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. 2015 Jan 28;2(1):140160. doi: 10.1098/rsos.140160

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© 2015 The Authors.

© 2015 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.

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Figure 4. — CR and CS react reversibly with N-acetyl-l-cysteine methyl ester in CDCl₃. (a) Equilibria and product diastereomers. (b) ¹H COSY (left) and ¹H-¹³C HSQC with DEPT-135 editing (right) NMR spectra: the CH₂ group of the diastereomers gives a negative signal. (c) ¹H-¹³C HMBC NMR spectrum showing signals for the two diastereomers. (d) ¹H NMR spectra of mixtures of 2- (CS), 3- and 4-Cl analogues with the cysteine ester. The substituent has a strong electronic effect on the coupling pattern of the protons of the SCHCH(CN)₂ group of the product (marked with asterisks). A Cl atom in the 2-position produces symmetrical doublets for both diastereomers. A Cl atom in the 3-position causes these signals to overlap, but gives an integral of 3:1 consistent with the proposed structures. A Cl atom in the 4-position produces four doublets, but due to their similarity, roofing effects are observed. These types of coupling patterns were seen across all the substituents and positions studied.