I have the 1H, 13C, and DEPT spectra of an unknown compound, listed in text form below, but I have also attached original images of the spectra. I know that it is an amino acid that has a cyclic structure and a relative molecular mass of 145. I'm supposed to deduce the structure, but am having some trouble with it:
1H NMR (in D2O): 4.2 ppm (1H, s), 3.85 ppm (1H, dd), 3.2 ppm (2H, m), 2.1 ppm (1H, d), 1.8 ppm (3H, m) (image of spectrum)
From the spectral data, I can tell that the compound doesn't have an aromatic ring, but beyond that I don't know how to proceed. Unfortunately, although it would be really helpful, I'm not able to determine the coupling constants in the 1H spectrum.