alpha-Methyl-l-tryptophan methyl ester → Methyl alpha-methyl-D-tryptophanate

Participants

Reaction Steps

To a suspension of (±)-α-methyltryptophan methyl ester (150.0 mg, 0.646 mmol) in 50 mL of 50 mM sodium phosphate buffer pH 7.5 was added carboxypeptidase Y from Bakers Yeast (6.4 mg). The resulting suspension was stirred at ambient temperature. After 4 h, 75% conversion was observed by HPLC (C18 column, 254 nm detection, acid tR =9.0 min and ester tR =11.9 min). The reaction was extracted with 2×25 mL chloroform. The combined extracts were treated with brine, dried with magnesium sulfate, then concentrated in vacuo to yield (R)-α-methyltryptophan methyl ester (15.6 mg, 67.2 mmol, 10.4%). A portion of this α-methyl amino ester was derivatized with 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate (TAGIT). HPLC analysis of the resulting thioureas showed the (R,S)-diastereomer to be in >99% diastereomeric excess (C18 column, 254 nm detection, S,S)-diastereomer tR =15.9 min and (R,S)-diastereomer tR =16.8 min).

Provenance & Evidence