Salts of Tryptophan with p-Toluenesulphonic Acid and Camphorsulphonic Acids

Sayed, Amina; Jacobs, Ayesha

doi:10.1007/s10870-015-0627-6

Cited by 1 publication

(3 citation statements)

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“…Even the chirality modification is not observed during cocrystallization with chiral D-(R)-mandelate. 33 It is well documented that reversal of chirality is usually driven by different types of noncovalent interactions, packing patterns, and methods of preparation. 45 It should be noted that the structural motif of TRP adducts usually exhibits charge assisted…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Such a chirality reversal phenomenon is not observed in previously reported salts or cocrystals of TRP. Even the chirality modification is not observed during cocrystallization with chiral d -( R )-mandelate . It is well documented that reversal of chirality is usually driven by different types of noncovalent interactions, packing patterns, and methods of preparation .…”

Section: Resultsmentioning

confidence: 99%

“…However, despite the possibilities of all these interactions, supramolecular host–guest complexes of tryptophan are limited. A recent study reported that there are 12 structures with zwitterionic tryptophan: nine of them of TRP, one of d -tryptophan with naproxen, and the remaining two are of pure dl -tryptophan. − Additionally, the number of structures with cationic TRP is also limited. − The indole ring of TRP is usually difficult to ionize, and only strong acids or bases can protonate or deprotonate the ring. Thus, the reactivity of the amino acid is mainly dependent on the −COOH and −NH 2 group.…”

Section: Introductionmentioning

confidence: 99%

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Influence of the Local Chemical Environment in the Formation of Multicomponent Crystals of L-Tryptophan with N-Heterocyclic Carboxylic Acids: Unusual Formation of Double Zwitterions

Das

Srivastava

2017

Crystal Growth & Design

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Formation of multicomponent crystals (MCCs) of L-tryptophan (TRP) with N-heterocyclic carboxylic acids such as 2-picolinic acid (PA) and its 3- or 4-substituent isomers (nicotinic acid or isonicotinic acid), pyrazinecarboxylic acid (PZCA), 2,3-pyrazinedicarboxylic acid (2,3-PZDCA), 2-quinaldic acid (QA), and its 3-subsituent isomer (3-QA) is investigated in this manuscript. The investigation results in four multicomponent solid forms of the amino acid with coformers where the electron withdrawing functional group (−COOH) is present in the ortho-substituent to N-heterocyclic rings. The isomers of PA or QA having −COOH at the meta- or para- position failed to produce new phases. These solid phases were identified by powder X-ray diffraction results, and the MCCs derived from 2-picolinic acid (1) and 2,3-pyrazinedicarboxylic acids (3) were further characterized with single crystal X-ray diffraction. The crystal structure of TRP-PA (1) reveal a rare form of cocrystal where both the amino acid and the picolinic acid are in zwitterionic form. Further, in our surprise, the amino acid appears to undergo change in absolute configuration during cocrystallization. Crystal TRP-2,3-PZDCA (3) is observed as a salt where the amino acid exists in cationic form, and the carboxylic acid exists in anionic form. It is observed that the complementary H-bonding between the py-N/ortho- −COOH of the coformers with the α-NH3 +/α-COO– group of L-tryptophan primarily drives the cocrystallization process. Density functional theory calculations support the experimental observations as lower total energy and higher interaction energy values are obtained for the successfully synthesized MCCs. The solid state fluorescence of TRP (known as intrinsic fluorescence probe) shows that 2,3-PZDCA is an effective quencher.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%