A novel convergent synthesis of the antiglaucoma PGF2α analogue bimatoprost.

The 17-phenyl PGF(2α) analogue bimatoprost (10a) is the most efficacious ocular hypotensive agent currently available for the treatment of glaucoma or ocular hypertension. A novel convergent synthesis of 13,14-en-15-ol prostamideF(2α) analogues was developed employing Julia-Lythgoe olefination of the structurally advanced phenylsulfone (+)-(5Z)-15 with an enantiomerically pure aldehyde ω-chain synthon (-)-(S)-16a. Subsequent hydrolysis of protecting groups and final amidation of the diol 26a yielded bimatoprost (10a). The main advantage of the current strategy is the preparation of high-purity bimatoprost (10a). The novel convergent strategy allows the synthesis of a whole series of 13,14-en-15-ol prostamideF(2α) analogues with the desired C-15 asymmetric center configuration from a common and structurally advanced prostaglandin intermediate (+)-(5Z)-15. The preparation and identification of two synthetic impurities, 15-epi isomer (10b) of bimatoprost and a new prostaglandin related amide (+)-(5Z)-18, are also described.

Development and validation of the stability indicating RP-UHPLC method for the determination of the chemical purity and assay of bimatoprost.

A simple, rapid and accurate ultra-high performance liquid chromatographic (UHPLC) method with a UV detection for the determination of the chemical purity and assay of bimatoprost (BT-1) was developed. The chromatographic separation was achieved with the use of an Acquity BEH C8, 150 × 2.1 mm, 1.7 µm reversed phase analytical column. The mobile phase consisted of 0.01% H3PO4: acetonitrile (initial conditions 80 : 20, v/v) was passed through the column at the flow rate of 0.7 mL min-1. The separation was carried out in the gradient elution mode. The presented method allows to separate ten potential impurities of BT-1. The full validation according to the ICH Q2 (R1) guidelines was carried out for five of the potential impurities while limit tests were performed for four BT-1 related substances. The performed validation tests proved the suitability of the method for its intended purposes. An additional LC/MS method was utilized for the identification of the unknown impurities in bimatoprost as well as the degradation impurities generated during the forced degradation studies.

Stability of sample solution as a crucial point during HPLC determination of chemical purity of temozolomide drug substance.

An HPLC method for determination of related substances in temozolomide drug substance was developed. Particular attention was paid to the stability studies due to the fact that temozolomide is unstable in a solution and quickly decomposes to its main degradation product 5-amino-4-imidazolecarboxamide (AIC). A mixture of diluted acetic acid and acetonitrile (4:1, v/v) as a diluent guaranteed lowering the decomposition of temozolomide in the solution. As it is not practically possible to fully eliminate the decomposition of temozolomide during an analysis, the mathematical correction of the results was proposed which allows to analyse almost five times more samples per week, comparing to the procedure without the application of the correction. The accuracy of the correction procedure was proved by investigating the recovery of AIC spiked to temozolomide solutions at different levels. Recoveries equalled 90-108% for AIC concentrations contained in the range of 0.30-1.80 µg ml(-1). The developed method was validated according to the current guidelines, proving the suitability of the method for its intended purpose.