control of L-Cysteine.
The cyclic trimerization of substituted 4-alkylaminobenzoic acids was investigated. From NMR analyses of DiMeO_C3A with two methoxy groups, which was obtained by using SiCl4 as a dehydrative condensation reagent and purified by preparative GPC, a syn/anti ratio of 60/40 was obtained. On the other hand, 3Br_C3A with one bromine group at the ortho-position relative to the amide nitrogen was synthesized by using PPh3/Cl3CCCl3 as a dehydrative condensation reagent and isolated by SiO2 column chromatography. 3Br_C3A showed an inverse stereoselectivity, namely, a syn/anti ratio of 25/75 was calculated based on the comprehensive NMR analyses. The population of stereoisomers had no relationship with the dehydrative condensation reagent and reaction temperature. The solvent character also had a negligible influence on the syn/anti ratio in solution reflecting the rigid structure of 3Br_C3A.
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Reference:
Amide – Wikipedia,
,Amide – an overview | ScienceDirect Topics