Correction to: New crystal structures of fluorinated α-aminophosphonic acid analogues of phenylglycine

Correction to: Structural Chemistry.

https://doi.org/10.1007/s11224-019-01483-x

Corrections are needed to the original version of this article. The in-text citations of figures in the section “NMR spectra characterization” are not in sequential order. Moreover, the sequence of figures. 3-8 does not coincide with that in the text.

- Fig. 3. should show ¹H NMR spectrum, instead in the original paper ¹H NMR spectrum is presented in the Fig. 8.

- Fig. 4. should show ¹³C NMR spectrum, instead in the original paper ¹³C NMR spectrum is presented in the Fig. 3.

- Fig. 5. should show 2D NMR ¹³C, ¹H - HMQC spectrum, instead in the original paper 2D NMR ¹³C, ¹H - HMQC spectrum is presented in the Fig. 6.

- Fig. 6. should show ¹⁹F NMR spectrum, instead in the original paper ¹⁹F NMR spectrum is presented in the Fig. 4.

- Fig. 7. should show ³¹P NMR spectrum, instead in the original paper ³¹P NMR spectrum is presented in the Fig. 5.

- Fig. 8. should show 2D NMR ³¹P, ¹H - HMQC spectrum of the compound 1, instead in the original paper 2D NMR ³¹P, ¹H - HMQC spectrum is presented in the Fig. 7.

The corrected discussed section should read:

NMR spectra characterization

Due to low solubility in organic solvents, D₂O with one drop of NaOD was used as solvent. ¹H, ¹³C, ¹⁹F and ³¹P NMR, 2D NMR ¹³C,¹H – HMQC and 2D NMR ³¹P,¹H – HMQC spectra of the representative compounds (1) are showed. Doublet signal on the ¹H NMR spectrum at 3.75 ppm with ²J(_H-P) = 15–16 Hz, is a characteristic feature of these compounds and has been assigned to the methene hydrogen of the CHP fragment. The exchangeable N-H and OH proton signals appears as broad singlet at 4.68 ppm. The aromatic protons CH_ar from phenyl ring resonates in the expected region from 6 to 8 ppm (Fig. 3). As a consequence of proton-proton and proton-fluorine (in compounds 2, 3 and 4 with substitution of hydrogen atoms by fluorine atoms in aromatic moiety) the multiplicities of these signals are observed. On the ¹³C{¹H} spectrum (Fig. 4) characteristic doublet at around δ = 55 ppm with large value of coupling constant (¹J_(C-P) = 128.5 Hz) is generated as a result of interaction of the carbon atom directly related to the phosphorus (CHP). The two-dimensional spectrum ¹³C,¹H – HMQC (Fig. 5) confirm correlations of that signal with doublet in proton spectra ²J(_H-P). The quaternary carbon atom of trifluoromethyl moiety is visible at 124.54 ppm as doublet of quartets with two coupling constant: first high ¹J_(C-F) = 271 Hz and second very low about 1 Hz coupling as probable result from additional correlation with phosphorus atom (Fig. 4-B). In a similar manner resonate carbon atom directly bounded to CF₃ moiety, which was detected also as doublet of quartets at 127.43 ppm and the coupling constants occurs in the range: ¹J_(C-F) = 32.0 Hz and ²J_(C-F) = 2.9 Hz (Fig. 4-A). The remaining signals have been assigned to phenyl ring carbon atoms and their multiplicity is associated with the presence of fluoro substituents in aromatic rings. ¹⁹F{¹H} NMR spectra affirm presence of fluorine atoms in the structure and resonated in the expected region as multiplets for compounds 2, 3 and 4 and as singlet for CF₃ moiety for compound 1 (Fig. 6). Fluorine atoms substitution in the aromatic ring contribute to multiplicities of phosphorus signals on the ³¹P{¹H} NMR spectra and long-range couplings between P-F atoms are very good visible by 4, 5, 6 or even 7 bonds. In the case of compound 1 quartet with low coupling constant of ⁷J_(P-F) = 2 Hz is observed (Fig. 7). The 2D NMR ³¹P, ¹H – HMQC spectrum verified interaction of the methene hydrogen (²J_(H-P)) with phosphorus atom in CHP skeleton (Fig. 8).

The corrected sequence of the figs. 3-8 should be:

Fig. 3

¹H NMR spectrum of the compound 1

Fig. 4

¹³C{¹H} NMR spectrum of the compound 1. Extension of quartet signals C_ar-CF₃ (A) and CF₃-C_ar (B) have been showed as blue peaks and pink peaks, respectively

Fig. 5

2D NMR ¹³C,¹H – HMQC spectrum of the compound 1

Fig. 6

¹⁹F{¹H} NMR spectrum of the compound 1

Fig. 7

³¹P{¹H} NMR spectrum of the compound 1. The long-range couplings between phosphorus and fluorine generate quartet signal

Fig. 8

2D NMR ³¹P,¹H – HMQC spectrum of the compound 1

The authors apologize for the oversight and further state that the changes made to the in-texts citations and sequence of figures don’t have an impact to the overall outcome of the study.