Optical Resolution of Dl-Valine, Dl-Leucine, and Dl-Isoleucine by Formation of Adduct with l-Phenylalanine

Abstract

An alkaline solution containing l-phenylalanine (l-Phe) and one of Dl-valine, Dl-leucine, and Dl-isoleucine is allowed to selectively form a precipitate composed of l-Phe and the aliphatic d-amino acid by adjusting the pH of initial solution to around 5.5 with hydrochloric acid. 1H NMR spectra in deuterium oxide, elemental analyses, and infrared spectra of the precipitates indicate that they are adducts of the aliphatic d-amino acid and l-Phe in the molar ratio of 1:1. The free aliphatic Dl-amino acids with high optical purity (84–100%) may be recovered from the adducts in 49–63% yield. An attempt was made to obtain both the aliphatic d- and Dl-amino acids by using an aqueous solution containig the aliphatic Dl-amino acid and l-Phe as an initial solution. The aliphatic l-amino acids obtained had optical purity of 47–85%.

X-ray studies on crystalline complexes involving amino acids and peptides. XXI. Structure of a (1:1) complex between L-phenylalanine and D-valine

“…This appeared to point to the possibility, in favourable situations, of chiral separation without the aid of external agencies even in a system containing equal numbers of D and L amino-acid molecules. However, chiral discrimination of the opposite type was indicated by Shiraiwa, Ikawa, Sakaguchi & Kurokawa (1984), who showed that L-phenylalanine preferentially forms complexes with D isomers of amino acids which have aliphatic side chains. The crystal structure of one such complex, namely, that between L-phenylalanine and D-valine, is reported here.…”

“…* Experimental. The crystals were grown by the method described by Shiraiwa, Ikawa, Sakaguchi & Kurokawa (1984). Unit-cell parameters were refined on a CAD-4 computer-controlled diffractometer using Mo Kte radiation employing 25 reflections in the range of 6-19 ° .…”

Preparation and isolation of 2-methylamino-3-phenylpropanoic acid enantiomers using selective crystallization

“…We reported optical resolution of DL-␣-amino acids with hydrophobic side chain via molecular compound formation with LPhe. 8,9 Therefore, the optical resolution of (RS)-MPP was attempted using L-Phe as a resolving agent. However, only (RS)-MPP was crystallized from an aqueous solution containing (RS)-MPP and L-Phe.…”

“…We 5 reported the optical resolution and asymmetric transformation of (RS)-MPA via salt formation with (1S)-10-camphorsulfonic acid [(S)-CS], which is an extremely strong acid. In addition, ␣-amino acids with hydrophobic side chain [7][8][9] have been reported to form molecular compounds with optically active MAN and phenylalanine (Phe). Based on these facts, we attempted to obtain both (R)-and (S)-MPP by optical resolution of (RS)-MPP without synthetic transformation into its derivatives.…”