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New hydrophobic L‐amino acid salts: maleates of L‐leucine, L‐isoleucine and L‐norvaline
Author(s) -
Arkhipov Sergey G.,
Rychkov Denis A.,
Pugachev Alexey M.,
Boldyreva Elena V.
Publication year - 2015
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229615010888
Subject(s) - chemistry , norvaline , amino acid , isoleucine , hydrogen bond , salt (chemistry) , leucine , stereochemistry , organic chemistry , molecule , biochemistry
Crystals of maleates of three amino acids with hydrophobic side chains [L‐leucenium hydrogen maleate, C 6 H 14 NO 2 + ·C 4 H 3 O 4 − , (I), L‐isoleucenium hydrogen maleate hemihydrate, C 6 H 14 NO 2 + ·C 4 H 3 O 4 − ·0.5H 2 O, (II), and L‐norvalinium hydrogen maleate–L‐norvaline (1/1), C 5 H 11 NO 2 + ·C 4 H 3 O 4 − ·C 5 H 12 NO 2 , (III)], were obtained. The new structures contain C 2 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.