Letter: Enhancement of optical rotation of levodopa by cyclization.

  title={Letter: Enhancement of optical rotation of levodopa by cyclization.},
  author={Lester Chafetz and T. M. Chen},
  journal={Journal of pharmaceutical sciences},
  volume={63 5},
Abstract The optical rotation of levodopa is an important purity criterion, since it provides the only means to control the presence of the allegedly toxic and therapeutically inactive D-isomer. The specific rotation, [α]D 25 , of levodopa is only about − 12°, which is insufficient to control optical purity. Barooshian et al. (1) proposed a TLC limit test for d-dopa in levodopa, involving conversion of the enantiomers to diastereomeric dipeptides. Jouin and Saias (2) and Coppi et al. (3… 
8 Citations
Determination of related substances of levodopa including the R‐enantiomer by CE
A CE assay for the simultaneous determination of the impurities of levodopa listed in the European Pharmacopoeia including the (R)‐enantiomer was developed and validated and was applied to determine the purity of several samples oflevodopa including the chemical reference substance of the European Pharmaceutical reference substance.
A review of the application of chiroptical methods to analytical chemistry.
  • A. Gergely
  • Chemistry
    Journal of pharmaceutical and biomedical analysis
  • 1989
Phenolic Cyclization of Epinephrine, Metaproterenol, Metaraminol, Phenylephrine, and Terbutaline with Formaldehyde
An exploratory study of the rates of cyclization of the title compounds with formaldehyde to 1,2,3,4-tetrahydroisoquinolines (THIQs) was performed using high-performance liquid chromatographic (HPLC) methods, finding terbutaline reacted significantly slower than the other compounds.
Variations of optical rotation of naproxen: polarimetric determination in the presence of nonchiral basic compounds.
The polarimetric determination of naproxen in heterocyclic, aromatic and aliphatic nonchiral basic solvents is an example of optical rotation enhancement of a chiral drug
Optical rotation enhancement of L-carbidopa by reaction with aromatic aldehydes.


Quantitative determination of D-dopa present in levodopa samples.
A method based on the ability of an L-amino acid decarboxylase, present in a Streptococcus faecalis suspension, to convert quantitatively L-dopa to dopamine while D-dop remains unchanged is reported.
[Enhancement of optical rotatory power of L-DOPA].