Hydrogen Bonding of Cysteine in the Solid Phase. Crystal and Molecular Structures of L-Cysteine Methyl Ester.HCl and L-Cysteine Ethyl Ester.HCl.

The solid-state molecular structure of the S-nitroso derivative of l-cysteine ethyl ester hydrochloride

“…3 We believe that the lower occupancy of the -S(1′)-N(2′)-O(3′) group (only 30%) probably compromises the accuracy of the determined metrical parameters for this minor component, hence we are hesitant to over-interpret these bond lengths and angles. The C(4)-C(5)-S(1) bond angle of 117.6(1)°, although it deviates from the ideal tetrahedral angle, is similar to the corresponding angles in L-cysteine (114.8(3)°; orthorhombic form) [42], Lcysteine ethyl ester hydrochloride (115.7(1)°) [53], and the cysteinyl group of glutathione (114.7(4)°) [54].…”

High-Field Chlorine NMR Spectroscopy of Solid Organic Hydrochloride Salts: A Sensitive Probe of Hydrogen Bonding Environment

“…29 Presented in Figure 7 is a summary of chlorine quadrupolar coupling constants as a function of the total number of N-H‚‚‚Cl, O-H‚‚‚Cl, and S-H‚‚‚Cl hydrogen bonds around the chloride ion in each of the compounds, as determined from the crystal structures. [27][28][29][30] The data shown indicate a possible trend: as the number of hydrogen bonds to chlorine increases from one through four, the Value of C Q decreases. An isolated chloride anion should exhibit no EFG due to its spherical symmetry; similarly a chloride ion with no opportunities for hydrogen bonding may exhibit a very small quadrupolar coupling constant, e.g., C Q ( 35 Cl) ) 0.8 MHz for calcium chloroapatite.…”

“…L-Cysteine methyl ester hydrochloride, Lcysteine ethyl ester hydrochloride, and quinuclidine hydrochloride were purchased from Sigma-Aldrich and used without further purification. For all of the compounds studied, X-ray or neutron diffraction studies [27][28][29][30] indicate that there is only one chlorine site and all spectra were analyzed as such. Compounds were powdered and packed into rotors for solid-state NMR spectroscopy.…”

“…25,79 The chloride anion in tris sarcosine hydrochloride possesses three hydrogen bonds to nitrogen atoms; this results in a reduced value of C Q , 4.04 MHz. The availability of X-ray crystal structures for the analogous compounds L-cysteine methyl ester hydrochloride and L-cysteine ethyl ester hydrochloride, 28 in combination with the NMR data presented in Table 1, allows for a particularly insightful analysis of the effects of the local chlorine environment on the 35 Cl NMR parameters. The crystal structures of these two compounds are very similar, both crystallizing in the P2 1 2 1 2 1 space group, and both possessing three N-H‚‚‚Cl bonds of comparable geometry.…”

“…In particular, Yesinowski et al have remarked upon the potential application of high-field NMR techniques to investigate the relationship between the chlorine nuclear quadrupolar coupling tensor and the hydrogen bonding environment about chlorine in organic hydrochlorides. 25 We explore this relationship by comparing the 35 Cl NMR parameters to known crystal structures for the following set of compounds in which chloride anions exist in a variety of hydrogen-bonding environments ( Figure 1): L-tyrosine hydrochloride, 27 L-cysteine methyl ester hydrochloride, 28 L-cysteine ethyl ester hydrochloride, 28 quinuclidine hydrochloride, 29 and tris sarcosine calcium chloride. 30 The 35 Cl and 37 Cl electric field gradient (EFG) and chemical shift (CS) tensors are examined using a variety of experimental techniques at 9.4 and 18.8 T, including magic-angle spinning (MAS) NMR, Hahn-echo spectroscopy 31,32 on stationary samples, and, for some compounds, quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) or "spikelet echo" spectroscopy 33-38 on stationary samples.…”