Proton Magnetic Resonance Spectra of Malic Acid and its Salts in Deuterium Oxide^1,2

Stereochemistry of carboxylate complexes. Crystal structure of (-)598-malatodiaquomanganese(II) hydrate

“…solutions of alkali metal malates using NMR spectroscopy. [14][15][16] On the other hand, conformer B is the principal species observed in an NMR study of the zinc(II) complex.16 This conformation is favored by chelation of the hydroxyl oxygen and both carboxylate groups to the zinc(II), and is the one found in single crystals of (-)-malatodiaquozinc(II) hydrate from a crystal structure investigation.4 This same malate conformation is found in the crystalline cobalt(II) and calcium complexes which, of course, have similar ligand-metal coordination. In the manganese(II) compound the rotamer observed is A. In contrast to the malate complexes of zinc(II), cobalt(II), and calcium the terminal carboxylate does not close to form a six-membered chelate ring with Mn(II).…”

Analysis of Proton Magnetic Resonance Spectra of Cysteine and Histidine and Derivatives. Conformational Equilibria1

“…A similar trend has been observed in these and other amino acids,6-8 as well as in malic acid. 19 In order to discuss vicinal coupling constants, it is necessary to consider the three classical staggered forms of ethanes. As drawn for cysteine these are shown in Figure 1.…”

“…experiment performed on the solid acid with assumed trans-carboxylic acid groups,20 it now appears that enzymatic hydration of fumaric acid occurs in a trans manner so that the deuterated malic acid is erythro,21 In solution the monodeuterated malic acid exhibits the same highest field hydrogen as the normal acid, as well as the higher coupling constant with the -hydrogen. 19 Thus the high-field proton we have designated HB must be as labeled in Figure 1. This labeling for cysteine depends upon its similarity with malic acid and seems to be the best choice at this time.…”

High-resolution nuclear-magnetic-resonance spectra of hydrocarbon groupings II. Internal rotation in substituted ethanes and cyclic ethers

“…In a very recent paper on malic acid, HOOC(OH)HC. CH2COOH, and its deri vatives Alberty & Bender (1959) have concluded th a t a predominantly trans pair of hydrogen atoms has a coupling constant of 3 to 4-5 c/s, and a predominantly gauche pair has a value of 7 to 10 c/s. These assignments are the reverse of those expected from the present work on the halogen substituted ethanes, and it seems most probable th a t the relative stabilities of the different rotational isomers in solution differ from those assumed by analogy with the crystalline state.…”