New hydrophobicL-amino acid salts: maleates ofL-leucine,L-isoleucine andL-norvaline

Abstract

Crystals of maleates of three amino acids with hydrophobic side chains [L-leucenium hydrogen maleate, C6H14NO2(+)·C4H3O4(-), (I), L-isoleucenium hydrogen maleate hemihydrate, C6H14NO2(+)·C4H3O4(-)·0.5H2O, (II), and L-norvalinium hydrogen maleate-L-norvaline (1/1), C5H11NO2(+)·C4H3O4(-)·C5H12NO2, (III)], were obtained. The new structures contain C2(2)(12) chains, or variants thereof, that are a common feature in the crystal structures of amino acid maleates. The L-leucenium salt is remarkable due to a large number of symmetrically non-equivalent units (Z' = 3). The L-isoleucenium salt is a hydrate despite the fact that L-isoleucine is a nonpolar hydrophobic amino acid (previously known amino acid maleates formed hydrates only with lysine and histidine, which are polar and hydrophilic). The L-norvalinium salt provides the first example where the dimeric cation L-Nva...L-NvaH(+) was observed. All three compounds have layered noncentrosymmetric structures. Preliminary tests have shown the presence of the second harmonic generation (SGH) effect for all three compounds.

A large anisotropic plasticity of L-leucinium hydrogen maleate preserved at cryogenic temperatures

“…The temperature of N 2 was controlled (AE 0.1 K) using a 700 Series Cryostream Cooler from Oxford Cryosystems. The initial coordinates of the (l-LeuH + )ÁM À structure were taken from CSD (refcode VUKQAV; Arkhipov et al, 2015), where the (l-LeuH + )ÁM À structure was solved using the olex2.solve (Bourhis et al, 2015) program. The structure was refined at every temperature point with SHELXL (Sheldrick, 2015) using least-squares minimization with Olex2 GUI (Dolomanov et al, 2009).…”

“…This molecular salt is one of the examples of plastically bendable crystals (Arkhipov, 2015). Its structure was solved and described by Arkhipov et al (2015), pointing out that it 'shows interesting mechanical behaviour: mechanical action on crystals of (l-LeuH + )ÁM À results in elastic, and then plastic, bending' (Fig. 1).…”

Structure-forming units of amino acid maleates. Case study ofL-valinium hydrogen maleate

“…The presence of the protonated carboxyl group favours the formation of C 2 2 ð12Þ 1 chains along the c axis (Fig. 2), a motif common for most amino acid maleates (Table S1) (Arkhipov et al, 2015).…”

“…Crystallization of new amino acid salts receives much attention (Alagar, Krishnakumar, Mostad & Natarajan, 2001;Alagar, Krishnakumar, Nandhini & Natarajan, 2001;Rajagopal, Krishnakumar, Mostad & Natarajan, 2001;Alagar et al, 2002Alagar et al, , 2003Sun et al, 2007;Natarajan et al, 2010;Petrosyan et al, 2012;Arkhipov & Boldyreva, 2012;Arkhipov et al, 2013Arkhipov et al, , 2015Fleck et al, 2013;Fleck & Petrosyan, 2014). More than 20 salts of maleic acid with different amino acids have been documented, and this number is rapidly increasing (Table S1).…”

Metabolomics Study on Improvement of Mild Cognitive Impairment by SCPE: a UPLC-Q/TOF-MS Mass Spectrometric Study

“…Xylobiose can enhance the proliferation of intestinal bifidobacteria and improve gastrointestinal function [20]. L-leucine and L-leucine are the main products of amino acid metabolism and participate in the pathogenesis of neuroinflammation and mental disorders [21].…”