(S)-2,2,5,5-Tetramethylthiazolidine-4-carboxylic acid: a compound which exists in the amino acid rather than the zwitterion form

Abstract

The X-ray crystal structure of (S)-2,2,5,5-tetramethylthiazolidine-4-caboxyic acid, b, has been determined. Crystals are monoclinic, P 2 , , with cell dimensions a = 11.351(4) b = 8.303(2), c = 11.969(3) A, P = 116.69(2)", and Z = 4. The structure was solved by standard methods and refined to RI = 0.0774, R2 = 0.0670 for 2388 independent reflections.Compound 1 exists in the amino-acid form as shown by two distinctly different C-0 bond lengths, 1.209 and 1.309 A, typical of the COOH group, and by the positions of the hydrogen atoms. The amino-acid form of 1 found in the solid also exists in solution as shown by infrared and Raman spectra. ' The mass spectra, and 'H and "C nmr spectra are reported, as well as detailed infrared and Raman spectra for the title compound and several deuterated species. [Traduit par le journal]

U,l-4a,5,6,7,8,8a-Hexahydro-4-phenyl-8a-(trimethylsiloxy)-4H-1,2-benzoxazine 2-oxide

“…The OIN202C3 unit is planar, consistent with an sp 2 N atom, but the angles at N2 are markedly distorted from the ideal 120 ° . While the internal ring angle is close to the expected value, the angle between the N2-O2 group and the N2-O1 single bond is closed up, with consequent increase in the angle between the two double bonds, features which we and others have observed in carboxylic acids (Howard-Lock, Lock & Smalley, 1985;Howard-Lock, Lock, Martins, Smalley & Bell, 1986;Howard-Lock, Lock, Martins, Faggiani & Duarte, 1987). The N2-C3-C4 angle is also greater than 120 ° [125.5 (3) ° ] consistent with some conjugation between N2-C3 and C3-C4.…”

Structure of 5,5-dimethyl-2-phenylimino-Δ3-1,3,4-thiadiazoline from oxidative cyclization of a thiosemicarbazone

“…(1.745(5) A) is significantly shorter than C5-S1 (1.827(4) A), and the former distance lies outside the ranGe we have observed in thiazolidine rings (1.784(5)-1.869(6) A) (14,15). The difference is in the expected direction since an sp' carbon atom is smaller than an sp3 carbon atom (0.743 vs. 0.763 A) (16).…”

Amino acid/zwitterion equilibria II: vibrational and NMR studies of substituted thiazolidine-4-carboxylic acids

“…In L-cysteine it has been assigned to 678 cm and it has been concluded that substituents on carbon atoms adjacent to sulfur cause a decrease in the stretching frequency of the C-S bond (7). Bands in the region of 680 and 600 cm, and 630 and 540 cm, are so assigned.…”